Bottle Body Characteristics & Mold Seams

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INTRODUCTION

The subject matter of this page is a somewhat mixed bag of physical features or characteristics that are found on the major portion of a bottle - the body, including the shoulder and neck.  Since this site does not have separate pages or sections to specifically cover the shoulder and neck of bottles, they are combined in with the bottle body characteristics because of the commonality of features they all share.  When referring to the "body" of a bottle on this page, it is meant to mean body, shoulder, and neck unless otherwise noted.  On other pages, these three morphological parts of the bottle are considered separately.

The body of a bottle has an assortment of characteristics or diagnostic features that can assist a person trying to date or at least tell a more complete story of a given bottle.  The structure of this page covers three main categories of bottle body related features.  The first category encompasses those that are induced by some process related to the manufacture of the bottle, excluding mold induced features.  This includes various glass character features (e.g., bubbles, whittle marks) as well as bottle body attributes of bottles produced without a mold, i.e. free-blown bottle bodies.  The second category includes the characteristics that are caused or induced in some way by the mold or molding process.  This is the biggest category since most bottles manufactured during the time span covered by this website (early 1800s to 1950s) were produced in molds.  The final category includes features induced to the bottle body after the blowing and molding has taken place, i.e. post bottle production features.

These categories are somewhat arbitrary since there is overlap between them and just about everything discussed here is related to the overall manufacturing process which produces a finished bottle.  These categories do, however, lump similar processes together in a way that may help visualize how certain attributes of a bottle are related.

NOTE:  If unsure of some of the terminology used on this page related to the physical features of bottles, visit the General Bottle Morphology page.  That page includes an illustration of a somewhat stylized "typical" bottle with the different physical "parts" (morphological features) pointed out; parts which are often easier to visualize than describe.

A. Manufacturing (non-mold) Based Body Features

Free-blown bottle bodies

Free-blown bottles were produced without the aid of a mold, being instead formed and shaped by the skills of the glassblower using manipulation of the blowpipe, various simple hand tools, a hollowed out block, and usually a flat table called a marver.  Free-blown utilitarian bottles found or made in the U.S. typically date from before the American Civil War (early 1860s and prior) and of course can be much older than that.  The were rarely produced after the 1860s by American glass companies producing utilitarian bottles but the technique is still likely being used to some degree for specialty or artist bottles (Toulouse 1969a; empirical observations).  The following are the primary characteristics of a free-blown bottle taken from Jones & Sullivan's Glass Glossary (1989):

• The bottle formed without a mould will generally not be symmetrical in body, shoulder, neck or base.
• There are no mold seams, no embossing, no moulded decorations, and the exterior glass surface tends to be smooth and glossy, patinated areas excepted.
• The lines of the bottle will not be sharp, but will flow.
• Although free forming of glassware can produce some of the most elaborate shapes, being free from the confining borders of the mould, simple globes and elongated shapes are the easiest to form free-hand in quantity, so that free-blown commercial containers are most likely to be these shapes.
• There is a tendency for the glass to be evenly distributed in the various areas of the bottle.

One additional observation is that the glass at the heel or base edge of a free-blown bottle will tend to be somewhat thicker than the rest of the bottle which will be fairly evenly distributed (last "bullet" above).  In addition, the heel and extreme lower body of a free-blown bottle will often flare out somewhat with the base diameter being slightly wider than the average diameter of the bottle body.  Both of these features are related and caused by a combination of the action of the tool that formed the push-up inside the base and the hot glass flowing or sagging as it was not contained by any mold surface (Jones 1983).  This feature shows most distinctly with the bottle to the right in the picture.  Bottles produced with a block and/or marver are typically (always?) round in cross-section and hard to differentiate from a purely free-blown bottle, though the latter method produces bottles with generally less symmetry.  Block/marver produced bottles are considered with free-blown bottles here since they are largely indistinguishable from free-blown items and are still produced almost purely by the skill of the glassblower without the use of a dip or full-sized mold, both of which are covered later on this page (Kendrick 1968; Deiss pers. comm. 2005).

The photo to the right above (click to enlarge) shows two free-blown European-made bottles in shapes that were also likely made and used in the U.S. also.  Both bottle bodies show varying degrees of non-symmetry.  The dark olive green bottle to the left is likely a Dutch (possibly English) generic liquor bottle most likely made between 1750 and 1800 (McKearin & Wilson 1978; Jones 1986).  It's symmetry indicates very good craftsmanship and control by a master glassblower.  The bottle to the right in the picture is an early to mid-19th century French "Muscat" (a sweet dessert wine) bottle that exhibits very asymmetrical form and a distinctly flared out heel. 

The photo to the left is of the bases of both bottles showing the lack of symmetry from another angle.  Both bottles exhibit varying amounts of an out-of-round shape, with the French bottle being much more asymmetrical than the other bottle although the French bottle is a generation or two "younger" than the Dutch bottle.  Mold-blown bottles can be asymmetrical due to sloppy craftsmanship, but are typically uniform and symmetrical.

One note of caution is that turn-mold bottles will, like free-blown bottles, have no evidence of mold seams either.  However, turn-mold bottles will be very symmetrical, always be round, and just not "look" as old as free-blown bottles.  This is an important distinction to make since free-blown bottles usually date prior to the Civil War and often are much older than that; turn-mold bottles usually date from the late 19th century to early 20th century.  They are discussed in more depth under the "Mold Induced Body Features" section later on this page.
 

Body glass imperfections

The body of a bottle can have a host of different features or imperfections that can be observed and classified.  Some features were induced on purpose like the whimsical spiral of glass on the upper half of the likely English made ale bottle pictured to the right, which dates from the late 19th century or even possibly the early 20th century.  Click applied glass ale bottle to see this entire bottle which likely had the spiral added when the finish glass was applied; it has a true applied finish.  Many other body features are not intentionally induced.  These include stretch marks, "straw" lines, slumps and sagging spots, bumps, folds, thin and thick spots in the glass, foreign material imbedded in the glass, and others.  Bubbles and whittle marks are also considered imperfections in the glass, but are covered in separate sections below.  In the glassmaking world these are all considered as defects or "faults" and were not desired by glassmakers though they do not always compromise the utility of the bottle.  Many of these flaws can be found in either mouth-blown and machine-made bottles, but some are fairly specific to one or the other (Tooley 1953; Kendrick 1968).  The following is a listing and description of the most common imperfections along with a discussion of the utility the feature offers in gaining information about the bottles these imperfections are found on.

"Stretch" Marks:  Bottle glass can have varying lines, ripples, or twists in the glass that are the result of the irregularities in the glassblowing process, i.e. twisting of the blowpipe, the way the glass was initially gathered, glass temperature differentials, and other reasons.  In the glass making trade these type irregularities in the glass were called "cords", "washboards", or "laplines" but these terms were more in reference to ripples and such in the body of a bottle (Tooley 1953; Kendrick 1968).  As used on this website, the term "stretch marks" refers to these marks found on the outside surface (primarily) of the bottle neck and to a lesser degree, the shoulder. 

The picture to the left shows typical, though distinct, stretch marks in the neck of an early American liquor flask - the most common location for stretch marks in a mouth-blown bottle.  Click Stoddard double eagle flask to view picture of this entire bottle which is a pint flask likely made at the Granite Glass Works (Stoddard, NH.) between 1846 and 1860 (McKearin & Wilson 1978).  Neck/shoulder stretch marks are usually quite diagnostic of a mouth-blown bottle as they are rarely observed on machine-made items, though machine-made bottles - especially earlier ones - are observed with ripples or irregularities in the body of the bottle.  The following empirical observations have been made in regards to the presence of stretch marks:

• In mouth-blown bottles, stretch marks are quite common in the bottle neck and to a lesser degree, the upper shoulder.  Various wavy or irregular glass imperfections are quite common in the bodies of mouth-blown but usually do not exhibit the surface striations like those found in the neck.
• There were several interrelated causes of neck/shoulder striations all related to forces exerted on the hot glass by glassmakers tools.  First was by the twisting of the blowpipe during the inflation process, particularly when the body of the bottle was "locked" in place in the mold and the glassblower rotates the blowpipe even slightly.  Another likely cause was during the removal of the bottle from the blowpipe (shearing, cracking or bursting off) due to torque differences on the still pliable glass between the blowpipe on one end of the bottle and the pontil rod or snap case at the base.  It was also a common result of work being performed on the neck of a bottle with the tongs or pucellas.  These tools were used for "necking" the bottle which was a hand tooling process done to ensure the neck was as narrow as required and to minimize the amount of glass left on the blowpipe when removed (Boow 1991).
• Stretch marks in the neck - particularly the upper portion of the neck - are most common on bottles with true applied finishes.
• On bottles with tooled finishes, neck stretch marks are less common than with true applied finishes and usually only below the reach of the lipping tool on the outside of the bottle neck since the tooling action itself would wipe out the marks in the tooled area of the finish and extreme upper neck.
• If one finds a fragment of a bottle neck with distinct stretch marks as described here, it is almost surely a mouth-blown bottle with manufacture prior to the mid-1910s.

If there are bubbles in the neck of a mouth-blown bottle with stretch marks, they will almost always follow the twist and trend of the stretch marks.  This is, as described above, a function of the glassblower twisting the neck glass during some part of the bottle making process.  Sometimes this twisting distorts the glass of the neck significantly.  The picture to the right is of a small schoolhouse ink with a cracked-off finish dating from about 1880.  It has a large stretch mark running from the right shoulder up through the middle of the neck in the picture.  This mark manifests itself inside the bore of the bottle as a distinct, rounded hump that is obvious looking down the bore.

Straw Marks or Lines:  Straw marks are hair fine wavy lines on the surface of the body (and/or neck and base) glass that can be alone or in patterns.  This very fine lines are seemingly (or actually) etched into the glass surface and can be felt as a sharp "tick" when running ones fingernail across the surface.  There are at least two reasons for straw marks on bottles, either of which are about impossible to tell apart without knowing something about the origin of the bottle itself.

The early American snuff bottle pictured to the left has various straw marks running around the sides and shoulders (none on the base).  This bottle was produced in a dip mold as there are no mold seams visible on the bottle though it has obvious form shaping that was largely impossible to do this well freehand.  This bottle is believed to have never been buried (i.e. has wear on the base from sitting somewhere for a long period and the provenience of the item) so these type of straw marks are likely related in some way to the production process.  This most likely was a function of the way the glass was made (the batch components), though it could also be due to some unknown effect of the gathering or blowing of the glass or possibly related to the weathering of the glass surface by a humid atmosphere over time (next paragraph).  Straw marks on never buried bottles have only been observed by the author on earlier mouth-blown bottles.  Also see the unusual variation of straw marks pictured in the "Other glass imperfections" section below.

The other "type" of straw marks are related to being buried in the ground and the chemical weathering reaction between the soil and the glass surface.  These straw marks have nothing directly to do with production of the bottle though is quite connected to the chemistry of the glass.  Glass is made primarily of sand, soda, and lime with the soda content being the part that is leached out of the glass by contact with soil and moisture.  (This is called patination or staining and is covered later on this page.) These swirls are related to that deterioration though the exact reason for their conformation is unclear (Kendrick 1963).  The bottle pictured to the right is a Ross's Aromatic Tonic.  This ca. 1880 medicine bottle was definitely buried and excavated since it was heavily stained and subsequently "polished" to remove most of the staining.  The straw marks remain however.  It has an assortment of straw marks running around the sides of the bottle which show in the upper part of the embossing pattern.  In a side by side comparison with the snuff bottle above, the straw marks look almost identical.

There are no particularly useful dating opportunities related with straw marks (and patination in general) since they can be found on mouth-blown (buried or unburied) and earlier machine-made bottles that have been buried.  However, straw marks seems to be more common on mouth-blown items than machine-made, though that is likely just a function of time and the effects of it on glass.  Earlier (pre-1930s approximately) machine-made bottles tend to weather faster than earlier mouth-blown bottles due to a higher soda content of earlier machine-made glass composition and chemistry which was necessary for proper feeding into machines (Kendrick 1968). 

(Note:  If viewers of this section have additional information on this interesting phenomena, we would be interested in hearing about it - especially with bottles that appear to have been never buried.  The above is our best guess as to the reasons behind straw marks based on years of observations.)

Stones:  Also called "potstones" by collectors, "stones" and "knots" by 20th century glassmakers, and a "non-glassy inclusion" by some archaeologists (Scholes 1941; Dillon 1958; Jones & Sullivan 1989).  Since glassmakers used the term "stones" that is the preferred terminology here, though potstones is the most widely used term.  These are imperfections in the glass itself that are are usually the result of poor or incomplete melting of the glass batch components.  Other possible causes of stones are detached particles from the bricks in the walls of the glass furnace or the glass pot itself, both of which are gradually wore out over time by the intense heat of molten glass (Kendrick 1968).

The picture to the left shows a particularly large (1.1 cm in length) stone in the shoulder of a Lindsey's Blood Searcher (Pittsburgh, PA.) - a large patent medicine bottle that dates from between 1865 and 1875.  Most stones are smaller than this, but they vary in size from pinhead sized specks to larger than the one pictured (which is shown because larger ones are easier to photograph and see). 

Generally speaking, there is no precise dating information connected to the presence (or absence) of stones, though they are very common in bottles made prior to the 1870s and commonly noted in mouth-blown bottles that date prior to the 1890s.  After this time glass batch processes and chemistry made rapid improvements and stones became increasingly rare.  Stones are unusual in machine-made bottles, but do occur.  They are much more likely to be found in the earliest machine-made bottles, i.e. early 1900s up into possibly the 1920s.  After that time, stones are very rarely found (empirical observations).

Other glass imperfections:  There are many other bottle glass imperfections that include sunken, sagging, or bulging sides; uneven glass thickness particularly in the base; crooked necks; "orange-peel" surface texture; off color striations in the glass; and others.  (Bubbles and whittle marks are glass imperfections also, but covered separately below).  These forming defects are caused by a myriad of flaws in the glassmaking and glassblowing processes ranging from the temperature and chemistry of the glass to the skill or sloppiness of the glassblower and his helpers (and maybe even the day of the week like reportedly with automobile quality!).  

As one example of an inexplicable imperfection that one can run across, the picture to the right shows a strange variation of the previously discussed "straw marks" on a mid-19th century English-made bottle that was known to have been never buried (i.e. "attic found").  These lines have regular "railroad tie" type cross hatching lines included in what would otherwise be typical glassmaking induced straw marks.  How (or why) these marks were formed is unknown, but had to be related to the glassmaking process.  (Photo courtesy of Richard Martin, Harrisonburg-Rockingham Historical Society, VA.)  There is a possibility that these lines were caused by the bottle being blown in a fired clay mold as such lines have been reported by potters on their wares.  These unusual lines would be the plastic hot glass picking up the surface imperfections on the inside of the clay mold.  (Joel Williams pers. comm. 2008).

The following quote on bottle glass defects is taken from Grace Kendrick's excellent 1968 book on bottle making - The Mouth-Blown Bottle:

One of the major causes of defects in bottles is the nature of glass itself. It "sets up" too quickly!  As man is forming a bottle out of this pliant substance, it very suddenly turns rigid and resists any further manipulation.  The action works in reverse also, allowing the glass to suddenly turn TOO fluid when re-exposed to heat.  Further, the hardening and softening won't be uniform throughout the glass object, since thinner areas will cool more quickly than the thicker parts.

A typical defect caused by the short period between softening and hardening of the glass, is the distortion of the shapes of the bottles.  The necks may rise off-center, the lips may be non-round, the body of the bottle may slump or sag to one side.  The slumping may cause wrinkles or grooves to appear in the glass, or it may give a concave surface to one wall of the bottle.

Faulty temperature may also cause the glass not to conform to the mold, allowing hollow depressions to appear on the bottles.

There is little utility in discussing these miscellaneous bottle body flaws at length except except to say that they are much more likely to be found on mouth-blown than machine-made bottles and earlier bottles (in both categories) tend to have more glass flaws than later produced bottles.  The uniformity of machine manufacture - the precision of the machine itself in conjunction with better technology in all aspects of the glassmaking - eliminated many of the flaws that were common in earlier mouth-blown items.  Most notably is that the glass in a machine-made bottle is much more uniform with heavy uniform bases and relatively thick even walls.  Conversely, some mouth blown bottles will have base glass that is an inch thick on one side slanting off to paper thin on the other side (Kendrick 1963).

For more information on glass imperfections or forming defects, consult Tooley (1953) for machine-made bottles and Kendrick (1963 & 1968) and Munsey (1970) for mouth-blown bottles.
 

Bubbles in the glass

"Bubbles" are air or gas filled cavities within the glass.  See the image to the left for a close-up of a bottle with bubbles in atypically high quantity for illustrative purposes.  In the glass making industry, small bubbles were referred to as "seeds" and larger bubbles as "blisters."  Bubbles are caused by an assortment of irregularities in the production process, including a glass pot or tank that is too hot, a glass tank which is not full enough, glass cut-off or shearing irregularities, and various gob feeder problems.  The presence and/or amount of bubbles in glass is also related to where in the glass pot/tank the glass is drawn from for blowing (Tooley 1953). 

Very generally speaking, bubbles in the body of a mouth-blown bottle - if they have a distinctive orientation - tend to be vertically elongated reflecting the up and down stretching of the hot glass while being inflated.  (This phenomena seems much less distinct in machine-made bottles, though machine-made bottles on average have far fewer bubbles than mouth-blown bottles.)  Conversely, if the bubbles in the finish of a mouth-blown bottle with an applied finish have any distinctive orientation (most don't) they tend to be horizontal.  This is a product of the way the finishing glass was applied to the point where the blow-pipe was removed.  Specifically, the hot glass was added via a small gather made on a blowpipe or other tool as a variably thick (depending on the finish type and size desired) strip or "string" immediately below the cracked-off or sheared point of the neck as the bottle was rotated by another glassworker holding the bottle by the base with either a pontil rod or within a snap-case tool (Jones & Sullivan 1989).  Like body bubbles, mouth-blown tooled finish bottles tend to have vertically elongated bubbles since the glass of a tooled finish was blown with the remainder of the bottle, not applied after removal from the blowpipe (empirical observations).

Some authors have noted that the presence of a considerable number of bubbles are an indicator of manufacture prior to 1910 (mouth-blown and some machine-made bottles) and even more likely prior to 1904, which would have been primarily bottles of mouth-blown manufacture (Kendrick 1963).  Others, have noted that "the number and size of bubbles has absolutely no connection with the age of the glass"  (Jones & Sullivan 1989).  Both appear to be at least partially true. 

During the early 20th century glassmaking technology had improved enough so that the chemical reduction of bubbles in the molten glass was possible in bottles of any manufacture.  Specifically, arsenic or sodium nitrate was added to the glass to reduce bubble formation (Kendrick 1963).  Since the large majority of the bottles produced during and prior to the early 1900s were mouth-blown, the presence of a significant amount of bubbles is likely to be at most a weak dating indicator of relative age.  The author of this website has several mid-18th to early 19th century free-blown bottles that have few bubbles in the glass and bottles from the late 19th century that have hundreds of bubbles.

As the machine-made bottle era of the early 20th century progressed technology improved and glass homogeneity and uniformity also improved.  Besides glass chemistry improvements like those already noted, bubbles became relatively uncommon in machine-made bottles due to the machines drawing glass from the center of the glass vat instead of from the top where bubbles tended to congregate like foam on a beer.   By the end of the 1920s, machine-made bottles which have numerous and/or large bubbles did exist but were increasingly unusual (Berge 1980; Girade 1989; Lockhart pers. comm. 2003).  This feature is still, however, a tenuous one for dating since there are many earlier machine-made bottles (prior the 1920s) with few if any bubbles.  It is largely true that the presence of a large amount of bubbles in a glass fragment makes it likely that it was from a mouth-blown bottle, though without other diagnostic features evident it may not be possible to tell for sure (Kendrick 1963; Girade 1989; empirical observations).

One "type" of bubble that seems to be found only in machine-made bottles is shaped like an upside down "V", i.e. the narrow end of the "V" points towards the bottle finish (picture to the right).  It is unknown exactly what causes this shape of bubble, though it appears to be a result of the much higher pressures that a machine can exert over a man's lungs.  These type bubbles seem to be present primarily in earlier machine-made bottles, i.e. 1905 to through the 1920s and usually in bottles produced by the Owens Automatic Bottle Machine.  Since these machines brought the glass into the parison or blank (first stage) mold from below via suction (i.e. a created vacuum pulls the glass into the mold from above) the shape of this bubble makes sense as the larger middle portion would be distended upwards by the powerful suction action. 

The presence of this shape of bubble in the glass of a fragment is almost a sure indicator of machine-made manufacture, though most bubbles in machine-made bottles are not this shape.  It is common for a machine-made bottle to have a couple of the inverted "V" bubbles, with the rest being normal round or oval shaped (empirical observations).
 

Whittle marks

Whittle marks are a very descriptive term for a bottle body feature that generally has nothing whatsoever to do with its name.  The term "whittled" or "whittle marked" is a reference to a hammered or wavy surface to the glass that one could imagine was caused by the "whittle" marks of the mold maker on the inside surface of a wooden mold.  Early 19th century glass makers called this effect "ruffled glass" while later it was referred to as a "hammered look" (Toulouse 1966, 1969a).  See picture to the left.

Appealing though this notion is, the vast majority of molds used to produce bottles during the era covered by this webpage (1800 through the 1950s) were made of various metals, or in the earlier years, fired clay (Van den Bossche 2001).  Although wooden molds were extensively used in the very early days of bottle making (pre-1800 up until the 1850s) and continued to be used for some applications until the early 20th century, including for the block in free-blowing, wood had too short of a life span to be of much use for most industrial bottle making where the temperature of molten glass was 2000°F and wood burns at about 1/4th that temperature (Whitall Tatum 1880; Toulouse 1966; Lohmann 1972; Boow 1991).  It is believed impossible to visually determine that a bottle was blown in a wooden mold since these type of molds had to be kept very wet in order to avoid premature burn-out or even ignition when the hot glass hit the wood.  Due to the water, steam was formed in the mold creating a cushion that the bottle "rode" on between the glass and the mold surface (Scholes 1952).  This would not leave any trace of the mold surface texture and would likely preclude embossing on the bottle.  When used, wooden molds were often lined with clay, coal, pitch, and other materials to try to extend the life.  All were poor substitutes for metal molds (Atwater 1893; Toulouse 1966; Kendrick 1968; Lohmann 1972; Munsey 1970; Deiss pers. comm. 2005).

Whittle marks were actually caused by a reaction of the hot glass hitting the surface of a colder mold; cold relative to the temperature of the molten glass.  Molds needed to be red hot" to properly produce a bottle without the wrinkles or ripple-marks that are known as whittle marks (Scholes 1952).   This hammered look of mouth-blown bottles was also believed to sometimes be caused by the rolling the hot parison on the usually colder marver (Toulouse 1966).  In a sense, whittle marks are bottle "goose bumps."  As glassblowers were paid for the number of intact bottles blown, not by the surface quality of the items, there was little incentive to pay much attention to things like whittle marks or for that matter, bubbles in the glass or other largely non-impairing flaws (Toulouse 1966; Munsey 1970).   The August 1890 edition of the National Bottlers Gazette (a carbonated beverage industry publication) noted the following - "The hammered look that some bottles present is not a sign of weakness except so far as the appearance of the bottle is concerned.  The cause of this 'Hammered' appearance is that the glass has been put into a mould which has not been sufficiently hot, and the steam from the surface has imprinted itself upon the bottle."  The steam was from the water that metal molds were either sprayed with or dipped into periodically to cool them (Toulouse 1966).

Kendrick (1968) suggested that the term whittle marks, though inaccurate, should be retained because of its ubiquitous use and because "although the (term) may be misleading as to the true cause of the deformity, it represents a true picture in the mind's eye of how the marks appear."   This is not to say there have not been periodic debates over whether some whittle marked bottles actually do exhibit the signs of the wooden mold makers knife.  The most notable argument for this was put forth by the pioneering May Jones in Volumes 7 & 8 of her "The Bottle Trail" publications during the 1960s (Jones 1967).  However, as noted above, the steam caused by the hot glass vaporizing the moisture in a wooden mold would almost certainly preclude any subtle mold surface irregularities from expressing themselves on the bottle surface (Deiss pers. comm. 2005).  It is now believed that the vast majority - if not all - of the bottles exhibiting whittle marks are the result of the noted glass to metal mold reaction.

The bottle pictured to the above left exhibits an extreme level of whittle marks.  This is an Old Dr. Townsend's Sarsaparilla (New York, NY) that dates from the 1850s (Shimko 1969; Odell 2000).  This bottle was probably blown early in the day before the mold had warmed up much or after extensive cooling with water.  Though having whittle marks way more distinct than normal, this bottle makes a good illustrative item for showing this feature.  Most bottles having whittle marks exhibit them in less density and less distinctly than the pictured item.  As an example of more subdued whittle marks, click on the picture to the right.  This is a ca. 1865-1875 medicinal tonic bottle (C. G. PENDLETON'S / TONIC - the embossing is turned away in the picture) thought to be from Memphis, TN.  (Incidentally, whittle marks can be evident on any color of bottle; dark ones were used here since the dark glass surface photographs better.)

In the 20th century, much more attention was paid to all aspects of a bottles conformation and quality.  Whittle marks were, as Kendrick noted above, a deformity of the glass and something that 20th century bottle makers worked to eliminate.  They referred to whittle marks as "washboards", "brush marks", "wavy surface", "ripple-marks", "wrinkles", and probably other terms (Scholes 1952; Tooley 1953).  Some automatic machines pre-heated the molds (called a "hot mold" - molds are also cooled if too hot) though whittle marks are observed occasionally in machine-made bottles also.  These defects are less likely in fully automatic machines because they would run 24 hours a day rarely cooling off; the mold heat being supplied by the glass itself.  In addition, the cycling time from one bottle to the next was very short since machines in the mid-20th century were producing soda bottles at the rate of 30-125 (or more) per minute with one operator - hardly time to cool of much.  As a comparison earlier hand production operations produced about 1 bottle per minute with several people involved (Tooley 1953; Kendrick 1968; Jones & Sullivan 1989).

(Note: A similar bottle surface irregularity that is seen now then on mouth-blown bottles is what is termed an "orange-peel" effect or surface.  It is quite descriptive as it is a pebbly surface to the glass that very closely resembles the texture of orange peel.  This effect is probably caused similarly to whittle marks, though it is possible that at it is caused at times by the rough surface texture of a more crudely made or worn iron mold.)

Dating notes:  In general, there is little in the way of dating refinement or opportunities associated with whittle marks except that this feature is much more common on mouth-blown bottles than machine-made items and more common on earlier machine-made items (pre-1925 or so) than bottles made after that time.  If one has a fragment that exhibits distinct whittle marks it is most likely from a mouth-blown bottle though other diagnostic features would have to be considered in arriving at a reasonably narrow dating range (empirical observations).  (Since whittle marks are molding related - though not intentional - the subject could have been covered under the next section on "Mold Induced Body Features.")

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B. Mold Induced Body Features

Introduction

The large majority of bottles produced within the time span covered by this website (1800 to the mid-20th century) were produced in some type of metal mold (e.g., iron, brass, steel) though molds were also made of various woods, ceramic, fired clay, clay lined wood, soapstone, and likely other materials (Jones 1967; Lohmann 1972; Van den Bossche 2001).  Molds could range from the most simple - a dip mold which could just be a bucket or dug out hole in the floor of the glassworks - to the elaborate full sized molds with as many as 9 different mold sections (Toulouse 1969b).  Molds increased the production of bottles greatly since less skills and labor were needed to produce a bottle with a mold than for a free-blown bottle.  While forming the shape of the bottle, molds leave behind diagnostic "bread crumbs" that provide information on the manufacturing techniques used and often the age of a bottle (Kendrick 1968; Munsey 1970). 

The great 1908 image to the right is from a West Virginia glass factory and shows a "gaffer" (blower) at work to the far left with his crew.  This is a typical mouth-blown shop crew which included the "mold tender" boy (lower right) with a set of "tongs" in his right hand, the "gatherer" (behind gaffer) with the next gob of glass for the gaffer on a second blowpipe, and the "snapper up" (to the right standing) with a snap case tool in his left hand.  The caption to the photo is: "Glass Blower and Mold Boy. Boy has 4 1/2 hours of this at a stretch, then an hour's rest and 4 1/2 more: cramped position. Day shift one week: night shift next. Grafton, W. Va. Location: Grafton, West Virginia" (Lewis Hine photo, Library of Congress).

The following is quoted from The Illustrated Guide to Collecting Bottles (Munsey 1970) - probably the best general bottle book ever published:

The study of the seams and other markings found on bottles can be of great assistance in identifying the type of molds and tools used in the their manufacture.  Knowing when the various molds and tools were in common use provides a basis for the approximate dating of bottles...

With that lead-in, we move on to the major mold induced features found on the body of historic bottles.
 

Dip molds

The dip mold is a step up in technology from simple hand tool and marver manipulated free-blowing in the manufacture of bottles and was used for various types of glass manufacturing back into antiquity, beginning long before the era covered by this website.  A dip mold is a simple open top mold that was used to gain uniformity and consistency (and likely increased production) in the shaping of the bottle body and base.  A simple one-piece round bottle dip mold is illustrated to the left showing its open top and the slight narrowing taper from top to bottom necessary for the removal of the inflated bottle (Toulouse 1969b).  The illustration below shows 19th century glassblowers using dip molds (middle & right in image) that look like buckets, to help form their bottles.  Some dip molds were simply appropriately shaped holes dug into the floor of the glassworks (Kendrick 1968).  Dip molds were also used for shapes other than round, e.g., square, hexagonal, and octagonal (Jones 1986).

One-piece round dip molds would leave no classic narrow, raised mold seams on the body of the bottle (more below).  Two (or more) piece, shoulder height, round dip molds could potentially leave fitting joint induced vertical mold seams on the body of the bottle.  This appears to have been uncommon as the author of this website has never seen a dip molded round bottle with obvious side seams.  Although it surely occurred, it was possibly more common in the era prior to that covered by this website.  Multi-sided dip mold bottles (pictured below) may likely have been made from multi-part dip molds, though side seams showing the interface between the mold pieces are rarely seen, being either masked by the corner edges of the bottle or the bottle body was fire polished to the point that seams are unrecognizable.  Dip molds were made of a variety of materials including wood and harder materials like various metals, clay, and clay lined wood.  Wooden dip molds (a common pre-19th century mold material) had to be kept continuously wet in order to survive long the intense heat of molten glass.  This allowed steam to form in between the hot glass and mold surface causing the glass to "ride" on the steam cushion making the evidence of molding very difficult to distinguish from free-blown bottles, although this feature did make it easier for the bottle to be removed from the dip mold (Boow 1991).  Sometimes the expanding parison would touch the sides of wooden mold before the cushion of steam formed leaving ripples, though this feature may be impossible to positively distinguish the use of a wooden mold versus glass imperfections (e.g., whittle marks) caused in metal molds for other reasons (Tooley 1953; Kendrick 1968; Toulouse 1969b; Jones & Sullivan 1989; Van den Bossche 2001; Deiss pers. comm. 2005).

In use, the parison of glass on the end of the blowpipe is placed into the open top of the dip mold then blown and expanded to form the body of the bottle and giving the base at least its diameter and sometimes shape.  One-piece dip molds could produce about any cross section bottle shape - round, square, octagonal - but had to be designed to be removed from the top (i.e. slightly wider at the shoulder than base).  Two (or more) piece dip molds could theoretically have about any body shape (or even embossing) since the expanded bottle could be removed by opening the mold segments.  Though a dip mold could be made of multiple sections, according to Jones (1986) they were not designed to be open and shut.  Apparently, dip mold bottles were not body embossed and even base embossing is uncommon but not unknown (discussed below).  Once the body and base were fully expanded within the mold, the bottle was removed and the shoulder and neck formed to shape with glassblower skills and hand tools like a free-blown bottle.  The base may or may not receive hand forming to shape it, though in early dip molded bottles the base was usually pushed inwards with a tool to form a "push-up" or kick-up" (Jones 1986; Jones & Sullivan 1989).

The body of a round dip mold bottle will be very similar in appearance to a free-blown bottle except that a dip molded bottle will tend to be more symmetrical in shape with little or no distortion.  This includes the general lack of the flaring of the extreme lower body and heel that free-blown bottles will often (but not always) have.  (Click free-blown lower body to view a picture showing base flaring on an early to mid-19th century free-blown bottle.)  The body of a dip molded bottle will not have embossing.  Because of the surface contact with the mold the sides of a dip molded bottle body from the shoulder to the heel usually have some distinctly "ruffled" or vaguely textured look to it as compared to the glossy smooth, fire-polished surface of the shoulder and neck.  This type of surface glass discontinuity is a diagnostic feature of dip molded bottles, though it is not always obvious or apparent (Toulouse 1969b; Jones 1986).

Another method to often differentiate a dip molded bottle from a similar free-blown bottle is to look at the junction between the body and shoulder.  Dip molded bottles will very often have a distinct discontinuity in the glass appearance right at the break between the the body and shoulder due to the "blow-over" effect induced by the mold ending at that point; i.e. essentially an "end-of-the-mold" mark.  This shoulder discontinuity could also be considered as a type of mold seam, though not with the typical look of regular mold seams where two parts of a mold come together (Shafer 1969; Jones 1986; Deiss pers. comm. 2005).  This shoulder discontinuity is easier to see than describe and is shown distinctly in the picture at the following link - dip mold bottle shoulder - which is a close-up of the bottle to the left.  This is a dip molded ale or liquor bottle with a glass-tipped pontil scar that dates from the 1850s.  The picture also shows the glass surface texture difference between the body (slightly wavy or rough) and the shoulder (smooth and glossy). This shoulder mold seam or discontinuity can be observed on any shape of bottle that could be dip molded, though on square bottles (like discussed next) it is not usually as obvious as on a round bottle (empirical observations).

The square, dark olive green bottle to the right is a dip-molded "case" or "tapered" gin that dates from the mid-19th century (Shafer 1969).  This particular bottle was produced near the end of the dip mold era (see dating below) as it is not pontil scarred and was found in western Oregon in the context of immediate post-Civil War era items.  It is possibly American made, though that is impossible to say for sure.  The body of this bottle was dip molded in a square mold and has a faintly embossed cross on the base of the bottle - sure proof of molding.  Click base embossed cross to view a picture of the embossing.  Base embossed dip molded bottles are unusual though obviously occurring.  Click case gin shoulder close-up to view a close-up picture of the interface between the crudely dip molded sides and the "free-blown" shoulder.  This bottle does not show much of a texture difference between the mold formed sides and the free-blown shoulders.  The distinct taper to these type bottles helped facilitate removal from the mold. 

(Note: Sometimes European made case gin bottles will have distinct vertical lines on the four sides which were mold induced.  On dip molded bottles this may possibly be from rubbing as the bottle was withdrawn from the mold [Shafer 1969].  These type gins - both dip and conventionally molded - are occasionally called "shingle mold" gins by collectors since the lines resemble shingle texture.  Not far fetched as it is believed that some early square molds were formed by four wooden boards nailed together [Jones & Sullivan 1989].  As noted earlier, wooden molds had to be kept very wet in order to survive for long with the 2000+ degree heat of molten glass.  Steam formed at the interface between the wet wooden mold and the hot glass [Deiss pers. comm. 2005].  It has also been speculated that this body texture feature may have been caused by the use of wooden paddles or a block to form the body - at least in the early 18th century [Boow 1991].)

Another example of a dip molded American made bottle is the deep golden amber bottle to the left.  This is an early "snuff" (powdered tobacco) bottle that likely dates from the first third of the 19th century.  This was blown in a more elaborate square dip mold which molded the four flat sides and formed the beveled corners.  The shoulders are free-blown and the flared finish tooled to shape; the base has a glass-tipped pontil scar.  There is no evidence of mold seams on this bottle though it has the glossy appearance of a fire polished bottle.  The body of the bottle has some texture to it which contrasts with the smooth glossy sheen of the free-blown shoulders (Jones 1986).  (Note: Early American bottles in this color are often attributed to glassworks operating in the Stoddard, NH. area, though similar items in similar colors were made by many glass manufacturers along the eastern seaboard.)

Dating notes:  Dip molded bottles were produced during (and before) the earliest part of the era covered by this website, being used at least as early as the early 1700s for bottles.  The most common date range for English dip molded bottles is from the 1730s to 1820s, when the three-piece Rickett's mold came into widespread use.  From the 1820s on dip molded bottles were gradually displaced by full-sized molds to virtual disappearance around 1865 to 1870 (Jones 1986; Boow 1991).  It is likely that American made products roughly followed these same time lines with an end date maybe as late as the early 1870s (Wilson & Wilson 1968). 

Be aware that dip mold produced bottles will often be mistaken for turn-molded bottles and vice versa.  The key to differentiation is that a turn-mold bottle will almost always have numerous, perfectly horizontal though faint striations on the glass surface in many places on the body, shoulder and neck; no pontil scarred examples of a turn-mold have ever been noted by the author.  A dip molded bottle will usually have a horizontal line or glass discontinuity at the should interface or break between the upper body and lower shoulder, but will not have multiple, perfectly horizontal lines anywhere else on the bottle body, shoulder, or neck.

Jones (1986) noted that, "The dip mold was in use for such a long period and its use is frequently so difficult to identify that it is virtually useless as a dating tool."  Though largely true, when dip mold manufacturing features are identifiable there is some dating utility.  In Western America, the earlier gold rush era sites (1850-1870) are often indicated by the presence of dip molded bottles.  In general, dip molded bottles are commonly found on historic sites dating from the Civil War and before, but very rarely on sites dating after that time.  (Note: One of the better reference sources on dip molded bottles is Olive Jones 1986 book entitled Cylindrical English Wine & Beer Bottles 1735-1850.)
 

Pattern mold/half-post methods

Pattern molds:  Any bottle mold can have a pattern (or lettering) inscribed or cut into its surface.  As used on this website the term "pattern mold" is a variation of the dip mold in which a pattern was inscribed on the inside surface of the mold.  With bottles the pattern was typically vertical lines or ribs which resulted in a distinct ribbed pattern on the glass surface.  This gave rise the alternative name "rib mold."  Some molds had diamond (cross-hatched) or spiral rib patterns engraved on the surface; these molds would have been two piece molds which could open to facilitate removal of the parison (McKearin & Wilson 1978).  The "Pitkin" style flask pictured to the left was produced in a pattern mold and actually patterned twice during the "half-post" blowing operation (covered below).  Pattern molding was more common with glassware, but was used frequently to produce bottles during the first half of the 19th century (Jones & Sullivan 1989).

Pattern molds were smaller than the finished bottle (i.e. not a "full sized mold") since the mold was used primarily to impress a pattern on the glass surface, not to completely form the bottle base, body, shoulder, and/or neck.  Once patterned, the bottle was removed from the mold and blown, expanded, and manipulated with tools in order to achieve the desired shape and size (Munsey 1970).  The pattern on finished bottles is a series of variably subtle indentations and intervening humps which are typically more distinct towards the shoulder than towards the base.  Pattern molded bottles will usually have the mold induced pattern covering the body and continuing from the sides "seamlessly"  around the heel and onto the base (Kendrick 1968).  Click pattern mold base to view a picture showing the pattern continuing on to the base of the bottle pictured to the left.

Since the bottle is only patterned and not completed formed by the mold, pattern molded bottles are really a variation of a free-blown method described elsewhere on this website.   Because of the post-patterning blowing of these type bottles, the adjective "expanded" is often used to describe these bottles, i.e. "expanded vertical ribbing" like the flask pictured to the right.  Many or most pattern molded bottles had one pattern impressed on them from one "dip" in the patterned mold.  A feature of pattern molded bottles is that the ribs are expanded (wider) on the body of the bottle and drawn together at the shoulder/neck and base - a function of the post pattern molding expansion.  Many pattern molded bottles have ribs that are swirled one direction or the other.  This was caused by twisting the bottle on the blowpipe while expanding (McKearin & Wilson 1978).  Both of the flasks pictured to the left (above and below) have swirled ribs indicating being twisted while blown.

The bottle pictured to the right is an early American (late 18th to early 19th century) "nursing" bottle that was patterned once with a mold that had 19 engraved vertical ridges.  This pattern would be referred to as having "19 vertical ribs."   Click nursing bottle side view to see a close up of the side of this bottle showing the ribs somewhat more distinctly.  This flask also has a glass-tipped pontil scar on the base.  Whether these relatively common (for the period produced) long flattened ovoid shaped flasks were used as nursing bottles is not known for sure, though that is what they are commonly referred to by collectors.  They well could have been used for liquor or a host of other liquid products (McKearin & Wilson 1978; Jones & Smith 1985).

Half-post method:  A variation on the dip mold/pattern mold theme is a method of bottle production where the gather is slightly expanded then dipped again into the glass pot to apply a second layer of glass over the initial gather.  This second layer of glass typically covered the base and body portions of the first gather ending on the upper shoulder.  Postes was a French term for a gather of molten glass.  Thus the term "half-post" for this method, though these bottles are well more that "half" covered by the second coating of glass (McKearin & Wilson 1978).  The end point for this second layer of glass is indicated by a thickened ridge on the upper shoulder of the finished bottle.   Click Pitkin shoulder to see a close-up picture of this ridge which shows just below the bottom of the neck and just above the pattern mold ridges.  (This close-up is of the olive green flask pictured to the left.)

This method was used with regular shoulder height dip molds of various shapes and with pattern molds.  Bottles produced by this method are often called "double-dipped" in collector jargon.   Some early collectors incorrectly believed that the neck of these type bottles were "inserted" into the body of the bottle, a largely impossible feat.  The term "inserted neck" still crops up occasionally however (McKearin & Wilson 1978).  This production method is also often referred to as the "German half-post" method since it was believed to have originated in Germany (Munsey 1970). 

Certain types of half-post produced bottles - like the "Pitkin" style flasks - were pattern molded after the application of the second layer of glass.  The flask could be patterned once (like the nursing bottle pictured above right) or patterned twice giving a "broken swirl" appearance to the bottle, which can often resemble popcorn kernels.  The forest green Pitkin style flask pictured to the above left is of early American origin and produced by the half-post method; note the horizontal ridge encircling the shoulder just below the neck.  This flask is single patterned on the upper 40% of the body and double patterned on the lower 60% (click picture to enlarge).  It was most likely made at a New England glassworks between 1780 and 1820 and would be referred as being "swirled to the right" (from the bottom of the body upwards) which is the most common direction for swirling on New England "Pitkins" (McKearin & Wilson 1978; Noordsy 2003).   The light green "Pitkin" style flask pictured above at the beginning of this section is another example of a double patterned "broken swirl" flask from the same era.  This is an unusual color for a New England style "Pitkin" as most were blown in darker shades of green and sometimes amber (e.g., olive green, olive amber) (Noordsy 2003).

Not all Pitkin style flasks were made by the New England glass factories.  Many were made by various glassworks further to the west.  The Pitkin style flask to the right was most likely produced at a Midwestern glass factory - Ohio or possibly western Pennsylvania (Pittsburgh) - during the first third of the 19th century.  It's heritage is indicated by the brighter green color and the more circular shape of the bottle body.  This flask was also twice pattern molded resulting in the "broken swirl" pattern (McKearin & Wilson 1978).  Click Midwestern Pitkin close-up to view a close-up of this flask which distinctly shows the half-post "ridge" on the upper shoulder as well as the pattern mold ridges.  This flask would be referred to as being "swirled to the left."  Midwestern flasks were rarely if ever blown in olive-green or olive-amber and are most common in more vibrant greens, shades of amber, and aqua.

Dating notes:   Pattern molded bottles are some of the earliest American bottles.  American made pattern molded bottles and flasks like those discussed here would not likely date after the 1840s and typically would date from the 1780s into the 1830s.  New England "Pitkin" flasks are believed to date between 1780 and the 1820s; the Midwestern "Pitkins" date from about 1800 to 1835 (McKearin & Wilson 1978).  Because of the early production of these type bottles, pattern molded bottles and flasks are rarely found on historic sites in the West, but would be commonly encountered in the East and Midwest. 

(If not already obvious, the best discussion of pattern molds and molding, as well as the differences between New England and Midwestern Pitkins is found in McKearin & Wilson's (1978) classic book American Bottles and Flasks and Their Ancestry - pages 322-333.  See the References page.)
 

Molded shape related features

Full sized bottle molds could be made to create just about any body shape for a bottle that could be imagined including animals, human figures, vegetables, purely decorative designs, as well as a myriad of more mundane and purely functional shapes.  The photo to the left shows a variety of molded body shapes that does not even begin to represent the variety found in bottles made during the era covered by this website - the 1800s to mid 20th century.  (Two illustrations of full sized molds are shown in this section below.)

Molds were created to produce either standard shaped bottles that were used by various purchasers wanting standard, product identifiable shapes or were custom made to reflect the specific desires of a bottle buyer.  Individual molds were produced by custom mold shops or, at larger glass companies, by the company itself in on site machine shops.  Relative to the latter point regarding custom made molds, the following is quoted from the Illinois Glass Company's 1906 Illustrated Catalogue and Price List:

Moulds for Special Shapes - Many Bottle users prefer shapes and designs of their own.  For all such we are thoroughly equipped in our own extensive Machine Shop to make at short notice moulds for any practicable bottle, and at the lowest possible cost for first-class work.  In ordering a special shape, an exact model of same should be furnished.  In cases where this is impracticable, our own artist will produce a wooden model of the desired bottle if furnished with the idea by a drawing or otherwise.  If we make the moulds no expense will attach for models; otherwise a charge for the actual cost of producing same will be necessary.  Special Moulds should always be made in pairs for each size and shape, for economy's sake.  Where large quantities of bottles are desired this is indispensable. Better and more uniform bottles are always secured when moulds are worked in pairs.  The cut herewith shows a mould for an oval prescription bottle.  The mould is made of the best grade of gray iron, and weighs about 80 lbs. 

The noted mold illustration (i.e. "cut") from the 1906 catalog is shown to the above right (Illinois Glass Company 1906).  This illustration shows a very typical side-hinged mold conformation for a mouth-blown bottle that appears to be a cup-mold which dominated mold types by the early 20th century.  The skills needed to form a bottle with a mold - though considerable - were less than the skills needed to form a bottle free-blown.  Even a master glassblower (gaffer) was limited in what could be produced free-blown as the shapes were limited by the techniques that could done via the glassblower lungs, movement of the blowpipe, use of a marver (a flat surface) and block (hollowed out surface), and other hand tools (Kendrick 1968).  Click molding a mouth-blown bottle to see an illustration of a bottle being blown in a two-piece mold.

The use of full sized molds also allowed for a dramatic increase in the speed of production.  Free blowing likely only allowed for a production of a few hundred bottles per day (likely 12-14 hour days) per glassblower, who was assisted by at least one other person - the servitor.  Dip molding probably increased this production significantly, but still was low production compared to later eras (McKearin & Wilson 1978).  Tooley noted the following 24 hour production amounts between shops using hand production using a mold - 45-105 gross taking 6-7 people to produce - and modern (1953) machine production of 250-1500 gross with one person running the machine.  These ranges covered bottles from 3 to 32 oz. in size, with larger bottles taking more time than smaller ones (Tooley 1953).

The body, shoulder, and or neck of a bottle can be molded into a variety of shapes.  A common molding feature is the paneled body.  Panels are generally flat indentations into the body formed by the mold and usually perpendicular to the base.  Click Hall's Balsam for the Lungs to view a picture of two bottle which have sunken or indented panels on all four sides of the bottle.  Panels can come in all types of shapes including arched or gothic (like large blue-aqua pickle bottle in the group picture above), chamfered (like the Hall's Balsam bottles), tapered, rectangular, round, square, and others (Berge 1980).

Bottle shapes during the mouth-blown era were incredibly varied and done for a variety of reasons (no particular order):

▪Product or content identification - use of an accepted shape for a given product type;
▪For brand identification - use of special shapes to identify a specific proprietary product like the H. H. Warner Company's Tippecanoe (a proprietary medicine) pictured to the left;
▪As a warning  - use of special shapes or embossing in order to warn the consumer that the contents were poisonous;
▪Functionality - certain shapes or designs were necessary for certain products because of carbonation or other physical attributes;
▪Decorative reasons - to attract potential purchasers;
▪Vanity of the bottle buying customer;
▪...and likely a lot of other reasons.

The illustration and photo to the above right shows a ca. 1870-1880 full sized post-mold for a "Saratoga" style mineral water bottle and an emerald green mineral water bottle that was produced in a similar mold.  The subject of molded bottle shapes is more comprehensively covered on the Bottle Typing/Diagnostic Shapes page since form follows function to a large degree with historic bottles.  The "Bottle Typing/Diagnostic Shapes" page makes an attempt at classifying bottles by diagnostic - and typically molded - shapes, so the subject is not pursued further here.

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Mold seams

General Information:  With the exception of one-piece dip molds and turn-mold bottles (covered later), all bottle molds potentially leave evidence of the joints where the mold pieces came together, i.e. mold seams where were also know in the industry as "joint-marks" (Scholes 1952).  Mold seams can be virtually impossible to see on bottles where the parts of the mold fit together very tightly (unusual even with modern machine molds) or the body of the bottle received post-molding fire polishing which usually erases the evidence of mold seams.  On this website the term "mold seam" is used to refer to the seams on the bottle where two parts came together and the interface or joints between mold sections that result in the bottle seams, depending on context.  Fortunately, on a large majority of full sized mold blown bottles all or a major portion of the side mold seams are quite evident. 

Bottles blown in loose fitting molds can result in glass being forced or extruded into the mold seams.  This is evidenced on a bottle by distinctly thickened mold seams or mold seams that project distinctly outward from the body of the bottle.  Extreme examples of these glass extrusions usually broke off with handling leaving a rough edge to the mold seam.  This feature is observed typically near the base on the lower sides of a bottle or at the junction area between the shoulder and neck.  Bottles with this feature are virtually always mouth-blown and not machine-made.  The picture to the right shows this mold seam feature at the junction of the neck and shoulder on a ca. 1870 liquor flask made by (and embossed as such) CUNNIGNHAMS & IHMSEN GLASSMAKERS, PITTSBURGH, PA.   Click link to view a picture of the entire flask.  The pictured example has some of extrusion glass remaining with the remainder (gap between flap of glass and shoulder) having been broken off at some time in the past - possibly when removing the bottle from the mold. The author of this site has never seen a machine-made bottle with this feature, though such could theoretically exist since all molds have seam joints.  However, a person could be quite confident that a bottle fragment with this feature would surely be from a mouth-blown bottle.

The portion of a bottle where it is usually the easiest to observe mold seams is on the shoulder and lower portion of the neck.  On round (in cross section) bottles, the body is also usually an easy place to observe the seams.  On non-round bottles (e.g., square, rectangular, hexagonal, etc.) the body side mold seam is often concealed by the mold formed corners where two sides meet.  As a general rule (with exceptions of course as with virtually all bottle diagnostic features) mouth-blown bottles will have more distinct (thicker, higher) body mold seams than machine-made bottles, which tend to have very fine (hair thin, little protuberance) mold lines as well as other attributes covered later.  The following discussion just covers mouth-blown bottles; machine-made bottles are covered later on this page.

Note: One of the best sources for information on mold seams is in Dr. Julian Toulouse's often cited two-part article entitled "A Primer on Mold Seams" in the November and December 1969 editions of the long defunct magazine The Western Collector (Toulouse 1969b).  Faster loading "jpg" scans of this milestone work are available by clicking on the following links - 2 magazine pages per scan, 20 magazine pages in total.  The page numbers listed here coincide with the pages of the original articles.  (Articles reproduced courtesy of Dr. Cecil Munsey.)
Part I -   pages 526-527, pages 528-529, pages 530-531, pages 532-533, pages 534-535.
Part II - pages 578-579, pages 580-581, pages 582-583, pages 584-585, pages 586-587.

A better quality version of the entire article, which is more suitable for printing, is available by clicking on the following link:  " Primer on Mold Seams"  - Parts I & II   This file (pdf) is viewable in Adobe Acrobat Reader.

Mouth-blown bottle body mold seams

Two-piece mold body seams:  Two-piece molded bottles have 2 opposite body mold seams running from the heel of the bottle to a termination point somewhere on the upper neck or finish.  Two-piece molds are by far the most common orientation of molds, though these molds typically were made of at least three separate pieces when one includes the base plate.  Plates for embossing were also commonly incorporated into two-piece molds giving at least four sections to the mold.  However, the pervasive use of the term "two-piece" mold for all bottles with two mold seams on opposite sides of the bottle is not going to change even though it is semantically incorrect (Toulouse 1969b).  Due to the universal use, we continue that convention on this website.

The body or side mold seams formed by a hinge/key mold, post mold, or cup mold are indistinguishable from each other without looking at the base of the bottle.  The figured flask base pictured to the right is a true two-piece hinge mold as there was no separate base plate - each half of the base was included with that half of the body mold.  As there are no unique diagnostic features associated with the fact that a bottle body has two opposing mold seams, the user is directed to review the discussion of the varying related base mold markings on the Bottle Bases page.  Specifically, click keyed & hinged mold to view the discussion of the different true two-piece molds; click post mold to view the discussion of that type of "two-piece" mold; and click cup mold to view the discussion of that type of "two-piece" mold.   For a discussion about where the mold seam ends on the neck/finish of a bottle and what it means, view the applied and tooled finish portion of the Bottle Finishes & Closures page.

Three-piece mold body seams:  In conjunction with the true two-piece mold, one of the earliest mold types to be used in the U.S. was the "three-piece mold" which was likely first used in about 1814, patented by the Henry Ricketts (Bristol, England) in 1821 or 1822, and likely adapted into the U.S. by the 1830s (McKearin & Wilson 1978; Hume 1991).  Although earlier versions of a three-piece mold may pre-date the Rickett's mold it is not certain.  If so, they would have been essentially a dip mold with two shoulder mold sections added.  Rickett's patent added several other features, including hinged shoulder parts and foot controls for opening and closing the mold, both of which were significant improvements in efficiency (Jones 1986).  The Rickett's mold also consisted of at least four parts - two opposing shoulder parts, dip mold body portion, and a moveable base plate which could be changed to achieve different base configurations or for different embossing.  This was likely the first plate mold (McKearin & Wilson 1978, Jones 1983).  Most true Rickett's produced bottles are embossed on the base with H. RICKETT'S & CO. GLASS WORKS BRISTOL, date between 1821 and the 1850s, and usually have a sand pontil scar.

Morphologically, typical three-piece mold bottles have a horizontal mold seam encircling the bottle where the shoulder and body meet and two mold seams on opposite sides running vertically from the shoulder seam, up the shoulder, and variably up the neck and/or finish.  Click on the picture of a light amethyst liquor bottle below to view a close-up of the very distinct mold seams on the shoulder and neck of this later mouth-blown, three-piece mold liquor bottle dating from the early 20th century (1900-1910).  Consider the location of the mold seams in the picture with the conformation of the three-piece mold in the illustration above.  Three-piece mold liquor bottles were a popular style and manufacturing method into the early 20th century and are shown in catalogs dating until at least 1908 (Illinois Glass Co. 1908).

The vertical body side seams on earlier (1821 to about 1840) three-piece mold bottles disappear right at the junction of the shoulder and neck (Jones 1986).  This is typical of the early Ricketts' bottles which were not molded above this point; the neck instead being formed by glassblower manipulation.  The olive green bottle pictured to the right is an early sand pontiled Ricketts' liquor bottle which is blob sealed and dated (1822).  This bottle is also embossed H. RICKETT'S & CO. GLASS WORKS BRISTOL on the base and PATENT on the shoulder.  The horizontal shoulder seam is faint but in evidence as well as the vertical shoulder seams, which both terminate right at the neck-shoulder junction indicating that the neck and finish were both hand formed.  It should be noted that similar (though usually a bit taller and smaller in diameter) three-piece molded cylindrical bottles with PATENT embossed on the shoulder were widely made and used for spirits in the U. S. from the 1830s to 1870s.  Click Tall, moderately slender bodied, straight neck "Patent" style spirits cylinder (mid-19th century) for more information on these bottles.

Later vertical side mold seams end immediately below the base of the applied finish (about 1840 through the 1880s). The latest three-piece mold bottles (1890s into the 1910s) have tooled finishes with the vertical side mold seams ending on the upper portion of the neck or in the finish itself, i.e. end just beyond where the lipping tool ended.  The liquor bottle pictured to the left has the side mold seams ending within the finish if one looks closely.  Three-piece mold bottles are not embossed on the body of the bottle, though as noted above may have embossing on the shoulder (common), neck (unusual), and/or base (also common).

Most bottles which are commonly referred to as three-piece molds were actually made in a mold that had a fourth base plate piece, like noted above for the Rickett's bottles.  Use of a separate base piece probably made construction of the mold easier.  Although most three-piece mold bottles actually had four mold parts, referring to them as "three-piece" molds will continue due to its ubiquitous use over the years, similar to the two-piece mold discussed earlier.  To suggest changing the name would be confusing and unproductive since most people understand what is being referred to (Toulouse 1969b).  The four-piece mold is a variation of the three-piece mold with two body halves instead of one; this mold type is discussed in the box below.

An unusual, though minor, variation of the standard three-piece mold conformation is as discussed and pictured at the following link:  http://www.bottlemysteries.com/2008/08/bottle-mystery-key-lock-on-a-shoulder-seam-bottle-mark/  This three-piece mold style included small locking flange points where the two upper halves connected or "locked" with the lower "dip" portion of the mold.  This is evidenced by the squared off mold seam discontinuity that disrupts the horizontal shoulder seam on each side of these bottles - one in the middle of each of the two upper mold parts - with a corresponding "lock" portion on the immediately opposing upper surface of the lower mold part.  These type bottles are rarely encountered and seem to date only from the pre-Civil War period, i.e., 1830-1860.  See the image and discussion at the above link for more information.

Three part mold with three body-mold leaves:  This mold type is a distinct variation of the above described three-piece mold with a very different orientation to the mold portions.  Instead of the single body mold and split (two-part) shoulder/neck molds like described for the typical three-piece mold bottle, this three-piece mold is composed of three more or less equal sized pieces that fit together along vertical seams, i.e. three equal mold "leaves' that produce a bottle that has three vertical mold seams from heel to upper neck or finish.  One of the mold pieces was typically attached permanently to the base plate, with the other two hinged so that they could open to insert a gather and to extract the blown item.  The base can be either of a 'post' or 'cup' design (McKearin & McKearin 1941; Toulouse 1969b).  This type mold is referred to as a three-piece "leaf" mold on this website.

This early method of molding was used primarily to produce what is termed "blown three mold glass" and other highly decorative type bottles.  A benefit of this mold conformation was the ability to engrave much more elaborate designs than could be produced with conventional two-piece molds; designs that covered the entire bottle right up to the mold seams (McKearin & McKearin 1941; Toulouse 1969b).  A typical example of an item produced in a three-piece "leaf" mold is the late 19th century salt shaker pictured above right.  This is 1896 pattern was called the "Imperial" (also known by collectors as the "Jeweled Moon & Star" pattern) by the producer - the Co-operative Flint Glass Co. of Beaver Falls, PA. (Dori Miles, pattern glass expert pers. comm. 2008 - www.eapgpatterns.com).  (Note: Although the glassmaker name included Flint Glass Co. this item is not true flint glass, but instead colorless glass made that way with the addition of manganese dioxide in the batch.  See the colorless glass discussion on the Bottle/Glass Colors page for more information.)  The pictured item has three vertical mold seams from the heel to the roughly cracked-off lip surface, and a cup mold base.  One vertical seam can be seen in the middle of the bottle; the other two vertical seams are not visible but in the vicinity of where the lines point to in the picture.  As this picture shows, the mold engraved pattern is quite elaborate and integrates well around the mold seams.  (Note: Some highly decorative "specialty" bottles (e.g., salt shakers, perfume, cruets) were occasionally made with four mold "leaves" resulting in four sides seams; more parts are conceptual possible but have not be noted by the author of this website.)

The heavily embossed bottle pictured to the above left is a much earlier three-piece 'leaf' molded bottle or decanter.  This early American bottle was produced by the Keene Marlboro Street Factory, Keene, NH. in the 1820s or 1830s and is classified as GIII-16 by McKearin & McKearin (1941).  The three vertical mold seams on this bottle are well disguised by the elaborate body pattern and are only obvious where a horizontal or diagonal line intersects the mold seam.  The side mold seams end just below the constricted area just below the flared finish.

Dating notes:  Since typical three-piece mold bottles were made for close to a century (1821 through the 1910s) other diagnostic features unrelated to the body seams must usually be used.  One exception, as noted above, is that the earliest three-piece mold bottles (1821 to about 1840) will have the vertical side mold seams ending at the base of the neck since the neck was not molded (Jones 1986).  The vast majority of these earlier three-piece mold bottles are olive green, olive amber, black glass, or similar colors.  Three-part "leaf" molded bottles can date from as early as the 1820s into the early portions of the 20th century, ending as mouth-blown manufacture disappeared.  Specific bottle dating would have to use a variety of other diagnostic features to narrow the manufacturing date range.

For additional information, see the discussion of three-piece molds on the Bottle Bases page.  Also, click on  pages 578-579, pages 580-581 to view the section of Toulouse's 1969 article 'A Primer on Mold Seams' that deals with both types of three-piece mold formed bottles.

Notes on four-piece molds:  The term four-piece mold refers to a mold that has four main body parts - two for the shoulder and neck (and sometimes extreme upper body) and two for the majority (or all) of the body.  Four-piece molded bottles are very similar to the three-piece molded bottles in that there is a horizontal seam on or just below the shoulder with the side mold seams running vertically up the shoulder and neck from this horizontal seam.  However, four-piece mold bottles also have vertical body side mold seams which run down from the shoulder seam to at least the heel of the bottle.  The picture to the left shows these shoulder/body seams.  Click star base liquor bottle to see a picture of this entire bottle which dates from the late 1870s to mid 1880s (applied finish, no air venting). Virtually all four-piece molds also had a fifth base plate portion which could have the conformation of either a "post" or a "cup."  Review the descriptions for the post mold and cup mold bases on the