Glassmaking & Glassmakers

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INTRODUCTION

The following is quoted from Munsey (1970): 

"Knowing the techniques of glassblowing, including how to identify bottles made by hand, either free-blown or mold-blown, and by automatic methods, is a valuable help in dating bottles."

The purpose of this page is do just what Dr. Munsey notes - describe the different basic techniques used in producing bottles during the time period covered by this website, i.e., the 19th through mid 20th centuries.  Simply stated, an understanding of how bottle making processes worked enhances ones understanding and ability to identify the different manufacturing based diagnostic features that are discussed and used on this website to date bottles. This begins with the era of mouth-blown bottles - a process depicted in the late 19th-century trade card pictured above - through the conquest of the bottle manufacturing world by fully automatic bottle making machines during the first few decades of the 20th century.  This page is not intended to be a complete history or overview of the glassmaking in America and in fact, does not specifically cover the actual glass making process at all.  Instead, it attempts to cover the basic bottle making processes that are pertinent to the goals of this website as stated on the Homepage, with some anecdotes and related information here and there for interest and illumination.  (The subject of the history of glassmaking in America is well covered by a couple out-of-print, but widely available used books: American Glass (McKearin & McKearin 1941) and American Bottles and Flasks and Their Ancestry (McKearin & Wilson 1978).)

The era from the third quarter of the 19th century through the first quarter of the 20th century was a time when change was rampant within the bottle making industry (Barnett 1926).  Up until the mid-19th century, bottle and glass making followed virtually the same craft-based processes that had been used for many centuries.  Bottles made in the 1630s (or even the 1030s for that matter) were made in an virtually identical fashion to many bottles made in the 1830s, with some stylistic shape differences of course. 

For example, the American made free-blown bottle pictured to the left which is commonly called a "New England chestnut" could, from purely a manufacturing technique perspective, have been blown in Europe several hundred years earlier - or in ancient Rome two thousand years ago (bottle to the right ca. 100 A. D.) - than its likely production date between 1790 and 1820 (Scoville 1948; McKearin & Wilson 1978; Cable 1999; Griffenhagen & Bogard 1999; Van den Bossche 2001).  (This "chestnut" bottle is described further on the Examples of Dating Historic Bottles page.)  Although the shapes are different, both pictured bottles were produced with identical methods - free-blown, pontil scarred, with applied finishes.

After automation dominated the bottle making industry during the first quarter of the 20th century, change as evidenced by the manufacturing related diagnostic features physically apparent on a bottle was also limited.  For example, a 12 oz. crown finish, micro-brew beer bottle produced today shares virtually the same manufacturing induced physical features-  including the location of mold seams - as a beer bottle produced by an early machine in 1918.  The same is true of all types of bottles, although styles (shapes) have changed somewhat over that time depending on the use of the bottle.  (Note: Undoubtedly, there have been major behind the scenes advances in machine efficiency and design, but these changes are little reflected in the physical features found on most bottles with the exception that more modern bottles (World War II and later) tend to be of thinner glass than earlier machine-made bottles. The primary change during the last third of the 20th century has been the displacement of glass in favor of plastic containers.)

To describe this a different way picture in your mind a bell curve graph with the amount of technological change in the bottle making industry as evidenced by the physical appearance of the bottle on the left vertical axis (change increasing upwards) and time on the lower horizontal axis beginning with 1750 on the left moving right to 2006.  Most of the "bell" would lie in the area between 1840 and 1920 with the peak of the bell most likely being around 1905-1910 when the widespread licensing of the Owens Automatic Bottle Machine began.  Before 1840 (and to a large degree before 1870) and after 1920, the lines would be relatively flat and very low on the "change" axis.  The point here is that bottles made before the mid-19th century and those made after about 1920 share very similar manufacturing induced physical features with other bottles within those respective age groups (Scoville 1948; McKearin & Wilson 1978; Van den Bossche 2001).

One additional subject is also briefly covered via this webpage: bottle/glass makers markings.  The subject of bottle/glass makers is important because the embossed markings that bottle makers placed on their wares, if present, are often excellent tools to assist a person in narrowing down a date range that a particular bottle was most likely produced, when used along with the manufacturing based diagnostic features.  This subject is explored in Part C. Bottle & Glass Makers Marks at the bottom of this page, though most of the information is found on a separate webpage at the following link: Bottle & Glass Makers Markings page. 
 

A. Mouth-blown Manufacturing

Free-Blown Manufacturing 

The earliest utilitarian bottles made in the U.S. were almost certainly free-blown.  Free-blown bottles were produced without the aid of a containment mold being instead formed and shaped by the skills of the glassblower using manipulation of the blowpipe, various simple hand tools, and usually a hollowed out block and a flat table called a marver.  Free-blown utilitarian bottles found or made in the U.S. typically date from or before the American Civil War (early 1860s and prior) and can be, of course, much older than that.  They were rarely produced after the 1860s by American glass companies producing utilitarian bottles though the technique is still being used to some degree for specialty or artistic bottles (Toulouse 1969a; empirical observations).

The following excerpt is from Munsey (1970) and is a very good overview of the relatively complicated and skill intensive glassblowing process.  It also pertains to mouth-blown molded bottles with the addition of the molding process instead of the extensive hand manipulation noted.   (Molded bottles are covered in the next section.)  See the Glossary page for a description of some of the glassmaker jargon noted (e.g., gaffer, battledore, chair):

Hand-blown bottles can be either free-blown or mold-blown.  Taking a warmed blowpipe, several feet in length, the gaffer's assistant, the gatherer, inserts its tip through the bocca into the hot glass and turns it until a sufficient amount of glass has accumulated on the blowpipe.  (Authors note: The late 19th century European trade card below shows glassworkers making gathers via the bocca - or opening - in the glass furnace.)  The gatherer then passes the blowpipe with the gather (hot glass on the tip of the blowpipe), sometimes called the post, to the servitor, who is the master blower's first assistant; the servitor then rolls the gather on a marble or metal slab called a marver.  (Click marvering to view an illustration of this process.) This action gives the gather its basic bottle shape.  The servitor then passes the blowpipe to the gaffer.  If the bottle is to be hand-blown, the gaffer constantly rotates the gather to keep it from drooping while he makes the initial blow which introduces an air pocket into the gather.  From this point the gather is called a parison.  The parison is then rolled in a block (a wooden dipper-like device cut out on one side) which forces the glass into the shape of a sphere; he also blows at the same time to increase the size of the parison.  The block is kept from burning by an occasional splashing with water; the relatively cool block also cools the glass surface which helps retain the desired shape.

At this point the servitor puts the parison back in the furnace for reheating (by the mid-1800s he used a smaller and hotter furnace called the glory hole) and then returns it to the gaffer.  Through various manipulations and continued blowing the gaffer completes the shape of the bottle.  Spinning the blowpipe rounds the parison out like a ball, providing the basic shape of globular bottles.  By swinging the blowpipe back and forth or in a complete circle the parison is elongated, providing the basic shape of long cylindrical bottles.  Square free-blown bottles are obtained by slapping the parison on the marver and/or paddling it with a wooden paddle called a battledore.  To make the bottom of the bottle flat, the gaffer may bang the plastic parison on the marver.

To take the final steps necessary in forming a free-blown bottle the gaffer sits at a workbench called a chair.  The blowpipe is placed across the arms of the chair, which are tilted downward away from the gaffer, and is gently rotated during the completion period.  The most important tool the gaffer uses at this stage is the pucellas, a tong-like instrument more often called a tool.  (Click chair use to view an illustration of these processes.)  As the blowpipe is rotated the tool is sometimes used to narrow the neck of the bottle in preparation for finishing (completing the neck and mouth).  Shears resembling tin snips are sometimes used to cut the plastic metal - for example, glass to be made into handles.  At this stage the bottle is ready for the final manipulations of finishing...

Before either a free-blown or mold-blown bottle can be removed from the blowpipe some arrangement must be made to hold it during the finishing of the neck and lip.  The holding process is properly called empontilling.  Until around the mid-1800s the prevalent method was to take a separate rod or blowpipe tipped with hot glass and stick it to the bottom of the bottle.  With the pontil holding the bottle, the blowpipe used for the development of the bottle could be removed to allow finishing...  (Click empontilling and cracking off to see an illustration of these processes.)

By far the best, and as a result the most popular, method of severing the blowpipe from the bottle is a process known as wetting off.  Wetting off is merely marking with a wet wooden paddle around the neck of the hot bottle where it is attached to the blowpipe.  The cold water weakens the glass in the desired spot and a sharp tap by the gaffer breaks the bottle free from the blowpipe.  Another popular method of severing the blowpipe from the bottle is by cutting the neck with shears... (Munsey 1970)

At this point in the glassblowing process the bottle is now "finished", which is usually the application and/or manipulation of glass at the bore/throat of the bottle to form a lip and/or collar of some type.  Finishing and many related issues, including wetting or cracking-off (an example pictured to the right on a mold-blown bottle), are covered in depth on the main Bottle Finishes & Closures page and will not be extensively covered here.   The primary physical characteristics of a free-blown bottle are found on the Bottle Body Characteristics & Mold Seams page. 

One of the better books covering the process of blowing bottles and glass, with scores of pictures, was Grace Kendrick's (1968) "The Mouth-Blown Bottle."  For an in-depth coverage of all aspects of glassmaking, including glass mixing, annealing, tools, furnaces, and glassblowing see Frank Kulasiewicz's (1974) "Glassblowing" which is an excellent source of information.

Empontilling & Snap Cases

Empontilling:  A pontil mark is a variable size and type of scar left on the base of a bottle by a pontil rod.  A typical pontil rod or "punte" was a long (4-6 feet) rod which was securely attached to the base of the just blown hot bottle.  The rod had to be long enough so that the heat transference from the extremely hot (2000°+ F.) bottle did not reach the hands of the pontil rod holder.  A pontil rod held the bottle during the steps in the bottle blowing process where the blowpipe is removed (cracked-off) from the bottle and that break-off point is "finished", i.e., the lip or finish is completed.  Once the bottle is "finished", the pontil rod is sharply tapped which breaks it free of the bottle.  The base of a bottle which was held with a pontil rod will almost always retain some evidence of the pontil rod attachment.

Pontil rods and the resultant pontil scars go back to antiquity, having been used for bottle making as early as Roman times (McKearin 1941).  All of the different pontil scars noted below are usually (but not exclusively) found on American made utilitarian bottles that date to or before the American Civil War (mid-1860s).  Pontil scars of all types became ever increasingly unusual on utilitarian bottles as the 1860s progressed and largely disappeared by the late 1860s or early 1870s as various "snap" or snap case tools dominated the task of grasping the hot bottle for finishing (the snap case is covered later on this page).  However, the transition time for conversion from the pontil rod to the snap case was lengthy.  The first use of the tool in the United States may have been in the 1840s, but its use was definitely evident by at least the early 1850s.  Thus, utilitarian bottles without a pontil scar can date as early as the late 1840s to early 1850s (though rarely earlier) and pontil scars can be found infrequently on bottles made in the late 1860s and early 1870s (Toulouse 1968; Newman 1970; Munsey 1970; Watson & Skrill 1971; Jones 1986; Jones & Sullivan 1989; McDougall 1990; Van den Bossche 2001).

Glass tipped Pontil:  This type pontil scar was formed by the use of a solid iron bar as the pontil rod.  One slightly widened end of the bar was tipped with molten glass then applied and fused to the base of the bottle.  A glass tipped pontil rod made contact with most or all of the bottle base within the confines of the diameter of the pontil rod tip.   Click HERE to view an illustration of a glass tipped pontil in action.

When the rod was broken free of the bottle, a generally round but fragmented scar was left behind on the base of the bottle.  This is usually manifested primarily by an assortment of glass fragments protruding above the base of the bottle.  In addition, the rod would usually take with it some small glass fragments from the base of the bottle leaving a scar which is a round scattering of "bumps and gouges" without a distinctly unmarred center - like the blowpipe pontil scar described below.   Click on the picture to the left to see an enlarged version of a typical glass-tipped pontil scar that shows the detail better.  (Click sauce bottle to view a picture of the entire bottle.)   The glass tipped pontil scars are usually about the same diameter of the orifice or upper neck of the bottle - like the blowpipe pontil scar which is discussed next - but for reasons unknown (unlike the blowpipe pontil scar which is explained next).  For more information click glass-tipped pontil.

Blowpipe ("Open") Pontil: This type of pontil mark, which was formed when a hollow blowpipe was used as the pontil rod, is at least as common on American made bottles as the glass tipped pontil mark.  Using a blowpipe as a pontil rod was likely done to both save on the number of tools used by the glass blower and to save time.  Blowpipe pontil scars were likely formed by two slightly different processes which would each be indistinguishable on the finished bottle:

• The likely commonest method was that the blown bottle was laid on a V-shaped table or structure, the blowpipe removed (cracked-off or sheared) from the bottle neck, the remaining glass around the end of the same blowpipe reheated, and then quickly reattached to the bottle base.  This process could have been done by one master glassblower ("gaffer") saving the labor cost of a worker to hold the pontil rod (Toulouse 1968; Jones 1971).
• The other possible method would have been the use of a second blowpipe (glass blowers usually had several at hand) which was dipped into the glass pot by the assistant, an appropriate amount of glass gathered around the sides of the blowpipe orifice leaving the orifice open, and then attached to the base of the bottle.  It is unknown at this point how common either method would have been, though the second blowpipe method would not have provided any labor saving over the use of the solid iron pontil rod noted earlier and was likely not as common as the "same blowpipe" method.

Click HERE to view an illustration of a blowpipe pontil in action.  When a blowpipe was used as a pontil, it left behind a distinctive ring shaped scar that is usually sharp edged, round to slightly oval, with a hollow in the middle that is roughly the size of the bottles orifice (circumstantial proof that one blowpipe was usually used for both blowing and empontilling).  The picture to the above right shows a very distinct, protruding, and sharp blowpipe pontil on a calabash shaped flask that was made by a New Jersey glassworks for Samuel Huffsey, a Philadelphian merchant in the early to mid-1850s (McKearin & Wilson 1978).  Click HERE to view a picture of this entire bottle.   For more information click blowpipe pontil.

Sand Pontil: The sand pontil scar was also a common method of empontilling a bottle for finishing, though somewhat less common on American made bottles than the other three primary methods described here.  This mark was formed when the hot glass on the tip of an iron pontil rod with a flared end was dipped in sand (or glass chips) prior to application to the bottle base.  The sand was apparently intended to keep the pontil rod from adhering too closely to the bottle, facilitating easier removal.  However, a larger connecting surface at the end of the pontil rod was necessary with this method in order to ensure an adequate adherence to the bottle base (Jones 1971).  The picture to the left is of an English made spirits bottle with a typically diffuse sand pontil, which are the multitude of small scattered specks outlining a rough circle within the middle portion of the base.  Click HERE to view the entire bottle.  Click sand pontil base to view another picture of a sand pontil on the base of a ca. 1850s American made liquor bottle.  For more information click sand pontil.

Bare Iron Pontil:  This type of pontil mark is the result of using a bare iron pontil rod with an appropriate shaped tip or head which was heated red hot and directly applied and fused to the base of the bottle to be held.  There was no glass added (like a glass tipped iron pontil rod) or remaining (like using the blowpipe for a pontil) on the iron tip of this type pontil rod.  Click HERE to view an illustration of a bare iron pontil attached to a bottle base.  Like the other pontil rod types, this one was probably removed by sharply tapping the rod near the attachment point.  The iron deposits which form the iron pontil mark are very small fragments or residue from the tip of the bare iron pontil rod itself. The picture to right is a particularly distinct iron pontil mark with ample residual iron left imbedded in the bottle base.  Click HERE to see a picture of the entire bottle which were referred to in glass maker catalogs as a "Gothic peppersauce" due to the ornate panels on the sides of the bottle (Whitall Tatum & Co. 1880).  For much more information click iron pontil.

"Combination" Pontil:  Occasionally found are bottles which appear to have two types of pontil scars on the base.  For lack of any previously defined term, it is being called here a "combination" pontil scar.  Only a small minority of pontil scarred bottles have "combination" pontil scars.  The bottle pictured to the left has an obvious bare iron pontil mark surrounded by a distinct glass tipped pontil scar (click on picture to enlarge for detail).  Click umbrella ink to view a picture of the entire bottle.

The reasons for this phenomena are unknown since the bottle only needed to be held by one rod for finishing.  The most likely answer is that the center of the glass tipped pontil rod fused to the hot base of the bottle leaving behind the iron oxide typical of a iron pontil scar along with scattered fragments of glass typical of a glass tipped pontil scar.  There is at least one other combination pontil variation; for more information click combination pontil.

Snap-case & Sabot:  The sabot and snap case were innovative and possibly revolutionary tools that replaced the pontil rod almost entirely during the 1850s and to mid-1860s (Scoville 1948; Munsey 1970; Innes 1976; McKearin & Wilson 1978).  Many different designs of these tools were used though the tool illustrated to the right would be typical of the general snap case design.  (Click on each picture to enlarge to a better quality version.)

Instead of affixing a pontil rod in some fashion to the base of the hot, post molded bottle (as described above) the handler (or servitor) used one of these non-empontilling tools to hold the bottle.  These tools usually left little or no markings on the bottle base or sides.  Sometimes a bottle will appear to have the surface texture of the body sides indented or roughed up by the tool or the sides slightly flattened by over-compression.  It is usually difficult or impossible to conclusively differentiate the subtle markings of a snap case or sabot from the array of possible mouth-blown mold or glass making imperfections.

The sabot (also called a "spring cradle") was the earliest version of a non-empontilling (i.e., non-bottle scarring) bottle holding tool and was developed in Europe possibly as early as the 1697, though probably not much used until the early 19th century (McKearin & Wilson 1978; Van den Bossche 2001).  This four-pronged tool was sized to closely fit the diameter of the base and lower sides of the bottle with different sized sabots apparently necessary for different diameter bottles.  The sabot likely made its way to the U.S. by the mid-1850s (Toulouse 1968).  An illustration of the sabot can be found in the book Antique Glass Bottles - Their History and Evolution (1500-1850) by Willy Van de Bossche (2001) which is still widely available.

However, the sabot was likely quickly replaced by the more versatile and easy to use snap case tool which could hold different diameter bottles due to moveable and/or interchangeable parts (McKearin & Wilson 1978).  A snap case was also known simply as a "snap" or as a "spring punte."  A common snap case tool had a center post which cupped the base of the bottle and at least two bars or flanges that grasped the sides of the bottle.  The three separate pieces were held together by a tubular sheath which when pushed up towards the bottle "snapped" closed onto the sides and base (see illustrations above).  A collateral benefit of the snap case is that it more securely held the hot bottle than any of the other methods allowing for the development of more sophisticated lipping tools (Deiss 1981).  Various types of snap case tools were used in the manufacture of mouth-blown bottles up until semi-automatic and automatic bottle machines effectively ended mouth-blown production and the need for such tools. An 1884 patent granted to Joseph B. Wilson for a "Clamp for Holding Bottles" is available by clicking Patent No. 294,946 which illustrates another version of an adjustable snap-case tool and a description of how it worked (U. S. Patent & Trademark Office website). 

For more information on the subject of snap case tools, consult the Bottle Bases page.

Mold-Blown Manufacturing (and related)

Introduction

This section deals with mouth-blown bottles that were not fully free-blown, but instead manufactured by processes where the bottle shape was formed substantially or entirely by some type of single or multiple part containment mold.  (An example of a "two-piece" mold from a 1906 glassmakers catalog is shown below left.)  This section also discusses various other mouth-blown bottle manufacturing methods, some of which (like finishing) were also used with the free-blown methods noted above.

To quote from Munsey (1970) once again, the following is additional molding specific information that notes the additional steps necessary in addition to the bottle blowing description noted in the free-blown section above (the following would be the fourth paragraph in the Munsey excerpt above):

If the bottle is to be blown in a mold, the gaffer receives the blowpipe with the gather on it from the servitor and stands in position over the specific mold to be used.  He then lowers the parison into the open mold.  If the mold is other than a dip or one-piece mold an apprentice will assist by opening and closing the parts of the mold at appropriate times.  After the parison has been lowered into the mold, the gaffer blows steadily into the blowpipe until he feels resistance which signals him that the hot glass has assumed completely the shape of the mold.  He immediately ceases blowing and after the mold is opened he removes the bottle from the mold, ready for finishing...  (Munsey 1970)  (Click molding a mouth-blown bottle to see an illustration of the described process.)

One of the more concise descriptions of the operation and work allocation within a typical late 19th to early 20th century glass blowing "shop" producing mouth-blown molded bottles is found in the book Machinery and Labor (Barnett 1926).  The following is quoted from the introduction to Chapter III, which is entitled "The Introduction of Semi-Automatic Bottle Machinery" (pages 65-66):

The manufacture of bottles and jars by the method of mold blowing is carried on by working units known as "shops."  In each of these there are seven persons - three skilled workmen and four boys.  Two of the men blow and the third finishes.  The blower takes a lump of glass from the pot or tank on his pipe, rolls and partially blows it.  The mold tender, a boy, opens an iron mold and the blower lowers the glass into the mold.  The mold having been closed, the blower inflates the glass to fill the mold.  The pipe is cracked off from the bottle or jar, which is then carried by another boy - known as the "snapping-up boy" - to the finisher, who shapes with tools the neck and lip of the bottle.  The third boy - the "carrying-in boy" - carries the ware to the annealing lehr.  A "cleaning-off boy" cleans the blow pipes of the blowers in preparation for re-use.  Variations in this arrangement are found.  In making some kinds of bottles, for example, a gathering boy gathers the glass for the blower, but the rules of the union have severely restricted this form of the division of labor except on very heavy ware.  (Barnett 1926)

The number of people involved in the organization of a "shop" was variable.  The great 1908 image to the above right is from a West Virginia glass factory and shows a gaffer (blower) at work to the far left with his crew.  This was also another typical mouth-blown shop crew working at the mold itself and 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 (Lewis Hine photo, Library of Congress).  This crew may have also included one or all of the other workers noted in the above description (finishers, carrying-in boy, cleaning-off boy) but were not included in the image.  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" (Library of Congress).

The following is a loosely organized collection of information designed to orient a user in the various methods and equipment used for producing mouth-blown molded bottles.  Most of the information found here is an abbreviated version of what is found in more detailed form on other pages; links to those pages are provided in each of the subsections.

Bottle Molds

The large majority of bottles produced within the time span covered by this website (early 1800s 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 (Atwater 1893; 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 (illustrated below on an old trade card) - 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 which often allow help facilitate age estimating of a bottle produced (Kendrick 1968; Munsey 1970).  An example of a "two-piece" iron mold from a 1906 glassmakers catalog is shown to the left. 

Dip molds:  The dip mold is a step up technologically 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 right 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 late 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).  A square dip molded bottle is pictured below right.

One-piece round dip molds would leave no classic 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, though this was likely uncommon.  Multi-sided dip mold bottles 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.  One piece clay molds were particularly common during the early days of American bottle making (Atwater 1893).  Wooden dip molds - another common pre-19th century mold material - had to be kept 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 often very difficult to distinguish from free-blown bottles.  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 (Atwater 1893; 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 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 as it is not pontil scarred and was found in western Oregon in the context of 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. 

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 multi-part molds to virtual disappearance around 1865 (Jones 1986).  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 sometimes 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 often faint striations on the glass surface in many places on the body, shoulder and neck.  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.   No pontil scarred examples of a turn-mold have ever been noted by the author, though are conceivably possible.  For more information click dip molds.

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 right 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 since the mold was used simply and 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 right.

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 earlier.   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 right (above and below) have swirled ribs indicating being twisted while blown.

The bottle pictured to the left 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 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.  These bottles were almost certainly used for liquor and a host of other liquid products (McKearin & Wilson 1978; Jones & Smith 1985).  For more information click pattern molds.

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 (flask to the right) of this ridge which shows just below the bottom of the neck and just above the pattern mold ridges.

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 left) 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 right above was 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 in the pattern mold section above 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 a bit further to the west.  The Pitkin style flask to the left 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.  For more information click half-post method.

Keyed & hinge molds:  After the dip mold, the simple or "true" two-piece mold (typically hinged or fitted) is probably the oldest of the mold types dating back to at least the first century A.D.  These molds could be shoulder height or full-height (like illustration to the left) and typically did not include any of the "finish" structure within the mold.  The two-piece mold was in use for making bottles in the U.S. by at least 1809 as bottles with well established dates of manufacture are known to have been molded this way (McKearin 1970).

Most types of molded bottles are frequently referred to by collectors and archaeologists as having been produced in "two-piece" molds even though the mold was likely composed of more than two separate mold sections (covered later).  The point being made by users of the term is that the body, shoulder, neck, and sometimes the base (as covered in this section) were molded by the two large and opposite sections of the mold.  Though usually not totally accurate it is a reference that is unlikely to go away because of its pervasive use.  In fact, many modern bottles were and are produced in molds that technically have up to nine different parts, but are still frequently referred to as having been produced in a two-piece mold (Toulouse 1969b).

The true two-piece "hinge mold" came in several different configurations which all had in common that there were truly only two molding sections to the mold, as illustrated above.  The classic two-piece hinge mold produces a bottle with a base that was equally formed by each half of the hinge mold, i.e., the base mold seam splits the base in to two equal and symmetrical portions.  The mold was either hinged on the side as illustrated above or hinged on the bottom so that the mold opened like a waffle iron.  Either hinging style produced bottles which are not physically distinguishable from each other since the location of the hinge leaves no trace on the produced bottle. 

The bottle pictured to the right was blown in a mold that functioned similar to the illustration above with the base formed in equal halves by each side of the mold.  The terms hinge mold base or snap case base are used by many to denote this configuration of the true-two piece mold.  Though these terms are nominally accurate - the bottles were produced in a hinge mold and a snap case tool was often used - these terms or methods also pertain to virtually all mouth-blown bottles since most all molds were likely hinged and some type of snap case tool held all molded bottles that were not empontilled.

Another configuration of the true two-piece mold, which varied from the mold illustrated above, were molds in which the two halves of the base - as defined by the still continuous though not straight base seam - were not equal in size.  As shown in the picture to the left (Dr. Hostetter's / Stomach Bitters) the entire depression area in the center of the base and bottom and right outer base edges were formed by a "flange" protruding from one mold half.  The remaining outer perimeter area of the base (left and top portions of base in the image), outside of the depression area, was part of the other mold half which surrounded and accepted the "flange" from the other mold half when the mold halves were pressed closed. These type of asymmetric bases are often referred to as having been made in a "keyed mold" or as a "keyed" base or "key mold" base (McKearin & Wilson 1978).  The utility of the "key" was in apparently allowing for a closer meshing and centering of the mold halves when brought together, similar to the post base mold discussed later.

Other variations of the keyed mold type have a much less pronounced arching of the one side of the base into the other or have a squared off "notch" that has abrupt right angles instead of rounded arching.  Click key mold base to view a picture of a ca. 1865-1875 patent medicine bottle with a more subtle rounded key mold base without a base depression.  Click notched base to view a picture of an early American (1840s) pint liquor flask (Pittsburgh, PA.) that exhibits the "notched" or squared-off keyed base flange on the base.  All these variations served the same function of centering the mold halves better.

Both of the basic styles of true two-piece mold bottles (straight and non-straight base mold seams) can be found with any of the four types of pontil scars overlaying the base mold seam, though the sand pontil is uncommonly seen on keyed bases.  Pontil scars would provide date bracketing opportunities as discussed previously on this page, i.e., these bottles would very likely date between about 1810 and the early 1860s.  All styles of true two-piece mold bottles largely disappeared by the mid 1870s allowing for a reliable dating end point for non-pontiled, hinge or keyed base bottles (Toulouse 1969b; Berge 1980; Jones & Sullivan 1989).  The one notable exception to this dating is that round bottom or torpedo soda bottles continued to be produced in true two-piece molds until the early 20th century.  Hinge mold bases can date back to at least 1810, but keyed bases appear to have originated in the late 1830s or early 1840s allowing for a relatively reliable begin date for this type of base (Toulouse 1969b; McKearin & Wilson 1978).  For more information click keyed & hinge molds.

Post base molds:  The date or origin of this style of mold is unknown, though it was used in the U.S. at least as early as the 1840s and as late as the early 1900s.  It was the dominant bottle mold type during the last third of the 19th century (Jones & Sullivan 1989; McDougall 1990). 

The post mold is actually a three (and sometimes more) part mold where the middle portion of the base is formed by a separate small plate or "post" with the neck, shoulder, body, heel, and outside edges of the base formed by the two side mold sections.  Sometimes the finish was also partially or totally molded (the later tooled finish post base mold bottles and most "ground top" fruit jars from 1858 on).  See the ground top discussion on the Finish Types or Styles page for more information.

The illustration to the right shows the configuration of one type of post mold with the post an integral part of a larger base plate. In this illustration, the post itself is the only part of the larger base plate that makes contact with the bottle base.  Click post-mold to view an illustration of another type of post mold for which the post is actually a individual mold piece that is attached to the base hinge of the mold.  As with the "key" or "notch" in the true two-piece molds discussed above, the function of the post was to orient and center the mold halves which would close around the outside diameter of the post (Toulouse 1969b). (Note: Like with the "true" two piece mold (hinge & key molds) noted above, these molds are also referred as simply a two piece mold even though there was at least a third base mold portion.)

A typical and distinctly "seamed" post mold bottle base is shown in the photograph to the right which is the base of a Warner's Safe Tonic (Rochester, NY) bottle that dates to between 1879 and 1883 (Seelinger 1974).  The mold base plate or post produces a round mold seam centered on the base like that pictured. (The pictured base also has the initials A. & D. H. C. which stands for A & D. H. Chambers Glass Company (Pittsburgh, PA.) which was in business from 1843 through the mid to late 1880s (Toulouse 1971, Lockhart pers. comm. 2004).)  Perpendicular to each side of the round post seam are straight mold seams which run to and around the heel of the bottle to become the side mold seams.  This picture shows well the typical base appearance of a post mold produced bottle. 

On a significant number of post mold bottles there is an apparent mold induced "edge" or mold seam at the upper edge of the heel that may appear identical to the heel seam produced by the cup base mold discussed next.  Some have called this a "cup-post bottom mold" because it has features of both mold types (Ayres 1980).  However, any bottle with the mold seam proceeding around the heel and onto the bottle base to mesh with a round/oval mold seam within the confines of the base is still considered a post mold bottle regardless of the appearance of a seam around the upper heel.  There is the possibility that some post molded bottles with an apparent mold seam on the upper heel are in fact a product of a hybrid mold type that had two moveable parts to the base plate: the regular round/oval post in the middle of the base and another circular plate surrounding the post that meshed with the side halves of the mold and did leave a true cup mold type mold seam at the heel.  Multi-part base plates are documented on the early Rickett's molds so there is some precedence to this notion (Jones & Sullivan 1989). 

It is thought more likely that on a majority of bottles with this feature that it is a function of the interface of two mold pieces permanently attached together at that point - i.e., welded or bolted and perpendicular to each other.  Specifically, each body half of the mold would have two pieces: one being the vertical body side section which extends down to the top of the heel where it would be permanently attached (welded/bolted) to the second part which was a flat horizontal plate with the "half-moon" cut-out for the post to fit in to.  There would be the potential of a mold seam formed on the bottle by the intersection of these two immovable mold pieces, though it is not a mold seam in the classic sense which was caused by the interface of two movable mold parts. This conformation is not specifically described in the literature but is inferred from photographs of different molds showing this possibility (McKearin & McKearin 1941; Kendrick 1968; McKearin & Wilson 1978).  Since the observed bottles also have an obvious post mold type base seam they would still be considered a post base mold product and would follow the dating guidelines noted in the Bottle Type & Base Related Dating Notes on the Bottle Bases page. 

In addition to the above variation possibility, there are several post mold variations or facts to be aware of, as described below:

• The post shape is usually round even on rectangular, square, or oval shaped (cross-section) bottles.  If not round, the post shape will be oval like the middle bottle pictured at this link: bottle bases.  An oval post has only been observed on oval or rectangular shaped bottles, though rectangular bottles have round posts.  Square or rectangular posts have never been reported or observed by the author of this site, though they could theoretically exist - and likely do, since it seems everything in the bottle identification world has exceptions.
• The post mold seam circle (or oval) is frequently hard or impossible to see or feel as it is often integrated into or masked by molded base features like a depression or shallow push-up.  In most cases like this the post is what forms the base depression on the finished bottle.
• If the post seam is not apparent on a bottle one is dealing with, look very closely at the heel to base transition area of the bottle.  A post mold is always indicated if the side mold seams curl around the heel of the bottle and proceeds at all onto the base of the bottle - even if the round/oval post seam is not obvious.  The picture to the right shows the distinct mold seams coming around the heel of the bottle and disappearing at the edge of a molded depression in the center of the base.  The post mold seam is largely invisible because it forms the edge of the depression, though it is slightly visible on the lower left side (click to enlarge picture).
• On many round (in cross section) bottles - particularly larger cylinder liquor bottles from the 1860s, 1870s, and 1880s and some soda/mineral water bottles dating back as early as 1850 - the post seam is difficult to see because it is on the outside edge of the base just around the edge from the lower heel of the bottle.  One has to look closely at where the side mold seam curls around the heel of the bottle to ascertain that it does indeed proceed onto the base and that there is a faint (or base feature masked) round post plate mold seam.  As noted, if the side mold seam runs around the edge of the bottle heel at all - even if it ends right at outside edge of the base - it is a post mold bottle.

Post molds were used to produce just about any type of bottles, with the majority of use of these molds made between the 1850s and the early 1890s.  However, similar to so many other aspects of historic bottle dating, there are exceptions or variations based on the type or style of bottle and even bottle size. This is covered in the Bottle Type & Base Related Dating Notes section of the Bottle Bases page.  For more information click post-base molds.

Cup base molds:  The origin of the cup mold (aka cup base mold) is unknown, though they appear to have been used at least as early as 1850, though pontiled scarred cup base molded bottles are very unusual (McDougall 1990).  Empirical observations indicate that this was the dominant mold type for mouth-blown bottles from the late 1880s to the domination of bottle making by automatic bottle machines by the late 1910s.  (Note: Most machine-made bottles were also produced in cup base molds; see the machine-made section below.)

The cup mold was also at least a three-part mold where the third piece was a base plate which had an shallow depression that "cupped" and molded the entire base and the lower heel of the bottle, though on earlier items (1860s and 1870s) it appears that the base plate was simply a flat piece of metal or even the floor of the glass works on which the two upper halves of the mold sat (Kendrick 1968; empirical observations).  (Note: For the purposes of this website, bottle molds with a flat or lacking base plate are considered cup-base molds since they do not fit any of the other noted mold configurations.)  The neck, shoulder, and entire body to the upper edge of the heel were formed by the two side mold sections, which unlike the post-mold, did not mold any of the actual base.  Sometimes the finish was also partially or totally molded in a cup mold, particularly with tooled finish cup mold bottles ("improved" tooled finish) and most "ground top" canning jars.  However, cup mold, mouth-blown fruit/canning jars are less common than post mold jars.  (For machine-made jars cup base molds were the norm.)

At the upper edge of the heel there is usually a mold line in evidence running around the circumference of the bottle.  This line indicates the interface between the lower edges of the side mold pieces and the upper edge of the cup base plate.  From this mold line - called a "bottom plate parting line" in the glassmaking world - the side mold seams branch off perpendicular (Tooley 1953).  Sometimes this heel mold seam is not obvious or visible and appears integrated into the heel edge of the bottle, though all cup molds had an interface of mold parts at the heel and the potential for a seam there.  The heel seam can also be non-existent on bottles from molds with the previously noted flat, non-cupped mold base plate or no base plate at all, i.e., simply the floor of the glass works (Kendrick 1968).  This seems to most commonly observed on the earlier "cup mold" bottles from the 1860s and 1870s which have a relatively sharp and almost non-existent heel (Kendrick 1968).  Click Smith & Davis druggist bottle base for an image of an early (ca. 1860) druggist bottle with this feature.

The illustration to the above right shows an idealized example of what a cup mold could look like.  As shown, the base and lower heel were formed by a depression cut into the base plate of the mold.  It was likely that the base plates were smaller than that illustrated, which is is based on mold replicas produced for and pictured in a Western Collector Magazine article by Dr. Julian Toulouse in the late 1960s (Toulouse 1969b). 

The image above right is of an actual iron cup base mold used for mouth-blown bottle production which most likely dates from the late 19th century.  This shows that indeed the entire base plate was smaller than the Toulouse replica, though the actual base forming portion was a relatively small elevated circular portion within which the cup indentation base form was machined.  This elevated portion would greatly assist in the easy centering of the mold halves when they were shut around the parison, much like the post of the post base mold.  It is not known for sure what type bottle this mold produced, though it appears to be a small medicine or ink bottle as the bottle the mold produced was only 1.25" in diameter and the height of the mold is only 3.25".  There appears to be no finish form engraved into the upper neck portion of the mold (i.e., the bottle would not have an "improved tooled finish") implying that the finish was either applied and tooled or tooled to shape with the refired glass just below the blowpipe removal point.  Click on the following links to view more images of this mold: view of the mold in the closed position; mold disassembled; close-up of the hinge mechanism. (Photos courtesy of Chuck Flexser.)

The bottle pictured to the left is a Cla-Wood Malt Tonic  (Clarke-Woodward Drug Co., Portland, Oregon) produced in a cup base mold during the early 20th century.   Click Cla-Wood Malt Tonic to view a picture of this entire bottle.  As shown in the picture there are no mold related seams on the base of a cup molded bottle which sets this type of molded base apart from the hinge, keyed, and post molded bottles which do have base mold seams.  There can be embossing on the base (e.g., makers marks, mold marks, product names) as well as mold air venting marks during the later end of mouth-blown bottle production (base air venting virtually always places a mouth-blown bottle after 1900).

Cup base molds were used to produce just about any type or class of mouth-blown bottles, with the majority of use made between the late 1880s and late 1910s when automatic machines dominated the bottle making market.  As noted, cup molds continued to be the mold type of choice on automatic bottle machines also (Toulouse 1969b).  However, similar to so many other aspects of historic bottle dating, there are exceptions or variations based on the type or style and even size of bottle.  For more information click cup-base molds.

Three-piece molds:  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 left 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 formed by glassblower manipulation.  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 making this an "improved" tooled finish.  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 green box below.  For more information click three-piece molds.

Three part molds 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 to the right.  It has three vertical mold seams from the heel to the roughly cracked-off finish rim 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.

Pictured to the left is a much earlier three-piece 'leaf' molded bottle.  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 also well disguised by the elaborate body pattern and are only obvious where a horizontal or diagonal line intersects the mold seam.  For more information click three-piece 'leaf' mold.

For additional information, see the discussion of three-piece molds on the