1990 Out of the Mold


Molds have been used to shape glass objects since ancient times. During the New Kingdom (1555-1090 B.C.) Egyptians appear to have made cast figures and fused inlays in molds. Casting by the lost wax method in two-piece, baked clay molds; fusing small canes of glass in clay molds; and sagging a circular disc of glass over a convex clay mold were methods of shaping glass used by glassworkers in the second half of the first century B.C.

The invention of the blowpipe about 50 B.C. revolutionized glassmaking, enabling glass to be mass produced. Almost immediately after the blowpipe’s discovery, glass appears to have been blown into a mold. The use of molds made possible the production of repetitive pieces of similar shape, size and design. These molds were made of baked clay and probably also of wood and metal. Simple cup-shaped molds, called dip molds, with their hollow interiors either plain or inscribed with ribs, were the first blow molds employed. The glassblower inserted a gather of molten glass into the mold and blew to inflate it against the walls of the mold. In this way the shape and design of the mold were impressed on the hot glass. After withdrawing the inflated gather, the blower would fashion the rest of the vessel with hand tools.

Complicated shapes and designs required more than one piece to a mold so that the inflated vessel could be withdrawn from the mold without distorting the pattern. Two-piece, three-piece and even five-piece molds were developed to aid in extracting the vessel from the mold.

Blown glass vessels of the first century A.D. were so common during the Roman Empire that even the middle and lower classes could afford them. Probably the most recognized Roman glassblower of mold-blown vessels was Ennion, who had carved into the design of his mold the words, “Ennion made it. Let the buyer remember.” His inscription is believed to be the earliest known maker’s name impressed from a mold.

Nothing is known about just who made the molds for these early glassworkers. Possibly the glassmakers made their own molds or used molds produced for them by local potters.

With the fall of the Roman Empire and the Dark Ages that followed, most glassmaking ventures ceased to exist. Small glass factories survived in the German forests and probably employed wooden molds during this period.

The revival of glassmaking at the end of the Middle Ages was centered around Venice. By the 15th century, pattern molds were being used in Venice and elsewhere on the Continent. Besides ceramic and wooden molds, copper and brass molds were also employed. By the 17th century, iron molds were in use in England. Jean Haudicquer de Blancourt in his book The Art of Glass, translated into English in 1699, also mentions the use of marble molds.The glassworkers employed at the first glass ventures in the Colonies were immigrants from the Continent and England. They brought with them their knowledge of glassmaking, which also included the use of molds. Wood, clay and metal molds were utilized. Two-piece hinged part-size metal molds with patterns such as diamonds carved into their hollow interiors were used by the early glassworkers at Stiegel and Amelung to produce diamond flasks and small tableware items.

The names of the makers of these early Colonial molds remain unknown. Every glass factory required skilled workers who had knowledge of ceramics and could fashion the clay pots used for melting glass. The pot maker would have had the know-how to create a clay mold. To operate a glass factory the skills of a blacksmith were also required to fabricate blowpipes and tools; the blacksmith would also have had the ability to make a mold. If the glass factory did not have its own blacksmith or metal worker, a local one could have been employed.

By the early 19th century, full-size two-piece brass and iron molds were utilized to make bottles and flasks. Full-size molds fashioned the entire body of the bottle, including the shoulders and neck. The only hand finishing required by the glassblower was that necessary to complete the mouth of the container. Bottle after bottle could be produced in uniform shape, size and capacity, with or without ornamentation. The shape of the bottle no longer depended upon the glassblower’s skill.

Full-size molds with three or more pieces were developed for containers of more complex shape. During the 1820s lightweight decorative tablewares that imitated cut glass designs called Blown Three Mold were blown into full-size molds of three or more parts.

The mechanical pressing of glass into molds, a process introduced in the late 1820s, revolutionized the glass industry. The first patents issued for this new process were for furniture knobs. Exactly what these early furniture knob molds looked like is not known because the Patent Office fire of 1836 destroyed the records. Probably they were simple one- or two-piece molds with a plunger. A gob of glass was sheared off the end of a gathering rod and dropped into the mold. The plunger was then forced into the mold by means of a hand lever, impressing the pattern of the mold into the soft glass.

The molds were probably cast in a local foundry proximate to the glass factory. Cast iron had become the preferred metal for molds by the early 19th century. It was more durable than soft brass. Iron casting was considered the premier technology of the Industrial Revolution and made mass production possible.

This new technology of mechanical pressing eliminated the jobs of skilled glassblowers. Semi-skilled laborers could press glass into the molds, and improved mold designs gradually replaced most hand decorating and finishing. The moldmakers, with their metalworking skills and problem-solving abilities, were now essential to the glass industry and indispensable for a factory’s success.

As time passed, larger glass factories found the need to start their own mold departments. Moldmakers were required not only to carve new designs into molds but also to keep the company’s expensive investment in molds in working order. Small companies depended on ordering molds from private moldmakers, who had set up business in the major towns of Philadelphia, Pittsburgh and Boston. Even companies with their own mold departments often found it necessary to order molds from the independent moldmakers.

Improvements in mold design and more efficient presses steadily continued with innovative patents by moldmakers. In 1903, Michael Owens patented the fully automatic bottle-blowing machine, which, like the blowpipe in 50 B.C. and the mechanical press in 1825, changed the glass industry forever. The automatic machine eliminated the jobs of the glassblower and his team, but it did not do away with the need for molds and moldmakers. The moldmaker was still essential to these newly automated glass factories. Molds were adapted for attachment to the machinery, but basically they were the same two-piece cast iron molds. Two different molds were utilized to make a container. The first was used for pressing the molten gob into the basic shape called a blank; this blank was then transferred into another mold, into which air was blown to inflate the container.

Today, molds are essentially made the same as they were over 100 years ago. Cast iron is still the preferred metal, with stainless steel often used for the plunger. Small hand shops often employ lightweight aluminum molds, which are easier to handle and less expensive. Mold shops employ computers and duplicating lathes, making the moldmaker’s job easier, but these artisans are still essential to the glass companies’ success.


The first molds used by 18th century Colonial glassworkers were dip molds with an interior shaped like a deep cup. These one-piece part-size open molds were made from clay, stone, wood and metal. Blowing into a dip mold helped impart uniform shape to the body of the article produced. The shoulders and the neck of the bottle had to be fashioned by manipulation with hand tools. Flat-sided bottles, such as gin bottles or snuff bottles, were blown into a paneled dip mold similar to a soapstone mold which was previously part of the collection of Ed Pieffer.

Simple designs of ribs or flutes were carved into dip molds, creating optical designs on the glass blown into them. The interior of the ribbed dip mold tapered inward slightly from top to bottom allowing for easy removal of the inflated gob. Using these decorated dip (today called “optic”) molds was an inexpensive way to ornament glassware. Two of three molds believed to be the earliest known American molds are a 16-rib dip cast iron mold and a 20-rib dip cast iron mold attributed to the New Geneva Glass Works, dating from about 1798 to 1847. Illustrated in American Glass by George and Helen McKearin, the molds are now in the collection of The Corning Museum of Glass.

The New Geneva 20-rib mold was probably used to decorate many different articles. A bowl with 20 ribs attributed to New Geneva and also in the Corning collection could presumably have been produced in this very mold.

Ribbed, or optic, molds were favorites of glassblowers. They could be as simple as a circle of nails pounded into a board or as involved and as decorative as a deep cast iron 18-rib optic mold used by Emil Larson. The glassblower could also use the rib mold to hold fine cooled rods of colored glass in the flutes. The hot gob of glass would be inserted into the mold and inflated, bonding the rods to the bubble’s surface. The article could then be fashioned to contain stripes or swirls of color.

More involved designs required more than one piece to a mold. Removing an inflated gob from a rib mold was easily done because the inflated ribs remained vertical and consistent with the ridges in the mold. A blown bubble in a diamond design could not be easily removed because the inflated matrix of lines would distort upon removal, coming into contact with the crossed ridges inside the mold. Small two-piece part-size pattern molds were used by many early American tableware manufacturers. Using pattern molds was again an inexpensive way to texture and give design to a one-colored glass article.

An example of a diamond pattern mold is the small two-piece brass mold, also from the New Geneva Glass Works and also dating from about 1797 to 1847. Sometimes referred to as a waffle mold, the mold was closed around the gob of glass, which the glassblower then inflated to impress the diamond decoration on the glass. When removed from the small mold, the glass was then fashioned into the desired article.

Pattern molds can have more than two parts. The use of three or more pieces to the mold made the inflated gather even easier to remove. A seam line was also impressed on the gather, corresponding to where the two or more sides of the mold met when closed. This line was often obliterated when the decorated bubble was expanded and shaped.

Part-size molds, both dip and pattern piece molds, are used by glassblowers today. Their versatility makes them important tools in every hand glass operation.

Full-size molds, used to shape the entire article, have been utilized since the 1st century A.D. Full-size two-piece molds with no interior decoration were usually made from hard fruit woods. They were used extensively by early American glass factories as a cheap way to fashion containers of uniform shape. A log of hard wood was split, then carved out and smoothed into the shape desired. When used by the glassblower, the wooden block was kept wet but would begin to char and burn, producing a steam layer which actually helped smooth the molten glass.

To use a full-size piece mold, the glassblower had to stand above the mold on a step, or the mold was placed in a pit in the factory floor. Another worker, called a “mold boy,” was needed to open and close the mold. The glassblower swung the gob of glass into the open mold, which was then closed around the glass by the mold boy. The blower then inflated the gob, all the while spinning the blowpipe slowly in his hands so that the glass was not sticking to the wooden mold and burning it. The experienced glassblower knew when the inflated gob was ready to be removed, and he tapped his foot as a signal to the mold boy to open the mold.The mouth of the container still needed to be finished. A small, solid pontil rod was attached to the bottom of the vessel, and the blowpipe was then removed from the neck of the piece. Hand tools were used to complete the rim of the mouth. No seam lines appear on these containers where the two mold parts met. By spinning the blowpipe, the glassblower had smoothed away any seam lines.

Wooden full-size hinge molds were inexpensive and easy to make. Their drawback, of course, was that they did eventually burn so much that the original internal shape was no longer intact and they had to be discarded. They were utilized to make bottles, vases, pitchers and so on. They were also used by cut glass companies to produce the blank forms that were then to be cut. Several of the wooden molds used by C. Dorflinger & Sons are in the Dorflinger Glass Museum collection.

A two-piece, full-size metal mold with interior decoration was used in the United States as early as 1809 for producing a Dr. Robertson’s medicine bottle for the Philadelphia druggist Thomas N. Dyott, M.D. made the mold and where the small bottles were manufactured are not definitely known. It is presumed that these medicines were blown at the old Kensington Glass Works of Philadelphia and later at the Olive Glass Works in Glassboro, New Jersey, in which, by his own account, Dr. Dyott owned an interest by 1815.

Small irregular-shaped, lettered medicine vials had been produced in full-size two-piece molds in England during the 18th century. Dr. Dyott is credited with the first large-scale use of full-size two-piece molds at his Kensington Glass Works and probably his Olive Glass Works. In 1831, Dr. Dyott’s Kensington factory, called Dyottville, had a mold house.

The use of two-piece metal hinge molds steadily spread until it became commonplace by the 1830s. They were not only used for consistency of shape but also because they could retain carved decoration and lettering. Brass and iron were the metals used. Of the two, iron was the more durable. The melting point of brass was very close to the temperature of molten glass. A brass mold could become so hot that it expanded, causing distortions in the desired design.

Probably the most important mold discovery in recent years is one half of a brass figured portrait flask mold. The mold part was discovered by Joseph Fliegel of Ashford, Connecticut, while exploring the banks of the Willamantic River, near the Mansfield Railroad Depot in 1968. The mold half’s interior depicts Lafayette in profile with the word “LAFAYETTE” in a semicircle above his head. Below the bust is a semicircle with the word “COVETRY” above “C-T.” Covetry is a misspelling of Coventry.

The comparatively scarce flask listed by the McKearins as GI-85 was produced by the Stebbins and Stebbins Coventry Glass Works of Coventry, Connecticut, by late 1824 or early 1825. The reverse design of the flask is an oval frame enclosing the French Liberty Cap on a pole with a semicircle of eleven five-pointed stars above the oval frame. Below the frame are the initials S & S for the firm’s name, Stebbins and Stebbins.

Attached to the back of the brass mold half is a cast iron triangular plate with a handle. The handle is slightly curved with a ring on the end. This iron plate and handle are badly corroded from long exposure to the elements. To attach the handle plate, the moldmaker or worker riveted through the brass with three cast iron tacks. The three corroded rivets are clearly noticeable on the interior of the mold.

Interestingly, two flasks can be found that correspond to this mold half. Lafayette GI-85 flasks with indentations corresponding exactly to the rivets’ position, as well as flasks of the same design without the indentations, are in many glass collections. Presumably, the handle was a later attachment. Why was a new handle necessary? Why mount the handle with rivets that altered the bottle’s surface? Answers to these questions we may never know.

A narrow band of cast iron, also corroded, was attached to the inside of the neck of the mold. Apparently, this attachment was to make the neck narrower. This is an interesting repair, illustrating how the stronger cast iron was utilized to keep the neck diameter constant.

Another important question is how did this mold open and close? It has no hinge on the bottom or side. The interior edge of the mold had four 3/4-inch long and 1/4-inch deep indentations. In all probability the missing half of the mold had four projections that corresponded to the indentations. What purpose did the ring on the end of the handle serve? The bottom of the mold has a hole with screw threads, suggesting that the part may have been mounted into a frame that controlled the opening and closing. The part also could conceivably have been mounted on a separate, detachable hinge.

More than a half-dozen retired and working mold-makers have inspected this mold. All were intrigued with the piece and puzzled about its closing. None came to a positive conclusion. Nevertheless, these questions do not diminish the importance of this mold.

We know that in at least one instance brass was definitely used to produce a figured historical flask. Cast iron was used in conjunction with the brass for a handle attachment and a neck repair. We also know that one example, a two-piece full-size mold, did not necessarily rely on a simple hinge to facilitate opening and closing.

Eight historical and pictorial bottle molds dating from 1850 to 1870 are in the collection of the Philadelphia Museum of Art. The molds were collected in 1901 and 1906 by Edwin Atlee Barber, then curator of the Philadelphia Museum and School of Industrial Art, with the cooperation of John Perkins Whitney, president of the Whitney Glass Works in Glassboro, New Jersey.

Three of these rare bottle molds were borrowed for this exhibition. All three are cast iron, two-piece molds with bottom hinges. This type of mold is variously called a bottom hinge, foot pedal or treadle mold and was used from 1810 into the 1880s. One half of the mold was bolted to the floor or side wall of a pit and attached to a lever or treadle with a foot pedal. The blower stood above the mold, controlling the opening and closing of the unbolted half of the mold by stepping on the pedal. Bottom hinge molds could also have one half of the mold bolted to the floor or pit wall and the other half controlled by the glassblower by means of a rod he held in his hand.

The Old Sachem Bitters and Wigwam Tonic mold from the Philadelphia Museum of Art collection not only is an excellent example of a two-piece bottom hinge mold, it also is marked on its exterior with the moldmaker’s name. The interior design of the mold is barrel motif, which was a popular design for bitters bottles. Between the upper and lower horizontal ribbed area is a smooth band on which the name of the bottle is inscribed. Attached to the back of the inscribed side of the mold is a handle and on the back of the other side is the bolt attachment used to secure the mold to the pit wall or treadle. On top of the bottom hinge is a round disc attached to the bottom of one side of the mold. It slides into the bottom of the mold’s opposite side to form a round concave base to the bottle.

On the exterior of one half of the Old Sachem mold is the moldmaker’s name, “George Mathewmann,” and his address, “55 First Street, Williamsburgh”. Miriam Mucha, Special Assistant, American Art Department of the Philadelphia Museum of Art, located Mr. Mathewmann in census and business directories as having maintained a moldmaking business in Williamsburg (Brooklyn) from 1856 to 1868.

Probably one of the most recognizable American bottles is the famous E.G. Booz Log Cabin bottle dating from 1860 to 1870. The two-part mold is a remarkable example of the problem solving skills of moldmakers. So that no visible seam lines ran down the walls of the building, the cabin was designed along a diagonal with the mold seams corresponding to the corners of the walls. The bottom hinge seam runs diagonally from corner to corner. The bottom hinge and center push up disc are independent of each other forming a rocking pin which helped the glassblower remove the irregular shaped bottle from the mold. The mold originally had sharp roof corners. The corners were filled in because of the difficulty of controlling the thickness of the glass in the high, sharp portions of the mold.

The third mold from the Philadelphia Museum of Art was chosen because it illustrates a major repair of a mold. The two-piece Calabash flask mold produced the Jenny Lind/Huffsey Glass Works flask GI-99. One half of the mold has a bust of Jenny Lind surrounded by two laurel branches and bears her name above the arched branches. The reverse is incised with the inscription “Glass Work’s” above a glasshouse with “S. Huffsey” carved beneath.

Examination of the exterior of the glasshouse leaf reveals the alteration in the mold. A plug with the inscribed word “Glass” had been bolted to the mold, filling a hole that had been cut to remove the old misspelled word beneath. Also on the inside of the leaf the letter “G” above the smokestack had been filled in but is still visible. What word or words had been removed?

Again Miriam Mucha did research, which revealed that the mold had actually been altered three times. The mold has been attributed to the Philadelphia moldmaker Philip Doflein, who has been credited with originating the Calabash (gourd shape) flask design. The mold, when first designed, had no lettering; only two related unlettered flasks are known. The mold was then inscribed, probably by Doflein for the Millford Glass Works of Millford (today Kresson), New Jersey, between 1846-1853. “Millford” was misspelled as “Millfora” in the mold. Nevertheless, flasks were produced from the mold. When the company’s assets went for sale in 1855, it is believed that Samuel Huffsey purchased the mold and had it altered with his name, probably by Doflein. The word “Millfora” was removed and replaced by a plug engraved with the word “Glass,” the “G” filled in and “S. Huffsey” inscribed below the factory building.

These alterations reveal several important clues about molds and moldmaking. As stated earlier, it is Philadelphia moldmaker Philip Doflein (working from 1842 to 1899), and not a glass company designer or customer, who is credited with designing the new bottle shape called the Calabash. A mold was a considerable investment for a glass factory because even though the company’s name was misspelled, the company still put the mold into production. Thirdly, it must have cost considerably less to have a skilled moldmaker alter a mold than to have your own mold design produced.

All three of the cast iron molds from the Philadelphia Museum of Art have very narrow walls. They range from 3/8 inch to 3/4 inches in thickness. Thin metal walls got hot very quickly and had to be cooled often, slowing down production. The walls were probably purposely kept thin on bottom hinge molds so that the glassblower could easily operate the treadle or foot pedal. Eventually, thicker walls that maintained even heat became the standard for bottle molds.

Another small bottom hinge mold included in the exhibit is an eight-panel inkwell. Marked on the bottom rocking hinge disc is the initial of the Whitall Tatum Company of Millville, New Jersey. Whitall Tatum opened its own mold shop in 1854.

Virtually all free blowing of bottles was eliminated in America with the development of the two-piece mold, which was being used to produce tableware by 1825. Glass company owners and moldmakers were constantly trying to develop new molds that would increase production and decrease expenses.

Probably the most revolutionary invention that first used more than two pieces to a mold was designed by Henry Ricketts of Bristol, England, in 1821. The mold consisted of an upper part of two pieces that formed the shoulder and part of the neck. The lower section of the mold was a cylinder with an open space in the bottom for the mechanical punty. The entire mold and apparatus was mounted in a frame and placed in a pit. It operated by means of a foot pedal. The invention guaranteed the production of bottles of identical shape and size. The addition of an engraved ring to the bottom of the mold, made it possible to emboss the manufacturer’s name on the bottom of the bottle. This type of mold was quickly adopted by glassblowers and used well into the 1920s.

Little changed in the production of bottles until the early 1860s brought the introduction of the snap case. This new tool, a rod with either a spring device or simple can attached to its end, was used to hold the bottom of the bottle while the neck was finished. The snap case increased bottle production by eliminating the pontil and its rough mark.

The design of bottle molds remained the same until 1869. Homer Brooke, a Brooklyn moldmaker, patented a mold with a side hinge and a base plate. The base plate had a pedestal which formed the bottom of the bottle as the side pieces closed around it. This new mold design virtually eliminated the bottom hinge mold. A mold boy opened and closed the mold while sitting in a pit or on a stool. The walls of the mold could now become thicker, so that the heat was evenly dispersed.

Another important improvement in bottle molds was patented by Gustavus Storm of Philadelphia in 1875. He patented the design of a removable plate that could be engraved with personalized lettering. The bottle shape stayed the same but the plates could be changed for different customers. The interchangeable plate attached to the mold with a bolt in a manner almost identical to that used in the repair of the Millfora flask. The process for using removable plates had been used in molds for some time; Storm’s patent made it more convenient. An example of an interchangeable plate or slug plate mold is the cylindrical jar with opening for an oval lettering plate.

Personalized bottles for patent medicines and pharmacies were a major part of the production of bottle glass factories. Having a personalized mold produced was an expensive proposition for a pharmacy. With the Storm patent, the customer had to pay only the cost of the slug or lettering plate. Shapes of bottles became standardized to fit many of these plates. The Whitall Tatum Company of Millville, New Jersey, offered its clients in 1880 over 68 different designs of lettering plates.

Another type of two-piece blow mold is a “Paste Mold”. The name refers to thin-walled iron molds with an inner paste-like lining that allows the glass to be revolved during the blowing, eliminating all seams. The paste was usually made of resin, which was brushed onto the interior of a hot mold and then sprinkled with a carbonizing material such as sawdust or cork. The mold had to be baked to fuse the paste to its interior surface. Minimizing the wear on the metal, the paste consequently prolonged the mold’s life.

Paste molds were usually utilized in making chemical wares, chimneys and bottles. The mold was thoroughly saturated with water before each piece was blown. An inflated gather was inserted into the wet mold, and the mold was closed by the mold boy. As the blower blew the glass gob to conform with the closed mold’s walls, he continuously twirled the blowpipe. The wet lining formed a steam cushion when it came in contact with the molten glass, smoothing the surface. These molds had to be pasted every few hours.

More complicated blow molds were developed but basically the concept of how the mold worked stayed the same. More parts were added to a mold depending upon the complexity of the container’s design. Remarkably, probably one of the most complicated molds ever produced was saved from the scrap metal collection drives of World War II and is in the collection of the Museum of American Glass. The mold produced a building inkwell which was sold as a souvenir at the 1876 Centennial Exposition in Philadelphia. The building is Memorial Hall, the only Centennial Exposition building still standing in Fairmount Park. The intricate mold was designed by Emil Herckner at the Whitall Tatum Company in Millville. Eight movable parts make up the building’s walls and roof, and a large plate forms the base. Four top pieces form the complicated roof line and columns. Four side pieces shape the walls with incised window designs. The large bottom plate is marked “Patent April 11, 1876.” It had to be an extremely skilled glassblower who blew these bottles. He had to hold the inflated bottle in position while the mold boy opened the complicated parts so that the bottle could be removed from the mold.

The automatic bottle blowing machine patented by Michael Owens in 1903 eliminated the need for skilled glassblowers. Owens’ machine utilized a two mold process. The first was used to form the general shape of the bottle called a blank. This blank was then placed into a second mold, into which air was forced in order to inflate the blank to conform with its walls. The machine manipulated and transferred the glass, eliminating the need for glassblowers or mold boy. The machine controlled every aspect of fashioning the desired container.

Cast iron molds were made for the automatic machine by the same moldmakers who had made the blow molds for glassblowers. These new molds did not need handles or hinges because the machine controlled all movement. Owens’ machine may have replaced the job of a glassblower but it could not displace the moldmaker and his molds.


The United States is credited with the invention of the mechanical pressing of glass into molds in 1825, revolutionizing glassmaking by making possible the mass production of glassware. This new process eliminated the need for an expert glassblower to fashion a piece of glassware. An unskilled laborer could be trained in a few weeks to become a good presser. The technology utilized to produce blow molds was adapted to make press molds.

Pressing, forcing glass into a mold, had been used by ancient Egyptians in the 14th century B.C. to make small figurines. Over three millennia later, glass stoppers and drops for chandeliers were pinched in small hand presses in 18th century Europe and America. A similar tool to these pincers is a hand tool that fashions a walnut-shaped ball which could then be applied as decoration to a vessel.

Pressed bases used as feet for wines or as pedestals for vases and bowls were produced in England and America in the 18th century. Called “lemon-squeezer” bases, these supports were long thought to have been made by hand tools similar to the stopper pincers. Ken Wilson recently proved that these bases were pressed into a square mold with a hand tool that produced the domed ridged hollow interior.

Where and exactly when the table press with plunger, lever and mold was invented is not known. The Patent Office fire of 1836 obliterated much of the record. What record is left lists a patent for glass furniture knobs by John P. Bakewell of Pittsburgh on September 9, 1825. Most authorities credit Bakewell with the first pressing patent, even though the record never mentions pressing. Subsequent patents mentioned pressing into molds.

These furniture knob or door knob molds were probably very simple, made of one or two pieces. The molten glass was dropped into the mold, into which a plunger operated by a lever was driven. The plunger forced the glass into the interior recesses forming the door knob shape. There was no standardization of molds and presses in the different glasshouses that adopted this novel process in the late 1820s. Each press was more or less unique.

Subsequent patents were issued to individuals for improvements in molds and manufacture. On October 16, 1827, Phineas C. Dummer of Jersey City received a patent on the construction and use of a mold with a core for pressing glass into various useful forms containing a coverplate called a Dummer’s scallop. This coverplate very likely could have been a cap ring or rim, a significant contribution to mold development. The cap ring fit on top of the mold preventing the glass from overflowing the edge of the mold. On the same day a second patent for pressing was issued to Phineas C. Dummer, George Dummer and Joseph Maxwell. To date, only two pressed glass pieces, both salts, have been attributed to the Dummer firm.

Small cup plates were produced in several different ways, varying from right side up with the design carved on the bottom of the mold to upside down in a smooth mold with the design engraved on the bottom of the plunger. Depending upon the particular mold design employed, small fins of glass remained around the edge of the dish. The cap ring, which sat on the top of the mold, was engraved with the rim design and helped to confine the molten glass within the mold. By the 1830s, designers and moldmakers had realized that cap rings and plungers of different patterns could be interchanged while employing the same base mold. Contemporary reproduction cup plates, pressed individually, still utilize the same mold arrangement. The cup plate is pressed upside down into a smooth mold. An interchangeable die engraved with a commemorative motif is tooled to be fitted into the plunger. The scalloped-edged cap ring, sized to the fit top rim of the mold, can be changed to suit the customer.

As the number of glass houses pressing glass increased, so did the number of patented mold designs and improvements in the mechanics of glass presses. As early as 1834, one glass firm, the New England Glass Company of Cambridge, Massachusetts, was operating sixty to seventy glass presses. Hundreds of molds would have been needed to keep the presses in operation. By 1865, Deming Jarves, in his book Reminiscences of GlassMaking, estimated two million dollars had been expended on the molds and machines used for pressed glassmaking.

Molds of two, three, or more parts were developed depending upon the complexity of the desired article’s design. The moldmaker had to address the problem of the mold seams these multiple parts created. Disguising the seam within the pattern was the easiest way to eliminate the lines; consequently, moldmakers patented unorthodox molds with complex parts in order to do away with seams.

Depending upon the desired design, the plunger, which forced the glass into the mold, could be smooth or engraved with a pattern. A striking example of an engraved plunger is the huge plunger which forms the “Holly” motif on a bowl or plate. The design was originated by The Fenton Art Glass Company of Williamstown, West Virginia, and was first marketed in 1911. The mold also utilizes a large cap ring which produces the serrated rim. Important mold designs were patented but few of these innovative molds have survived. We have only the patent drawing to show us the remarkable problem-solving skills of the moldmakers. One mold that has survived is very similar in form to a mold design patented in 1841 by Hiram Dillaway of the Boston & Sandwich Glass Company. The mold pressed a wheel of stoppers by forming a cup, or cog, when the plunger forced the glass into the mold. When cooled, the stoppers were cracked off the cup and the cup was discarded. This mold made producing stoppers more economical.

Another significant mold development introduced during the last quarter of the 19th century was the so-called “cut and shut” mold. Before the invention of this mold design, it was impossible to press an object such as a cruet because of its narrow neck. A press mold could operate only with a plunger that was straight sided or tapered so that the plunger could be easily released from the interior of the mold. A cruet or syrup container was fashioned with a narrow neck that prevented a plunger from exiting the pressed form. These narrow neck containers had to be blown in a mold.

The cut and shut mold pressed a cruet upside down. The end of a tapered plunger shaped both the neck and the narrow opening at the spout. A wide collar of glass was formed at the bottom opening of the cruet. When removed from the mold, the cruet, held in a snap case, was warmed and its open end closed shut. The excess glass was sheared off, leaving a swirled mark, mistaken by many collectors for a pontil mark. Although the cruet had to be closed by hand, the process sped up production, eliminating the need for a skilled glassblower.

Few cut and shut molds survive. One that produces a “Hobnail” cruet is still in operation at The Fenton Art Glass Company. A hard wax form sitting inside the opened mold illustrates how the cruet is formed before it is removed from the mold.

Thousands of molds were designed and patented. As the pressing mold became more intricate, new and better presses were developed. Improvements were also made in the quality of the cast iron. Michael Sweeney of Wheeling, West Virginia, on January 4, 1966, patented the use of chilled iron for glassmaking molds. Developed during the Civil War for cannons, this iron contained chilled iron, which produced a hard, closer-grained metal. This new iron reduced the tendency of molten glass to stick to the mold.

Many moldmakers, such as Hiram Dillaway and Washington Beck, also introduced important press designs. Production was increased with the development of rotary table presses which could hold multiple molds, thus increasing production. Semi-automatic machines were in operation by the 1890s.

After the introduction of the Owens Automatic Bottle Blowing Machine in 1903, automated pressing machines were developed. Just as the glassblowers had been replaced by the machine, so were the pressers and shearers. Molds were developed to be attached to the automatic machine. The machines sheared off the gob of glass into a mold and then mechanically forced the plunger into the mold. All objects could be manufactured from tablewares to insulators to stoppers.The automated machine could also completely control the movement of the plunger. The insulator No. 43 mold, used by the Hemingray Glass Company of Muncie, Indiana, illustrates a fully automated machine mold. The plunger has screw threads embossed on its surface. The plunger, controlled by the machine, was slowly twisted into the mold, impressing the threads on the inside of the insulator.


The men who made the molds have long been overlooked by glass collectors and historians. Little was recorded about these early 19th century workers who helped revolutionize an entire industry. Presumably, the pot makers, essential in every glass factory for constructing the melting pots, fashioned the clay molds. Metal molds of brass or iron were probably manufactured by a blacksmith who either worked for the glass factory making tools or had his own business in the local town. A nearby foundry would also have been relied upon to make these early molds.

Most glass company owners quickly established their own machine shops not only as a way to produce their own molds but also to safeguard against the competition. The majority of the metal workers who worked in these shops are unknown, but their creativity and problem-solving abilities can not be overlooked. Without engineering degrees, they created complex molds and the machinery that controlled the molds.

By the early 19th century the creative center of the glasshouse was now the mold shop. The machinist or moldmaker worked closely with the manager and company owners to develop new equipment. Intense competition resulted in the invention of faster presses with multiple molds to increase production. Every new problem which arose was a challenge for the machinists.

Patent office records reveal the names of many moldmakers associated with glass companies. The list includes Hiram Dillaway of the Boston and Sandwich Glass Company, Joseph Magoun of the New England Glass Company, Daniel Ripley of Ripley & Company, Thomas Atterbury of Atterbury & Company, Robert D. Haines, assignor to the Boston Silver Glass Company, and many more.

Original patent drawings and models created by the mechanical genius Hiram Dillaway have been preserved at the Sandwich Glass Museum. A patent model for a mold with a reservoir that held water which cooled the mold while in operation illustrates Dillaway’s remarkable understanding of the difficulty of working early press molds. A hot mold caused the glass to stick to the walls of the mold, slowing production.

Independent mold shops were opened in the glassmaking centers of Boston, Philadelphia, Pittsburgh, New York and Baltimore by the 1850s. At least two independent moldmakers, Joshua Laird of Pittsburgh and E.M. Bartholomew of Boston, were producing molds in the late 1820s. Smaller glass houses without mold departments ordered their molds from these independent shops. Even larger companies with their own mold shops often could not keep up with their mold needs and also ordered molds.

Pittsburgh, with its iron and steel foundries, had the largest number of independent mold shops. Probably the most prolific of these independent shops was the firm of Washington Beck, which operated from 1859 to 1887 and shipped molds to Canada, Japan and the glassmaking countries of Europe.

Other noted Pittsburgh or Midwest moldmakers who operated independent shops were Henry Franz, William S. McKee, Julius Proeger, Andrew Thompson and Stephen Hipkins. Hipkins established his mold shop in Martins Ferry, Ohio, in 1884 and continued to produce molds until the 1940s. This shop is credited with making molds for more than thirty glass houses.

In Philadelphia, Philip Doflein probably set up the first mold shop in 1842. Recognized for developing the Calabash shape flask, he probably supplied many of the South Jersey bottle factories with molds. Charles Yockel also established a mold shop in this city.

Charles Yockel, first listed as a moldmaker in 1862, was in partnership with John Weidig until he opened his own business in 1875. His sons succeeded him and continued to operate the shop until 1946. Yockel produced presses and predominately molds for the bottle trade.

The interest in Charles Yockel stems from his papers that were saved and dispersed; many of them reside in the manuscript collections of The Corning Museum of Glass, Henry Francis DuPont Winterthur Museum and the Museum of American Glass. Many stationery letterheads of companies that Yockel produced molds for were published by Scott Tyson in 1971. The correspondence reveals not only the prolific nature of Yockel’s business but also the needs, and often demands of his customers. The orders and replies disclose prices and often reveal the length of time it took to produce the molds. Yockel advertised himself as a “Practical machinist and Glass Mould Maker, manufacturer of every description of moulds and presses for the Production of Blown and Pressed Glass.” He also stated that “I have constantly on hand the largest variety of Patterns of Druggist, Perfumers Bottles, Fruit & Pickle Packers, Patent Medicine, Flasks, Demijohns, Liquor Dealers Moulds & C., Table glassware. Kerosene Lamps, Lamp Chimneys, Goblets wine tumblers & C.” In 1891, a Yockel mold catalog noted, “We are the largest mould manufacturers east of Pittsburgh and make more Bottle Molds than any two mould shops in the United States.”

There is much more to be learned from Yockel’s papers. He supplied molds to major glass manufacturers across the country, such as Whitney Glass Works of Glassboro, New Jersey; Union Glass Works of Somerville, Massachusetts; Ellenville Glass Works of Ellenville, New York; Swindell Brothers of Baltimore; Gillinder & Sons of Philadelphia and more. Letters also pertain to business with foundries, other moldmakers, like Washington Beck; and directives from the American Flint Glass Workers Union.

Prices for Yockel molds in 1883 averaged $10.00 for a 3-ounce round or oval bottle mold and $22.00 for an oval quart mold. Lettering plates for molds cost 6 cents per plain block letter and fancy letters cost 10 cents. Standard prices for molds were set in 1891 by Yockel and seven other independent mold shops.

Attempts to unionize glass workers in the United States first began in the 1830s. On January 1, 1879, the American Flint Glass Workers Union was formed and by 1896 the Blowers League was known as the Glass Bottle Blowers Association. The machinists and moldmakers working in glass factories were not organized into these early unions. The average daily wage in Pennsylvania for moldmakers was $2.43 in 1879, $3.19 in 1880, $3.28 in 1881 and $3.33 in 1883. Pressers who operated the molds were making a dollar more per day on the average.

By 1885, moldmakers had gained membership in the American Flint Glass Workers Union. But they were still not well organized in 1911. The Flint Union molds bear the mark “A.F.G.W.U.” The Glass Bottle Blowers Association established a machine and press work department in 1899. Presumably not all independent mold shops unionized. Yockel’s shop in Philadelphia was unionized, but the Husted Hall Mold Works of Bridgeton appears not to have been organized.

The wage for an American Flint Glass Worker Union moldmaker in 1931 was 75 cents per hour. An apprentice earned 15 cents per hour which was the same rate earned by a mold boy who sat opening and closing a mold all day. When President Roosevelt instituted his National Recovery Administration in 1933, wages for moldmakers were raised by 40 cents an hour. During World War II, wages were frozen. After the war in 1946 a moldmaker received $1.15 per hour.

Today, the many jobs once performed by a single moldmaker are divided into separate tasks and separate job descriptions. Machines, like duplicating lathes and computers, have eliminated many responsibilities of the workers; yet even today molds are smoothed individually with files and riffles by vice hands and polished with emory paper by smoothers. Molds are in constant need of repairs which can be performed only by experts. The mold shop for the large Wheaton Glass Company has 80 employees. The mold shop is still the creative center of the glasshouse and critical to the company’s glassmaking process.


All molds began with a design. Within a glass company, an owner, agent or designer could create an original design, or the design could be supplied by a customer. Independent moldmakers also conceived their own designs from flask forms to uniquely shaped patterned pressed glass. The designer had to have a basic understanding of the material’s limitations when designing in glass. Today, designs are created on computers that detect difficulties in the motifs and adjust them.

The design was then given to the pattern or model maker. A model of the desired article was fashioned in wood. Many important wooden pattern models were saved and are in museum collections. A Plaster of Paris mold was usually made from the model to aid in casting the mold. In early mold shops, moldmakers were also pattern makers. Current models are made of a clear lucite which is durable and glass-like.

The pattern and plaster castings were then sent to the moldmaker. Just who decided how many movable parts were needed to produce the desired article is not definitely known. Probably the designer, pattern maker and moldmaker all worked together to solve the puzzle. Since an early moldmaker was also the pattern maker, he would have decided on the number of hinges and the method of arranging the component parts. In modern factories, the designer provides the moldmakers with blueprints drawn by the computer with the component parts included.

For a simple two-piece blow mold, a mold shop would already have on hand solid cast iron blocks with basic cavities ready to be chipped or carved by the moldmaker. A more involved mold for pressed pattern tableware required that the wooden model or plaster model of the mold to be sent directly to the foundry. A cast metal mold with a rough pattern cavity was made from the models.

Next the castings were then returned to the moldmaker. The mold pieces were shaped, fitted and smoothed. Hinges were machined and fitted with pins. Where each section fitted together, the surfaces were smoothed so they would close as perfectly as possible to eliminate mold seams. Vent holes were drilled through the mold walls where necessary. The mold was now ready to have its pattern carved into its interior cavity.

The finishing work was done by the chipper or vice hand. Chippers were artists who possessed the sculpting skills necessary to carve intaglio designs with chisels, riffles and files. Patience was probably one of the most important requirements for a chipper. Monroe Husted, who presumably worked in the mold shop of McKee Glass Company in Pittsburgh before 1905, drew three drawings of glass patterns he was chipping into molds. Each article of glass drawn also lists the number of hours it took Husted to engrave the designs. A simple punch cup mold in the “Colonial” pattern with garlands took 87 1/2 hours to produce. The second illustration is of an unknown pattern covered butter lid which consumed 378 hours of Husted’s time. The third drawing is of an “Aztec” pattern covered butter lid which took 228 hours to carve.

The McKee Glass Company sold the “Aztec” pattern from 1901 until 1927 and would have required multiple molds of each item to keep the pattern in stock. A McKee “Aztec” covered butter lid mold is in the collection of the Museum of American Glass. In 1953, the mold was sold to John Kemple who used it to produce reproductions. In 1969, the Wheaton Historical Association purchased the Kemple molds. The mold, drawings and reproduction lid illustrate the amount of time and the patience required to shape an intricate pattern into a mold.

When the chipper was finished his tedious task, the mold was virtually ready to be put to use. The plunger was fitted and the mold was then inspected. If all appeared correct, the mold was put into operation. Contemporary mold shops make castings in plastic steel from a lucite model. The cast impression is attached to a duplicating lathe which traces and carves the pattern into a block of cast iron with a similar blank cavity. The duplicated mold is then attached to a multiple duplicating lathe to fabricate several sections at the same time. Manually, vice hands still use riffles or files to smooth the pattern and emory paper to polish the surface. The mold is then inspected and sent to the glasshouse to be put into operation.


Molds have been an integral part of glassmaking since the first century A.D. Their importance has been overlooked for centuries. In the 19th century, molds helped revolutionize glassmaking because of their ability to be used for mass production. The moldmaker had become the creative force in the glasshouse.

Much of the history of molds and their technology has been lost. More research is still needed to better our understanding of molds and their nameless makers. It is hoped that this exhibition will stimulate further scholarship in completing the story of molds.