At the Lamp
All About Glass
Today lampworkers %%melt%% borosilicate glass in brilliant colors using modern torches that burn oxygen and propane. But how did glassworkers %%melt%% glass at the flame 300 years ago? As a glass librarian and a glass artist, I'm fascinated by the ingenuity and inventiveness of lampworkers in the seventeenth through the nineteenth centuries. The Rakow Research Library of The Corning Museum of Glass has a number of rare books — the "how-to" manuals of their day — that provide evidence for the types of equipment used by lampworkers of the past.
In the seventeenth, eighteenth, and nineteenth centuries, lampworkers were creating elaborate altars (as shown in fig. 1), centerpieces, and delicate Nevers figurines, as well as scientific glassware and lenses. Diesing's elegant lampworker in Die Glasschmelzkunst bey der Lampe, published in 1769 (fig. 2), is surrounded by a variety of wares ranging from barometers and scientific apparatus to glass eyes, elaborate birds, figurines, flowers, and centerpieces.
Some [lampworkers] apply themselves particularly to the construction of philosophical and chemical instruments; others occupy themselves with little ornamental objects, such as flowers, &c. and among the latter, some manufacture nothing but pearls, and others only artificial eyes.
Imagine you are a lampworker in the early eighteenth century. How might you set up your "studio"? In 1738 George Smith describes the process in his textbook, The Laboratory, or School of Arts (fig. 3):
First provide yourself from the Glass Houses with several Pipes [tubes] of Glass, that are hollow on the inside, of several Colours, and different Sizes; then you must have a Table, as you see represented in the Plate annexed. A is the Lamp, which is furnished with Rape or other Oil, and a large Wick of twisted Cotton; below the Table is a Bellows, B. When the Artist treads the Treadle fasten'd to the Bellows, the Wind will be convey'd through the Pipes under the Table to the small pointed opening by C, directly against which is plac'd the lighted Wick of the Lamp, D. The Smoak which issues forth from the Lamp, is convey'd through a broad Funnel made of Tin or Wood, E.
The Wind which strikes in a sharp Point against the Flame, occasions such a violent Heat that it will dissolve the most stubborn Glass, and you may, after you have soften'd the End of your Pipe in the Flame, blow through the hollow thereof, and form with small Plyers and other useful Tools whatever you please: small twisted Nooses of Wire are very convenient to hold your Work in, in order to shape and join different Colours to one Piece. The whole Art depends chiefly upon Practice.
The illustration by George Smith from his 1738 chapter "The art of blowing glass in miniature" (fig. 3) is not labeled alphabetically, but Johannes Kunckel's 1679 %%engraving%% (fig. 4) is:
- A — table around which four people may work at once
- B — the lamp, filled with oil and a strong cotton wick
- C — hole where the tapered blowpipe is attached . . . so that the air is directed onto the flame acute & concentrated, producing a flame that will %%melt%% glass. Goldsmiths have a similar system for soldering %%metal%%.
- D — bellows, attached to pipes of tin that are hidden under the table
- E — lever, attached to the foot pedal
- F — ventilation hood
- G — foot treadle for the bellows, pressed by the worker
Lamp workers, including chemists, hobbyists, and itinerant glassmakers, generally used lampworking tables (workbenches) similar to those illustrated in Smith and Kunckel. Many tables are shown with a place for a lamp on all four sides of the table. One person operated the bellows that supplied air to the four lamps.
Those working in cottage industries, including beadmakers and families producing small decorative glass items, most often used tables that were small enough to fit conveniently in a corner of the worker's home. The father was likely to run the bellows for the rest of the family, with the women and children around the table together.
Tables usually featured drawers where the glassblower's hand tools could be kept. Hand tools tended to be simple and handmade. Authors mention pliers, tweezers, scissors, and wire clamps, for example.
From the start, lamp workers have been improvisers. They adapted a commonly used lighting device to %%melt%% glass with its flame. The "lamps" illustrated are typical of the period. They featured a pear-shaped %%metal%% pan with metal sides and a hinged or pivoting lid. The pan was filled with fuel, and a twisted cotton wick was inserted into the oils or liquefied animal fats often used for fuel.
The lamps shown in Denis Diderot's plate Emailleur G.la Lampe (fig. 5), published in the late 1700s, show (1) the %%metal%% knife used to separate tubing; (2) the lamp viewed from the top; (3), the side view of the lamp, with hinges open, separated from the lower basin and (A) an insert to hold the wick in place; (4) the lower pan or basin; and (5) the lamp with its %%blowpipe%% in operation, air running obliquely to the flame.
According to Danger, combustibles included wax, olive oil, rape oil, and poppy oil, as well as tallow and other animal fats and oils, such as bone oil and fish oil. Purified rape oil was Danger's favorite versus animal oils, which do not give as much heat and "exhale an odour which is extremely disagreeable." Smith also notes the widespread use of rape oil. Cotton wicks were common and lampworkers devised a variety of means to keep the wick in place and burning steadily and brightly. All lamps produced a "disagreeable," sooty flame, so ventilation systems — such as a hood venting to a window — are shown in various early texts, including Kunckel (fig. 4) and Smith (fig. 3).
In terms of basic materials, lampworkers from the 1600s to 1800s used a variety of glasses pulled into rods or tubes at the furnace or "glass house," as noted by Smith earlier. It was essential that these glasses have a low softening point. Diderot also describes using broken shards of colored glass or "enamels" to create flowers, figures, and beads.
While it is possible to soften some glasses in a candle or oil lamp flame enough to make very miniature pieces, adding oxygen rich air results in a hotter, more precisely controlled flame. By the beginning of the fifteenth century, glassblowers learned to force a narrow stream of air into the flame with a %%blowpipe%%. This increased the temperature enough to work and shape the glass. Figure 6 shows a candle flame altered by a blast of air from a fine jet, showing how the flame is projected in the direction of the blast. The jet may appear "like a tongue of fire" or "bushy" depending on the shape of the orifice, the strength of the current of air, and other factors.
Texts do not use the term "%%blowpipe%%" exclusively to refer to the hollow %%metal%% tube used for blowing glass at the furnace. The "mouth pipe" is often called a %%blowpipe%%, as is the tapered %%metal%% tube blowing air from the bellows into the lamp's flame. According to Danger, in order to "blow" the flame you must have a constant blast, usually created by one of three simple means:
- mouth-blower, or common %%blowpipe%% ... [where] the lungs are used as bellows, and the cheeks as an air-reservoir;
- foot-blower, from which the blast is created by air-pressure, caused by repeated strokes of a… bellows filling an… air reservoir;
- hand-blower, same as the foot blower, only smaller, placed upon the table instead of under it, and worked by hand instead of foot.
Henri Vigreaux, in 1930, reproduced an unidentified illustration of a woman using a mouth %%blowpipe%% while her hands manipulate a rod of glass in the flame. (fig. 7) "Originally, the %%blowpipe%% was only a simple, conical tube, more or less curved towards its point, and terminated by a very small circular opening,” explains Danger in 1831. He goes on to describe a special breathing technique used to keep a constant flow of fresh air to the flame, while softening and manipulating the glass simultaneously. Air held in the mouth and expelled into the %%blowpipe%% had less carbon dioxide than air expelled from the lungs. These low-tech, inexpensive mouth blowers, like the one in figure 8, were in use long after the introduction of bellows and even gas torches, particularly for beadmakers and artificial pearl makers, as well as amateur glassblowers.
For larger objects, using the bellows was preferred. The bellows was a device consisting of a flexible, sometimes valved, air chamber that is contracted and expanded (accordion-like) by pumping to force air out of a tube or %%blowpipe%%. Bellows attached to a lampworking table and driven by a foot pedal produced a strong, controlled stream of air that allowed the glassblowers to work hands-free in a much hotter flame.
In figure 9, Diderot illustrates "enamellers" or beadmakers' tables, including a view underneath the table showing the pipes carrying air from a central bellows to the four %%blowpipes%% and lamps. Also from Diderot, figure 5 shows the lamp with its %%blowpipe%% in operation, air running obliquely to the flame.
Manuals and Texts of the Day
Materials from the Rakow collection also show how extensively the books were disseminated. In this way, Danger's innovation, for example, became widely known and used. Books by Schreiber (1849), Pédroni (1849), and Tschenschner (1885) describe and illustrate Danger's improved lamp in their texts, together with the inventions of other inventors (fig. 11, 12, 13). The illustrations and instructions were copied from one text to another for years.
Over the years, in texts written for chemists and hobbyists learning lampworking, the older, less expensive methods persisted, while professional scientific glassblowers continually devised more advanced equipment. Blowpipe methods described earlier were in use well into the twentieth century, and as late as 1957 bellows were still being described as useful tools. Even the earliest lampworking manuals in the Rakow collection include directions for making a variety of chemical apparatus and ornamental designs.
If you are interested in learning more about early lampworking, the books discussed in this article plus additional materials are available for use at The Rakow Research Library of The Corning Museum of Glass, in Corning, New York.
I would like to give a special thank-you to Bradley Turner, Sally Prasch, Florian Knothe, and Robert Brill for their help in reviewing the material for this overview of the history of flameworking.
This article originally appeared in the Summer 2010 issue of The Flow and is reproduced here with the publication's permission.
Published on October 24, 2012