Glass Art Techniques                                                              Education Page

by Alison Ruzsa & Sami Harawi                                                                                                                 June 2005

Glass is an art medium with seemingly endless technical versatility
 and a rich, long history. Basic elements of sand and soda lime are
 combined with coloring agents, then melted together to produce the
 raw material. The raw (soft) glass prepared in Murano, Italy,  has a
 great reputation anchored in centuries of appreciation for its high
quality. Although this well deserved reputation persists today, good
quality glass is produced elsewhere, particularly in the United States
 (Corning, Bullís Eye and Schott glass).

Read the rest of the 2005 Text through the following link:  Glass Art Techniques


Below is the Text written for the 1998 Exhibit, The ABC of American Glass

Glass Blowing goes few millenniums back, at least to the early Egyptian Civilization. Although glass blowing has reached a high sophistication level, very little about the technique itself has changed. Basic elements of sand, soda lime, are combined with coloring agents, and melted together to produce the raw material.

To create a blown glass object, the molten glass is "gathered" from the furnace on the end of a long hollow metal "blowpipe". At this stage the glass is typically around 2100 degrees (Fahrenheit), and has the consistency of honey (it "freezes" at around 900 degrees). The glassblower introduces air into the center of the gather through the blowpipe. A variety of tools are then used to shape the glass to form. As the glass cools it begins to stiffen and must be reheated to allow continuous shaping and reshaping. The glassblower uses a smaller furnace, the "glory hole" (because of its bright glow) for the re-heats. These re-heats allow the artist to work on a piece for a long period of time, shaping and blowing until the desired result is achieved.

When the piece is finished, it is placed in an oven (kiln) for annealing. Annealing is the process of slowly cooling the glass to room temperature to stabilize its delicate crystalline structure. If the piece is heated or frozen quickly, it will crack. Annealing is not only used for blown glass, but is done for the pieces produced from most of the other techniques described below.

Hot Sculpting denotes a technique in which glass is gathered from the furnace on the end of a solid metal rod (puntil) and shaped with tools into a Sculpture. Although the set up is essentially similar to that for blown glass, no actual blowing takes place.

Cast Glass may predate blown glass. There are examples of Ancient Egyptians experiments with this technique. They used "cold core casting" in which the glass was applied to the outside of a mold. A variety of techniques for casting glass are widely used today. Pate de Verre, (French for paste of glass) and Kiln Casting are essentially similar. Both involve filling a mold with cold glass heated it in a kiln till the glass fuses together at the melting point. In Pate de Verre the glass is crushed into a fine paste before it is put in the mold; for Kiln Casting, larger chunks of glass are used.

In Hot Casting, glass is heated at a temperature higher than for Glass Blowing (2350 degrees Fahrenheit). It is scooped out of the furnace with large ladles and poured directly into the mold. Intricate molds are made of ceramic and silica, materials that will withstand the heat.

Sand Casting is an ancient technique still in use. It involves creating a mold by depressing objects into silica sand, (which is mixed with a binder and or injected with C02 to make it hard). Molten glass is poured into the mold.

Cold Working refer to methods that are work glass in it’s "frozen state". It includes Sandblasting, Engraving, Cutting, Grinding, and Polishing. Bonding the glass together with specialized glues is also part of Cold Working. Each of these techniques allows by itself an array of possibilities in Art Glass. Cold Work often results in pure geometric forms. Some artists consider the cold work as an extension of their "hot work". But most Cold Work artists use glass that was produced for their needs in specialized places in the US and in Europe. Dichroic glass is often used in Cold Work sculptures.

Lamp working is a method of manipulating small rods and tubes of glass in the flame of a torch. Its origin is vague and disputed, but experts agree that initially the glass was heated over small oil burning ‘lamps", hence the name Lamp working.

In the fifteenth century soft glass was developed by A. Moretti to melt at lower temperatures in order to accommodate this technique. It was used to make small-scale sculptures, and glassware without the overhead expense of traditional glassblowing. Soft glass is still produced by the same Muranese family. Today, Lamp workers use it to create unique works of art with torches that burn gas and propane and can produce a much higher temperature, and a larger flame.

Some artists as well as glassblowers of scientific glassware, use a glass made of a borosilicate base, which was developed in the US in the 20th century by Corning. It can withstand higher and more drastic temperature changes without cracking or boiling.

Stained glass is an art form that is was developed in the 9th Century in Central Europe. Originally, sheet glass was cut from large "roundels" (a method of blown glass in which the final form is spun out into a large round plate). Metallic oxides (for coloring) were applied to the surface of the glass and then heated in large kilns. These pieces of "stained" glass were cut and assembled, using strips of lead, into larger compositions, which not only provided light but also became a major architectural design element. They were predominantly used as pictorial themes in cathedrals.

Today, artists continue using stained for windows with traditional and contemporary designs and in both religious and secular set-ups. However, some artists have taken stained glass outside and beyond the windows into sculptural forms, architectural and figurative.

Slumping and Fusing techniques use flat pieces of (usually stained) glass. In the Fusing technique, multiple glass pieces are arranged in a pattern and heated in a kiln to be fused as one piece. In Slumping, the glass is laid into, or on top of a mold and heated just to the point where it "slumps" to fit the form of the mold. Once the glass reaches the desired form it must be cooled quickly enough to stop the movement that will result in cracking. Although these methods sound simple, the objects created are quite often very intricate in their design, and hours of painstaking labor may go into the arrangement of the glass. In many examples the glass has been fused into a pattern and then slumped to fit a particular form.

Neon is a method developed at the beginning of the 20th century, mainly for commercial use, but made its way into the art world as well. In this method, the glass is mass-produced into long tubes, which are then bent and spliced together with a torch to create the desired forms. Once the form is complete electrodes are spliced onto the two ends of the piece and a vacuum pump removes air and impurities from the chamber. A rare gas such as Neon is introduced into the chamber before it is sealed off. When attached to a transformer the electrodes excite the atmosphere in the chamber causing the neon to glow a deep red color. Other rare gases such as Argon and Krypton, are used to produce other colors. Combining this with tubes that are made of colored glass a large palate of bright hues is achievable.