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Friday, January 21, 2011

The Art of Studio Glass

Ancient glass pitcher, circa 2nd - 4th century CE.
Syro-Palestinian coast, possibly Sidon.
Image courtesy of Honolulu Academy of Art.

The origin of glass is unknown.  All that is known is that it began to be used very, very early in the history of humankind, and that it was highly valued from the start. Today, art glass is a respected and eminently collectible medium.  What follows is a very short and concise look at the types of art glass and the work of some extraordinary and impressive glass artists.

Glass sculpture "The Sun" by Dale Chihuly at Kew Gardens in London.
The sculpture is 13 feet high and made from 1,000 pieces.
Image courtesy of Wikipedia.

There is a distinction to be made between "art glass" and "glass art".  The term "glass art" typically refers to large modern works of glass that are usually one-of-a-kind and not meant to be utilitarian.  The image above is a good example of "glass art".

"Jamaica", fused & painted glass and frit by Raphael Schnepf.
This piece utilizes multiple methods of working with glass.

"Art glass" on the other hand, is glass that goes beyond its usefulness as a glass object and becomes a piece of art as well.   Another term often used is "studio glass".  These glass objects are intended to make a sculptural or decorative statement.  There are many ways of working with glass, usually differentiated as hot, warm, or cold glass.

 "Swan" kilnformed bowl by Linda Steider.
Ms. Steider uses powdered glass for a painterly effect.

Glass craftsmen are very cautious about using the same type of glass within a project, as different glasses have different COEs (Coefficient of Expansion), and care must be taken to avoid mixing glass with different COEs or the results could be disastrous.

"Donnie's Cat" kilnformed glass bowl by Linda Steider.

Cold working refers to working with glass that is in a cold state, such as stained glass.  The term "stained glass" originally referred to glass pieces which had been painted on, then heated or fused in a kiln.  Today it can refer to an object made of pieces of colored glass that are held together by lead came (thin strips of channeled lead) or copper foil, also called "leaded glass".

"Daniel" from Augsburg Cathedral,
early12th c., one of the oldest examples
in situ; image courtesy of Wikipedia.

Warm glass is kiln-formed glass, such as fusing, slumping, or casting.  One piece may use two or more of these processes.  When the glass is heated it becomes softer and less rigid, which allows its shape to be manipulated.  This is a slow process of working with glass, as care must be made when both heating and cooling the glass.

"Azure" fused glass bowl by Raphael Schnepf.

Fusing is using heat to join glass.  Tack fusing is attaching small pieces to a larger one, or assembling a large piece of glass from smaller ones.  When adding small pieces to a larger one, the project can be heated just enough to alter the form of the small pieces, causing them to melt and bind onto the larger one.  In full fusing, the temperature is higher causing the small pieces to be absorbed into the larger one, and the surface becomes flat.

"Triple Red Success" by Linda Steider.
The gold circles were hand drawn with 22k gold.

Slumping involves heating glass until it is soft and begins to sag.  Mold slumping is placing a piece of flat glass above a mold, usually made of ceramic.  As the glass heats, it "slumps" and takes the shape of the mold.  Care must be taken that the mold is covered by kiln wash, a wet, thick solution painted on kiln furniture and molds that prevents glass from sticking to them.  Free-fall slumping uses a form with a ring in the center.  Flat piece(s) of glass that are placed over the form will slump into it, forming a bowl or vase.  This technique is used to make vessals with steeper sides.  The kiln shelf underneath, covered with kiln wash, gives the piece a flat bottom.  A piece can also be draped over a mold. Draping usually results in uneven edges, although the pieces can be grinded to be more even, if so desired.

"Spring Bowl" fused glass server by Raphael Schnepf

If a glass piece is grinded, either to shape it or remove something that inadvertently stuck to it, it can be fire polished, which is heating the piece just enough to smooth and round the edges.  When the glass is still hot and in the kiln it can also be combed.  Combing forms a pattern on the surface with a pointed metal rake.

"3 Dancers" fused and combed glass plate by Raphael Schnepf.

Casting is when glass is heated to the point of being liquid and thus shapes itself to a mold.  The mold can be ceramic or a one-time plaster mold.  The glass can be billets, or loosely stacked pieces of glass, frit, and/or ground or powdered glass. Pâte de Verre (glass paste) is a mixture of powdered frit and a glue binder.  The paste is applied to a mold in a thin layer, and when fired forms a thin object.

"Oleander" pate de verre bowl by EM Studio Glass.
Click here to see her explanation of how it's done.

Hot glass is a process of forming glass objects in a direct source of heat.  The glass is manipulated with tools to shape it while it is molten, like pincers and shears. Lampworking and glassblowing are the main two methods.

"Peace Bead Set" by Marcy Lamberson.

Lampworking, also called flameworking or torchworking, uses a torch fueled by gas to melt rods and tubes of glass.  Once molten, the glass is shaped with tools. This method is used to create figurines, trinkets, curios, and beads.  There are two types of glass used:  soda-lime or "soft" glass; and borosilicate glass, called "hard glass".  Soft glass melts at lower temperatures, but expands more when hot and contracts more when cool, so it is prone to cracking.  Hard glass is more forgiving, but comes in fewer colors and is more expensive.  

"Sasha, the Diva Fish" by Marcy Lamberson.

"Bacon" by Marcy Lamberson.

"Wombat" by Marcy Lamberson.

Glassblowing is a technique that involves inflating molten glass into a bubble (called a parison) with the aid of a blowpipe or blow tube.  There are two major methods of glassblowing.  Free-blowing was first introduced in the 1st century BCE.  It is the process of blowing short puffs of air into a molten portion of glass that is gathered at one end of the blowpipe.  This forms an interior to the glob of molten glass which can then be inflated and worked into a shape.  A skilled glassblower rotates the pipe, swinging it and controlling the temperature while they are blowing into it.

The other technique is mold blowing, developed in the 1st century CE.  The glob of molten glass is placed on the end of the blowpipe where it is inflated into a carved mold.  Therefore the shape and texture of the piece is determined by the design of the interior of the mold, rather than the glassblower's skill.  Both techniques require working at very high temperatures, and some physical strength.

Pitcher by Alexandra Farnham
Vase by Alexandra Farnham
Black Glass vessels by Alexandra Farnham

Finally, there are glass artists who create by sandblasting.  This renders a sheet of glass translucent, transmitting light but allowing for privacy.  This involves the use of a special cabinet or room that allows one to blast a piece of glass with small, uniform particles in a carefully controlled atmosphere.  It can be used to make sculptural glass pieces or architectural features, like the doors below.

Sandblasted doors designed by EM Studio Glass.
The theme is Texas birds and trees, designed for a
private residence.  Click here to see process.
Detail of above door.

The objects shown may look doable, and I assure you they are.  After a LOT of practice.  Working with glass is very rewarding, but skills take time and effort.  As one glass artist I know said to a customer who asked how long it took to make the piece she was buying, "Two hours and seventeen years."

My thanks to the artists whose work they graciously allowed me to use:
Ellen Abbott from EM Glass Studio, Alexandra Farnham, 
Marcy Lamberson, Raphael Schnepf, and Linda Steider.
If you are interested in learning more about glass, I heartily recommend 
the Glass Craft and Bead Expo in Las Vegas.  This five-day, annual event 
offers classes in every aspect of glass art, even photographing and marketing it.  
There is a show during the last three days with exhibits from suppliers and artists.  
It is a great place to meet glass lovers from all over the world. 


  1. Thanks, Ellen, for allowing me to use your work! Your website is awesome!

  2. Love your articles Linda, thanks for including my work in this one!

  3. You described in a very good way the different between the two Glassblowing techniques in a simple way. Thank you for the information.

  4. Thank you for taking the time to comment!