The Art of Glassblowing

What is glass?Glass is typically made from three types of materials: Formers, Flues, and Stabilizers. •Formers are the main ingredients, making up the largest portion of the mixture. The silica found in sand or quartz is the most common former. •Fluxes lower the temperatures at which the former will melt. Soda ash and potash are the common fluxes. •Stabilizers combine with the formers and fluxes to keep the finished glass from crumbling or falling apart. Calcium carbonate is the most frequently used stabilizers.

Properties of Glass• Mechanical-Glass is strong and hard but elastic.• Chemical – It is corrosion resistant, meaning that it is

affected by few chemicals and resists most acids. • Thermal – Modified glass can withstand intense heat and

retains it rather than conduct it. • Optical – It can reflect, bend, transmit and absorb light. • Electrical – Glass strongly resists electric current and it

stores electricity efficiently.

Batch• These three ingredients are mixed together

in a tank and heated at a high temperature until the mixture reaches the consistency of honey.

• This mixture is called a batch.

• At this point, the molten glass can be cast, blown or shaped.

FORMULAFormer (sand)

+ Flux (ash)

+ Stabilizer (calcium carbonate)

+ Heat (2100-2300F)

= Batch of Glass

+ Metal Oxide

(for color)

How is Glass Colored?• The previous formula creates clear glass. • To make colored glass, metal oxides must be added to

the batch. The following oxides produce the following colors: – Copper = Turquoise– Chrome = Green– Cobalt = Blue– Cadmium & Gold = Ruby Red

Process1. The glass blower first picks up a gather of glass on the end of his

metal blowpipe. 2. With the gather of glass on the end of his blowpipe the glassblower

blows in the opposite end of the tube and forms a bubble of air in the gather.

3. The craftsman turns the blowpipe while blowing to help keep the developing form symmetrical.

4. If the glass becomes too cool to work with the piece is reheated in another furnace called a gloryhole. The glass can also be reheated using a blowtorch.

5. The glassblower continues to blow on the pipe as he or she fully develops the form of the piece.

Tools• A variety of tools and processes can be used in the development of blown glass.• Marvering is the process of rounding and evening out the form using a marvering

table or paddles. • When the lip or open end of the piece needs to be developed, the glass is

transferred to a pontil rod. This tool is attached to the bottom of the glass which is then removed from the blowpipe. Now the lip is free to be shaped and decorated.

• Tools such as shears, pliers and forceps can be used to cut, bend and stretch the glass as needed.

• A rim, foot, handle, spout, etc. can be fused onto the main piece using other glass pieces.

• When the creation is completed, it needs to cool slowly to avoid thermal shock. This is done in an annealing furnace.