Getting to Know Boro

History of Borosilicate• Developed by Freidrich Otto Schott

– German chemist and glass technologist• Migrated to U.S. by Schott employees who joined Corning

which led to making Pyrex in 1915• Comprised mainly of 80% silica and 13% boron

– Melts at a higher temperature and has a shorter working time– Less dense than soda lime which makes it more durable

• Primarily used for lab ware or applications where resistance to acids and heat are important– Glass of choice for pipe-making industry

History (cont’d)• John Burton (johnburtonglass.com)

– Developed formulas for hand- mixed striking colors- Glass - Hand Blown, SculpturedAnd Colored: Philosophy and Method

• Bob Snodgrass (snodgrass.net)– Father of Fuming– Color adoption through fuming techniques

• Preforms (Borostix)– Used as semi-conductors (cathode gunmounts in color TVs)– By 1997 there were 2 dozen colors

History (cont’d)

• Glass Alchemy introduced “crayon” series in 2000– Required outside-of-the-box thinking to develop– Glass is produced in small pots or crucibles that

hold 50 pounds of color• 200-400 pounds per year

– Beginning of the 33 COE Glass Revolution

Boro Manufactuers• Glass Alchemy (glassalchemy.com)

– Family business started in 2000– Rod, frit, and tubing

• Momka (momkasglass.com)– 37 years– Sofia Bulgaria– Rod

• Trautman Art Glass (taglass.com)– Mid-1980s by Paul Trautman– World’s first commercial operation (Northstar)– Sold Northstar in 2002– Rod (also manufactures reactive soft glass)

• Northstar (northstarglass.com)– Founded in 1980– Rod, frit, and tubing– Users manual on Wale Apparatus available for download

How to Work with Boro

• Always work with a neutral flame– Helps maintain consistency and vibrancy– Eliminates cracking of chrome colors– Save reduction for the final step

• No flame will be neutral from base to tip– All torches have a different neutral zone– Area closest to torch face tends to be reducing –

do not work close!– Always work mid-flame

How to Test for Neutral Flame• Heat a rod heavy with silver

until it glows a dull orange; remove from flame and cool– Does not appear to change

color – you have a neutral flame

– Light sky blue or metallic sheen – reduction flame so propane needs to be decreased

Understanding Striking

• Any color change in the glass due to heat treatment– Copper and silver glasses have different reactions– Crystal growth• Function of time and temperature

• In torch flame or kiln• Leave in kiln– Several annealing runs can change color

Polychromatic Colors

• Silver-based formulations– Worked at hot temps to create, form and

assemble the elements– Anneal at 1075 to 1125 degrees F• Allows growth of crystals

• Growth process– Orange, ruby red, red-purple, purple, blue then

green

Polychromatic Colors (cont’d)• Core temp drop and reheat only surface– Silver crystals grow faster in the top layer

• Uneven heat– Creates a “veil” of color (or haze)– Haze needs to be removed because it will mask beauty of the

color• Create different patterns– Twisting rod– Cool paddle– Pinch with pliers– Clear frit

Polychromatic Colors (cont’d)

• Luster to surface– Heat to 1200-1250 for 20 seconds• Neutral – luster will be silver• Bushy – luster will be multi-colored

• Polish to enhance brightness• Not all colors are created equal

Torch Size and Type for Boro• Factors to consider

– Size of torch– Surface-mix* (gases mix outside of torch) or pre-mix (gases mix

inside of torch)– What you are making

• Cost and Long term needs• 10 psi propane, 10psi - 20psi oxygen

– Smaller torches run at half• Concentrator or Tank

– 5 LPM (liters per minute) for boro– Desired results will affect decision

Pro and Cons• Pro’s

– Not as susceptible to cracking problems even when cooled quickly without kilning

– Rod of glass can be directly inserted into heat without having to be slowly warmed

– Can be used for large sculptures in which a small section can be worked without the entire piece being hot

– Can be reheated and reworked– Better for blown work

• Con’s– Very few “crayon” or WYSIWYG colors like soft glass– Individual colors can be expensive– Torch and oxygen may need to be upgraded

Resources

• A Beginner’s Guide to Glass Alchemy Colored Borosilicate by Drew Fritts (frittsartglass.com/marbles/articles/Borosilicate.pdf)

• Northstar Glassworks (www.northstarglass.com)– User’s Manual (copy online at Yahoo group page)

• Glass Alchemy– List of colors on website have working tips for each color

• The Melting Pot (www.talkglass.com)• Glassline Magazine forum (www.glassline.net)• Lampwork etc.

Boro is Glass!