Great glass work is the product of a strong foundation and knowledge base. Let’s review common terms and make sure you’re equipped to produce consistent, high quality artwork.
C.O.E. – Coefficient of Expansion
C.O.E. – Coefficient of Expansion: This refers to the rate at which a specific family of fusing compatible materials expands and contracts when heated and cooled. Glasses must be of the same C.O.E. to be fusing “compatible”. Several manufacturers make fusing compatible glass, and each manufacturer has their own recommended temperatures to achieve specific results.
Compatible / Tested Compatible
Compatible: See also COE. Because glass expands and contracts when heated and cooled, glasses that are fused together must be “compatible” with each other. All of the glass used in a single project must be compatible to ensure a successful outcome. The glass must expand and contract at similar rates. If they are not compatible, stress-cracks or breakage will result.
Anneal
Anneal – Oceanside 96 COE- 950°F (510°C) 90 COE 900°F (482°C): Super heating glass, like we do in a kiln, creates stress in the glass. We alleviate the stress, anneal the glass, by holding it a specific temperature for a designated amount of time. How long is determined by the size and thickness of the project. The larger the project the longer the hold time.
Controller
Controller: This is an electronic device that automatically cycles the kiln through a pre-programmed series of segments of temperatures and times. They’re included on most medium sized and large glass fusing kilns.
Pyrometer
Pyrometer: A probe placed inside the kiln that measures the internal temperature of the kiln and shows the temperature on an external display.
Thermocouple
Thermocouple: A probe inside the kiln firing chamber that relays the temperature inside the kiln to the kiln controller.
Firing Guide
Firing Guide: This is a step-by-step schedule to fire glass of a certain size and thickness to achieve a specific result.
Firing Cycle
Firing Cycle: The specific set of times and temperatures a given project will experience during heating, annealing, and cooling in a kiln.
Segments
Segments: Firing guides are carried out in steps called segments. Larger, thicker projects usually have more conservative firing guides and therefore a greater number of segments.
Hold / Soak
Hold / Soak: At certain times during the firing process we hold, also sometimes called soak, the glass at a specific temperature for a designated amount of time to get the desired results.
Devitrification – Devit
Devitrification – Devit: The forming of crystals on the surface of previously shinny glass surface as a result of firing. The result is a distracting, inconsistent, blotchy or matte surface finish. Can also occur as a result of unsuccessful annealing or accidental heating to a high temperature. Can be caused by firing glass with fingerprints or other contaminants like cutter oil or glue present on the glass surface. Devit is more common when using 90 COE than 96 COE glass. How to prevent devit? Before firing clean the glass thoroughly, use a preventive spray available at your art glass supplier and consult the glass manufacturer’s firing guides.
Thermal Shock
Thermal Shock: Glass breakage do to rapid temperature change. Glass is sensitive to temperature change between room temperature and 1000°F (538°C) during the heating and cooling phase of the firing. To prevent thermal shock, we heat the glass slowly from room temperature to 1000°F (538°C). Once the glass and kiln are above 1000°F (538°C) the glass can be heated as fast as possible to the target temperature. When the desired result is achieved, the glass can be cooled as fast as possible down to 1000°F (538°C). At that point the glass is fragile and should be cooled slowly down to room temperature. How slow depends on the size and thickness of the project. Larger and thicker projects are fired slower than small projects. For example, a 4-inch square tile can be fired faster than a 12-inch square bowl.
Wherever you are in your artistic journey, you’re doing a great job!
Excerpt from the resource guide: Glass Fusing Terms by Lisa Vogt
Find the full Glass Fusing Terms Guide here.
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Happy Fusing!
Lisa
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May 28-31, 2024
YOU can make gallery quality fused glass art! You’ll love the personalized instruction in this exciting advanced technique, artistic awakening and skill building workshop. This is the turning point experience you’ve been waiting for.
Someday is here! What are you waiting for? You’re in your prime. You’re at the peak of your interest in glass fusing. Take the next step and raise your artwork to an exciting new level of sophistication.
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In this class, you will push the boundaries art glass imposes. Students will explore innovative approaches to design and combine multiple advanced techniques to construct original art that reflects their own personal style. You’ll enjoy: the one-on-one instruction, making multifaceted projects, the well-equipped classroom, and the intimate class size.
You’ll love the concentrated, in-depth study and creative momentum you’ll gain while actively producing, nonstop for four consecutive days. You’ll leave class with a working knowledge of kiln operation, custom project specific firing guides, and the inspiration you’ve been craving to go bigger and do more elaborate works of fused glass art!
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