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Glass Fusing Terms

Hey glass fusers, I have exciting news. I’m working hard on a new glass fusing eBook. There’s a lot of helpful information out there on glass fusing, and I’m thankful to the skilled artists who generously share their knowledge. But I thought, wouldn’t it be great to have updated information consolidated into one big comprehensive eBook? A single all-inclusive resource guide for glass fusers of all skill levels.

The following is an excerpt from my new eBook. The complete list is more comprehensive and considerably longer. Here I included the terms students ask about most. I hope you enjoy it.   

Anneal – Oceanside 96 – 960°F (516°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.

Note: Each family of fusing material has its own temperature range and recommended hold time. Consult the manufactures published guides for specifics.

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”. Oceanside 96 glass is “tested compatible,” that is, it has been formulated and tested for fusing compatibility, and is thus labeled. All products with the Oceanside 96 label are compatible with each other.

Color Shift: Some glass colors will “strike” change color, usually become darker when heated. This is especially true of reds, yellows, and oranges. It’s a good idea to test-fire small pieces so you’ll know what to expect.

Drape 1175°F – 1200°F (635°C – 649°C): In this process the glass is placed over the outside of a mold and heated until it falls loosely around the mold.

Embossing: To create an impression, pattern, or design on the backside of a fused glass project by fusing the assembled project on 1/8-inch-thick (3mm) fiber paper cutouts.

Firing Cycle: The specific set of times and temperatures a given project will experience during heating, annealing, and cooling in a kiln.

Firing Guide: This is a step-by-step schedule to fire glass of a certain size and thickness to achieve a specific result. 

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. 

Quick Cool: To open the kiln for the purpose of cooling the hot glass to prevent it from changing further. Always occurs above 1100°F (593°C) because glass is extremely sensitive to rapid temperature change below 1000°F (538°C). Also called “flash vent” or “rapid cool.”

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. 

Slumping Mold: Usually made of ceramic or stainless steel. Used to give the flat fused glass a 3-dimensioal shape or sculptural form. Most be primed before first use.

Soak: To hold the kiln temperature steady for a period of time. It allows the glass to slowly react to the heat and conform to the desired shape. 

Target Temperature: This is the temperature the glass will be taken to for a specific look or effect.

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 phased 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 slowly 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.  

Safety First: It’s important to note that the materials like glass and supplies like shelf paper that we put inside the kiln are special high-refractory materials designed to withstand excessive heat and are purchased at your art glass supplier specifically for kiln work.

Excerpt from the resource guide: Glass Fusing Terms by Lisa Vogt

Happy Fusing!


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Creative Slumping Webinar

June 2, 2022

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I’m back with my popular Webinar, Creative Slumping. In this detailed Webinar, I’ll reshape the way you slump and drape glass. See how thinking differently and using ready-made molds in new ways offers numerous and exciting opportunities to produce unique forms. You’ll also learn how to make your own graceful, free-form shaped molds from readily available materials with no laborious measuring or messy mixes needed.

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Downloadable instructional videos for every skill level.

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