wikiHow to Do Glass Fusing

Glass fusing is one of the oldest glass techniques on the planet dating before both glass blowing and stained glass. Traditional glass fusing is educational, fun and can produce beautiful results.


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    You will of course need glass. You can start with old bottles (don't mix different bottles together, use the glass from a single bottle). When purchasing new glass, be sure that all the pieces have the same Coefficient Of Expansion or COE. COE 90 glass is produced mainly by Bullseye and Uroboros glass studios both from Portland OR. COE 96 glass is mainly produced by Spectrum Glass works in Woodinville, WA, but Uroboros also produces some COE 96 glasses. Compatible glasses will be labeled with their COEs, they will cost more than regular window or stained glass. You will also need a glass cutter, running and grozing pliers, safety glasses, kiln wash powder, a ceramic kiln shelf, kiln posts, and a kiln or access to one. (Kiln note: Ceramic kilns can fire glass, they just aren't designed to do it well, so slow down the firing program)
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    Prepare your kiln and kiln shelf. This can be done by mixing up kiln wash (to the consistency of heavy cream) and painting it with a haike brush on the bottom of the kiln. Than you can thin it down to a milk like thickness and paint one side of the ceramic shelf with four thin layers. (Do not allow kiln wash to get on the elements of your kiln).
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    Determine your design and cut your glass. Remember that unlike stained glass you can stack your glass vertically.
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    Clean the glass to remove any grit and finger prints. (You can use rubbing alcohol, or warm soapy water. Do not use Windex or other commercially produced window / glass cleaners)
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    Place the glass pieces on the prepared kiln shelf. Keep your glass a bit in from the edge of the shelf depending on thickness your glass will grow as it is heated.
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    Close the kiln and start heating up your pieces. Depending on the amount of glass and the desired outcome, you will ramp up your kiln slowly. (Look up correct ramp times to avoid thermal shock your glass)
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    If desiring a tack fuse (where the individual glasses are connected but still have a separated look) the general temperature to obtain is around 1,325 °F (718 °C). If wanting a full fuse (where all the individual glasses have become one) , the target temperature is around 1,450 °F (790 °C).
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    If your items are small in size, you can usually turn off and unplug the kiln at this point and allow it to cool naturally. (If items are more than a half inch thick or wide, look up cooling times so as to avoid thermal shock).
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    Never open the lid of the kiln until your items are at least below 150 °F (66 °C).
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    It is always a good idea to take a simple class first before firing a kiln in your home. Classes can often be found at a local glass store, or community college.


  • COE means Coefficient Of Expansion. It refers to the change in linear size of a piece of material as it is heated or cooled. When working with glass you want a COE difference of 2 or less to prevent damage. For instance, two glass pieces with COEs of 90 and 92 work well, but 90 and 106 is not good. Pyrex is around 30, Moretti glass varies a lot, but is usually around 104, Bullseye makes 90 COE glass that is great for fusing.
  • More in depth info can be found at:


  • Use protective gloves if opening the kiln during firing. Kevlar® terry cloth gloves are ideal
  • Always unplug a kiln that is not is use.
  • If looking inside the kiln either by opening the lid, or looking in the peephole, always wear protective glasses. Kilns emit a LOT of infrared waves and you do NOT want to (literally) cook your eyeballs. Specialty glasses are made, welders goggles will do in a pinch.

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Categories: Glass and Stained Glass Projects