Fusing Glass COE And Its Effect On
Fused Glass Outcomes

Fusing glass may break or crack if fused in a glass kiln with glass from another maker due to COE differences.

There are a number of makers of fusing glass producing a range of colors & styles. Two of the more popular brands are Bullseye (COE 90) & Spectrum Glass known as System 96 (COE 96).

These and other brands are used to produce fused glass jewelry as well as glass art pieces.

However these two brands cannot be fused together as they are not compatible due to the different COE (co-efficient of expansion) of each brand.

COE is a measurement of the rate at which glass expands and contracts during a heating and cooling cycle.

You can find the details of glass compatibility testing here.



Combining COE 90 and COE 96 in the same kiln formed item will most likely result in either cracking or breaking of the piece.

Both these makers produce fusible glass that is known as tested compatible. This means that Bullseye glass COE 90 is compatible with other COE 90 fusing glass in the Bullseye range.

Spectrum "System 96" is tested compatible with COE 96 glass in the Spectrum range.

The Uroboros Glass Studios produce a range of glass which is tested compatible with Bullseye COE 90. They also produce glass which is compatible with Spectrum "System 96".

When purchasing these brands look for the "Tested Compatible" sticker which is affixed to the glass by the maker.

If you purchase COE 90 and COE 96 always keep them apart in your studio so as not to mix them up in your fusing projects.

Dichroic glass is also produced in COE 90 & COE 96 & the same rules apply about not fusing different COE’s together.

Other manufacturers also produce glass with differing COE’s, the same rules apply whether it be COE 90 or COE 104.

Coe 104 Moretti sheet glass is available in a limited range of colors and fuses at 720 C and slumps at 620 C.

There may be differences in sheets from separate batches. Users report some devitrification problems.

Whatever brand of glass you use is a matter of personal choice, all are suitable for kiln formed jewelry.

These makers produce a wide color range of glass with solid and transparent colors available.

The same colors & COE are produced for thin glass, stringers and rods as well as crushed glass (frit) and glass powders and glass confetti (fine glass shards).

Bullseye Glass has a large range of fusible glass,fusing supplies and technical information.

Spectrum glass also has a large supply of fusible glass, technical information and fusing patterns.

Bullseye have a great printed catalog that covers their product range. A catalog request form is available on the Bullseye website.



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