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Old 2019-08-26, 10:02am
Robin Passovoy Robin Passovoy is offline
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Join Date: Dec 31, 2009
Posts: 495

COE stands for Coefficient of Expansion, and it's a measure of the hardness of the glass. The lower the COE, the less it expands or contracts, and the harder it is.
The higher the COE, the softer it is, and the more it expands or contracts.
Softer glass, such as 104 or 133 (soda lime and Satake glass) therefore melts faster and is runnier. Harder glass such as 90, 96, and 33 (Bullseye, Spectrum, and borosilicate) is much stiffer. All require different annealing temperatures that can vary somewhat if you're using regular or silver glass.
Most people start with softer glass, with 104 being the favorite, since the color range and ease of availability is the greatest, and it's easy to work.
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