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Tips, Techniques, and Questions -- Technical questions or tips

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Old 2019-08-26, 9:51am
Cocteau2x Cocteau2x is offline
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Join Date: Aug 26, 2019
Posts: 1
Default COE as it relates to temperature and viscosity

I have a few questions about glass COE/Temperature/Viscosity ...

Does LOWER COE mean ...
LOWER Viscosity (moves slower)
and Higher (or LOWER) temperature to work with?

I am sorry if this has been asked 1,000's of times here before.
(This is my first post ... and have not found the "search function yet")

Thank You
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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: 504

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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Old 2019-08-26, 4:42pm
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Speedslug Speedslug is offline
Join Date: Mar 21, 2009
Location: Winnebago, MN
Posts: 2,477

I will add that transparent glass is often stiffer than opaque glass of the same class of coe.

With the exception of Double Helix brand clears like Zepher. It is very clear but it melts like butter.
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Old 2019-09-16, 2:08pm
5betsy 5betsy is offline
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Join Date: Apr 17, 2009
Location: Back in Tucson for good
Posts: 354

There have been a couple very thorough discussions of viscosity and Coe both here on LE and over on Wetcanvas. I find searching inside both sites frustrating so I use Google.

Try using search term 'lampworketc viscosity' and both threads pop up.
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