Devitrification

[Anonymous]

Sounds like devitrification (when glass starts to crystalize).  Glass meant for fusing is formulated to reduce this – though it still happens.  Stained glass generally “devits” more readily.

There are some commercial oversprays (also called devit sprays and overglazes) that may help.

Here’s a link to a recent discussion on fixing it after the fact.

https://fusedglass.wpengine.com/node/523

Make sure you are cleaning your glass well and spending as little time in the 1350° – 1400° F range as possible.

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Paul
FusedGlass.Org
Helios Kiln Glass Studio
PaulTarlow.com