Thread: ring tests
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Old 12-11-2016, 04:48 AM
Scott Benefield Scott Benefield is offline
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The ring tests that they do on Murano involve blowing a long bubble (with a wall thickness of no more than 1/16" and a diameter of around three inches) with the hot color to be tested gathered on top of the base clear glass. It is "cut" into a ring by wrapping a gather of hot glass around the middle of the bubble and popping it through thermal stress; then doing that again to make a ring of two or three inches. The ring is opened by laying another string of hot glass across one face. If done correctly, ring shouldn't have any annealing stress and should be thin and flexible enough to register any expansion mismatch between the glasses (i.e. opening up a gap or closing in on itself to make an overlap).

There are too many variables for that test to yield any quantifiable information--like measuring the gap to determine how much sand/soda to add/subtract--but it's immediately useful as a tool to visualize relative compatibility. Do you go forward with the day's production? Or did the batch person make a bad mix/melt? I'd say it's on the same order of usefulness as a pull test (thread test).
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