projects:blinker:work_logs:2_window
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projects:blinker:work_logs:2_window [2022/01/26 05:08] – [The Doing] tjhowse | projects:blinker:work_logs:2_window [2022/02/17 02:24] (current) – tjhowse | ||
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====== The window ====== | ====== The window ====== | ||
===== The Plan ===== | ===== The Plan ===== | ||
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- | After the second firing. | + | After the second firing. |
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+ | I read that it was possible to harden glass by impregnating the surface with potassium. This is done in industry by immersion in a bath of molten salts. I have some potassium nitrate, so I filled a terracotta pot and buried the window inside and heated it up to 400°C for an hour. | ||
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+ | The potassium nitrate bath. | ||
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+ | The bath turned a foamy grotty brown. Molten potassium nitrate should be clear. I suspect the stuff I have is impure, or it attacked the glaze on the terracotta pot. I let the bath cool down and harden and then chipped out the window. The potassium nitrate was a filthy grey-brown and full of bubbles. After the glass cooled down I was gently hitting it with a hammer, to enjoy the noise. After a fairly gentle donk, no harder than I'd hit it before, it developed a small, barely visible circular fracture. I'm not sure if the potassium bath weakened it, or whether the temperature profile was a factor, or whether I just hit it in a different way. I wanted to empirically test the strength of this window, so I will re-fire it to fix the fracture and test it afterwards. | ||
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+ | Sources disagree on the proper temperature profile for potassium-toughening glass, but the general consensus seems to be over 400°C for many hours. If I try this again I will try to get some higher-purity potassium nitrate, and soak it at 425°C for 30 hours. | ||
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+ | ===== The Video ===== | ||
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+ | {{ youtube> | ||
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projects/blinker/work_logs/2_window.1643173708.txt.gz · Last modified: 2022/01/26 05:08 by tjhowse