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--- projects:blinker:work_logs:2_window [2022/01/31 04:05] – tjhowse
+++ projects:blinker:work_logs:2_window [2022/02/17 02:24] (current) – tjhowse
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 ====== The window ======
 ===== The Plan =====
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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.
+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.
+===== The Video =====
+{{ youtube>HKjkeqgr-0Q?large }}
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