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Old 20th Nov 2015, 2:29 pm   #15
Phil G4SPZ
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Join Date: Apr 2005
Location: Bewdley, Worcestershire, UK.
Posts: 4,240
Default Re: Battery case links and scans.

I have been studying a couple of original British-made grid bias batteries and noted that they are sealed with conventional black pitch. Fortuitously I have just come by a small quantity of pitch, salvaged from a dismantled 1939 capacitor can which contained about 100 grams of the stuff, so last night I did an experiment. I melted the pitch gently in a metal dish over a gentle flame until it was a runny consistency, and did a trial pour by spooning the liquid pitch into a crude mould made from two layers of masking tape wrapped around a wooden block. The results were perfect.

Care is needed to melt the pitch without causing bubbles of gas to form, but other than that I was surprised how easy the process was.

Bitumen roofing compound, the sort used by felt roof installers, appears to have very similar properties and is available online in 10kg blocks for just £11.30. Such a quantity will last several lifetimes but is really inexpensive and would be sufficient to make hundreds of batteries. I'm tempted to buy it anyway, at least I'll never run out!

“The place where optimism most flourishes is the lunatic asylum” - Havelock Ellis
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