by Doug Coulter » Mon Nov 15, 2010 10:36 am
Right, the liquid is very slow. Of course, when I find the leak, I do one of two things -- open it up and re-weld, or change liquid to shellac or glyptal and fix the leak! Glyptal is best for that, as it likes heat and thermosets for a pretty decent permanent fix. Shellac does too (the good "blond" stuff anyway) but won't take the higher temperatures as well...Either will just get sucked into a small leak and get hard before it makes it to inside the tank. Other sealants that work well would include most epoxies -- but if and only if they are mixed to a level of "thorough" that most people can't imagine, else you have this high vapor pressure resin or hardener left and that takes forever to finally get gone. Hysol 1-C seems about the best epoxy for vac systems, the solids are silicon dioxide in that, but some like JB weld too. The longer cure time ones seem better than the 5 min variety, probably because it takes >5 minutes of stirring to get epoxy mixed well enough.
(and you use from the middle of the mix puddle to avoid the poorly mixed edges).
I get hysol at mcmaster, glyptal at Caswell plating (its the real thing!), and shellac in flake form from woodworking supply houses. Zinsner "Bullseye" shellac from the hardware store is the good stuff too. I've used the flake shellac to mount windows over a hole in metal. Heat the window and metal up first, put on the shellac, lay on the window, heat further, then when it cools off, it's good and has just enough give to appease the tempco monster. It's permanent -- you can't re melt it and remove the window, as it thermo-sets.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.