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Re: Re: Need Advice About Constructing Vacuum Coating System

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Posted by Tom Leech on December 21, 2000 02:05:04 UTC

hi stephen, i am no expert on this, but have considered doing it myself sometime. first, a note about safety. you plan to cut the bottom off a huge jug, grind the edge flat, and use it as a bell jar. this frightens me a bit, because not knowing the particulars of the jug, i wory about implosion from external pressure. if you are successfull in proceeding with this keep your distance, unless you know just what is going on. i once had a 1 gallon jug explode on me once when i was doing foolish things. i also used to design submarines and submersibles which are subject to external pressure. anyway, take care. second, scientific supply houses carry "vacuum grease" which is used at most all joints, and does not off gass. scientific supply houses also supply t stage "hi vac" pumps which will pull you down to 1/10 micron of mercury pressure. thats damn low, and i have heard that it is low enough to do coating, unless you are a professional in the business, in which case a diffusion pump in the system is taken for granted. these things come up on www.ebay.com. just type in vacuum pump, today there are 58. none that is as described above (scientific supply house "hi-vac"). that is all that i know on the subject. tom leech

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