Hmmm. i forget what is acceptable. I know someone will help you out soon enough though, check back daily :]
Side note not too off topic..
I've been using a glass tube.. i've cracked/broken a tube about 5 times now.. Its irritating..
I could really appreciate a metal tube for its durability..
BUT! Our bic lighter are made to handle isobutane fuel.. I've researched, and found both the shell, and inner casing to be made of polyacetal plastic.
Sooooo. Can we just make our tubes out of this plastic? who has got a red flag they can back up?
I see how keeping the column cold is a factor that helps. if we insulate the outside well, i feel that would solve any of those issues...
andddd, any red flags on the space craft aluminum?