Well honestly I have never tried an alumimum pot because the original instructions I got from my sicence teacher told us not to. (this is the same guy that walked us step by step through the process of manufacturing nitroglycerin... But I'm NOT sharing THAT secret
) Anyway it could be one of several reasons:
#1 Alumimum pots tend to heat up MUCH faster and thus make you smoke bomb intoa smoking mess.
#2 Alumimum might react with salt peter and make some kind of poisonous gas of some sort.
#3 Some other nasting thing.
Anyway obvously if the answer were #2 (or #3) then I suggest following my old teachers advice and NOT using the alumimum. (would you realy want to take the risk anyway? Corningwear isn;t that expensive
)
Oh and just FYI my memory was a little sketchy on the exact details of this formula from school (it's been a LONG time since I've graduated) so this formula is a mixture of three things:
#1 My (sometimes failing) memory.
#2 Trial and error
#3 Research on a bunch of "ghetto" "do it yourself" paintball pages.
Anyway final word:
Follow the directions to the LETTER (or risk making a BIG mess and possably making somthing poisonous) and use at your own risk.