Homebrew PCBs

mpdickens wrote:
> Epoxy has got to have heat to
> cure.

Then how do you explain when mixing a  < 1 gram of epoxy on the 
surface of a heavy steel plate that is at room temperature (15 ~ 
30\ufffdC) and it still cures relatively ok ? Any exothermic reaction 
will have nil effect in this situation.

There is a lot of info on epoxy here.
http://www.dow.com/epoxy/tech/index.htm

According to the document titled "DOW Liquid Epoxy Resins" it is 
the type of curing agent which determines the temperature and 
rate of cure. The aliphatic amines are the relatively fast room 
temperature type. There are others which require curing at 
elevated temperatures, which sounds like the type you once worked 
with. From what I gather from the document, the curing agents 
that need more heat and time give you a better cured epoxy resin, 
i.e. higher service temperature and more resistant to chemicals 
and solvents.