There are two epoxy systems available to us, polyamide and polyamine. The polyamine systems will react/mix with a little moisture in the air and forms amine blush slime layer as a function of cross linking. The polyamide system manages to crosslink without is side effect. An example of ideal application is underwater epoxies, amine epoxies react with the water and are not suitable.
I was a strong fan of the West system, used it for yrs, had difficulty in finding it, local stores switched to MAS. I was quite vocal about not liking the change until I tried it. To gel coat over it still requires proper surface prep, just less amine blush to worry about. MAS is an amine based epoxy, Ive used the slow and medium hardeners without experiencing any blush. (They do market it as blush free)
Blush is a reaction of moisture and carbon-dioxide in the atmosphere with the hydroscopic nature of the " simple amine" compounds due to excessive free radicals that are present during the reaction/ curing process. (very common in the lower end epoxies) Cycloaliphatic diamines / Cycloaliphatic Amines are almost completely void of the free radicals that hydroscopicly react making them inherently the most stable to not forming "salts of amine carbonate" aka, blush, but this comes with a higher price tag. Another down side is that they have difficulty in being reactive at low temperatures.
Be wary of those that try to appear larger than life by attempting to make everyone around them appear smaller.
Cal 9.2 #19 SilverSwan
Last edited by roline; 11-03-2009 at 06:25 AM.