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Hi Big Jim, No such thing as stupid questions. Just stupid answers :o). Hardeners, sometimes referred to as activators or catalysts, when added to paint, cause the paint to cure by chemical reaction rather than by oxidation in air. Curing is separate and distinct from drying, e.g. a paint film can be dry to the touch but uncured. When you mix the hardener with the paint, there is what is called a "pot life", after which time the mixture becomes unusable. This period varies with the exact products but typically is a matter of a few hours at best. I have used a primer surfacer that has a one hour pot life! If you let mixed material set overnight, it will likely be similar to jello (or worse) in the morning. If you don't clean your spraying equipment soon after use, you can have a significant problem on your hands with cured or semi-cured material in the internal passages. Typically enamels or urethanes with hardeners are applied with only a few minutes (say 10 or 15) between coats. The first coat will not be dry to the touch before the second coat is applied. In any event, you should follow the specific instructions of the paint manufacturer. Hardeners also have a shelf life after opening which should be adhered to for best results. If the hardener you have is more than a few weeks old and has been opened before, you might want to consider using fresh material instead. I am not a believer in mixing and matching different materials between different manufacturers because of the proprietary chemistries involved. Unless you have a specific combination that you know, by experience, has been satisfactory, I would recommend you follow the instructions of the paint manufacturer to a tee. Otherwise, you may be disapointed in the results. A word of caution: Paint hardeners contain very toxic materials called isocyanates. I do not recommend using them at all unless you have the proper respiratory protection. Proper, in this instance, means a respirator that has fresh air continuously supplied to the facepiece (or hood). Chemical cartridge respirators are not considered adequate for these materials. Eye and skin protection is also advisable. Read all the fine print on the hardener label and follow it. They do not print the warning "...for application only by professional trained personnel...not intended for sale to the general public" on the can for nothing. Be safe. Rod
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