Hopefully I am going to be spraying some Omni MP182 primer surfacer this weekend. I bought the primer last fall when the temps were cooler and they sold me fast hardener and reducer to go along with the primer. Now that the temps are in the high 70s to low 80s, will that fast hardener work ok or do I need to get some slow hardener?

I am assuming that fast hardener dries/cures quicker than slow... is this correct? What are the temp ranges for the two different products? What kind of negative effects would I see if I used the wrong product for the temperature?

Thanks in advance guys!

Your fast reducer is made for cold weather as it dries faster. But in fact a fast reducer can increase the dry time as the top skims over sealing the solvents in.

Negative effects would be pinholes, shrinkage, loss of gloss caused by the fast reducer. You need to get the proper reducer for the temps.

I'm certainly no expert but the SPI Web site says to use the slowest possible reducer for best results. Not sure if this would apply to all manufacturers though...

Yes, it does. The slower it is, the better solvents are released.

I went to the paint store today to get some slow hardener, they dont stock and said they always sell it with the fast hardener. The guy said the only thing I would have to do different in higher temps is make sure I let it flash about 10 minutes before another coat goes on so that the solvent would have time to escape.

You have to let everything flash between coats, no matter what, clear, base, primer, etc. The problem with fast reducer, in high temps, is that it will flash too fast, and trap in the solvents, where a slow reducer won't flash as fast allowing all the solvents to escape before the "skin" develops.

Personally, I would be looking for a new paint supplier if mine ever gave me that information...