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Originally Posted by ProdigyCustoms
Yeah, I really appreciate you guy's agreeing with him also. I am hoping that some day I may know enough to do this for a living too. For now I will just continue to sit in class and take notes before I attempt to do this professionally. There seems to be so much to learn. The part I do not understand is the 3 week outgas stuff. I also do not understand, Are you saying it is a chemical process or evaporation process Evil? I notice in your first introduction post you refer to a chemical drying process, then just above you say "it seems a misconception by a lot of folk that 2K "cures" chemically", which is confusing the hell out of me?
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Hi sorry for any confusion,if you re read my posting you'll see that it says.... "it seems a misconception by a lot of folk that 2K cures chemically & they aren't aware of the need to avoid solvent trapping".....Yes it does "cure" chemically but also by evaporation & the point I was trying to make was that most people aren't aware of the fact that evaporation also takes place & care has to be taken not to trap solvents, people think it just "cures" & that's it! I guess it's just that painters use words in their everyday speak that can be taken outta context if used literally.I get a lot of this when I take college class. The easiest way to try to explain this is:-......... before the invention of 2K paints, all paints had to have a thinners in them to reduce the viscosity (thickness) enough to allow it to spray outta the gun. Once the paint was sprayed it would take a while for it to dry or "cure" (cure is a word used but it doesn't cure in the true sense of the word, it's a painters way of saying dry
).The thinners in the paint would evaporate to the paint surface,which enabled the paint to dry. Drying times would vary dramatically between various products, so I'm unable to give specific times here.These paints are known as single pack type paints,cellulose, eurethane, lacquer or synthetic, all are air dry.
2k Paints or 2 pack paints, have a thinners & a catalyst, the catalyst speeds up the drying time dramatically, & the thinners is there to allow the paint to be sprayed outta the gun. Now this is where it can get confusing, yes, the catalyst does have a chemical interaction with the paint which allows the paint to dry quicker, but the solvents or chemicals in the catalyst need to evaporate.The thinners also interacts with the paint to allow it to dry (evaporation) so I guess if you really want to pick the bones out of it, both chemical & evaporation occur in the drying process not one on it's own. You can actually spray 2K without catalyst & it will airdry slowly & be able to be cut back & polished.The smell of a fresh paintjob is the chemicals/solvents evaporating & not the smell of the paint itself. Now to add more confusion,... the thinners you get to go into 2K comes in three types, slow standard & fast, which will speed up or slow down the drying time accordingly.Slow & standard can be used in a bake oven & the fast would be used for small blow ins or for a non bake situation where it dries in atmosphere without the addition of heat. So you see, the thinners affects the drying time also, which shows evaporation takes place
There are an awful lot of chemicals in the catalyst or hardener as it's known, the worst being Isocynates (cyanide based) which can kill you & cause cancer if you don't use proper air fed masks when spraying.Once the paint has been sprayed onto the panel the catalyst speeds up the drying time dramatically, but there are still solvents in the thinners & catalyst which need to be released to the paint surface. 2K paints surface harden very quickly & with the normal amount of paint sprayed ie 2-3 coats, there's never a problem with solvent entrapment (or outgassing as it's known professionally, solvents evaporating to the surface). It's only a problem if the solvents aren't given sufficient time between coats (flash off time) or if too much paint is applied. If this is the case, the solvents aren't able to get to the surface before the surface "cures/dries" & the solvents become trapped. When trapped they can be seen as very small white dots when looked at closely in the paint.With solid colour you'd be hard pressed to see them, but in a clear coat over a black or dark colour they become very visible.Obviously there's far more to it but hopefully I've explained the basics of what goes on. As I said, painters get into the habit of using words & phrases when talking to each other about what they're doing & if used literally can confuse others.I realise that maybe this stuff should have gone on the tech discussion pages, sorry 'bout that. Hope this has helped to answer your questions.
