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Building Tips and technical articles. => Paint and finishing => Topic started by: Allan Perret on February 27, 2012, 07:08:12 AM
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In current issue of Model Aviation, Bob Hunt writes about using Dupont Chroma Base for color coats and clear coat on his Crossfire Extreme. When talking about mixing the trim colors he mentions that there is no catalyst or hardner used, only reducer. He also mentions that it "air dries". I was under the impression that all coats in a basecoat/clearcoat system used a catalyst and cured by chemical reaction. So was I just mistaken about that, or is the ChromaBase product something different from a typical 2-part auto finishing product ?
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Allen,
no actually the typical base clear system uses an air dry base coat / color coat. In some of the older systems the reducer was an "activator" reducer, and did cause some form of catalyzation in the base coats. It was loaded with issues and the current systems use a non cured base coat. My understanding is that the top coat clear acts in some manner to cross-link the base when it is applied. That said, the system currently using no catalyzed base colors is very effective and quite simple to use compared to older technologies.
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I dearly LOVE the Dupont Chromabase/Chromaclear system! It takes so, much less paint! For the mint green I used on my Argus I mixed up 5 oz (including reducer). Had paint left and it covered completely plus it dried in minutes. DO NOT put any dope product over the basecoat, it will eat it right now. But dope (for repairs) WILL go over the clearcoat. That way I can use the system and silkspan for covering and still be able to patch any holes.
BIG Bear
RNMM/AMM
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Allen,
no actually the typical base clear system uses an air dry base coat / color coat. In some of the older systems the reducer was an "activator" reducer, and did cause some form of catalyzation in the base coats. It was loaded with issues and the current systems use a non cured base coat. My understanding is that the top coat clear acts in some manner to cross-link the base when it is applied. That said, the system currently using no catalyzed base colors is very effective and quite simple to use compared to older technologies.
OK, understand all that, but still confused. Bob Hunt mentioned how fast the color trim coats dry, and with no blushing.
So if there is no catalyst, the reducer must simply be some kind of solvent that has to evaporate for it too dry. If it air dries so fast why does it not have the same blushing issues of dope and lacquers ?
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Allen,
without going into a complex chemical explenation ( shich I dont think I could do effectivly anyway) simple answer, it just works,, Lacquer is an ancient technology material, this base clear system is fairly new and as such is much more advanced.
Trust me, blush is not an issue in anyway.
You are correct however in assuming that the thinner is basically a solvent , however there are many parts to the solvent, one gets the material to the proper viscocity to leave the gun, one gets the material to flow on the surface and yet another keeps the surface open to allow the trapped solvents to escape,, it is far more "engineered" than lacquer ever thought of being,, it works,
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Trust me, blush is not an issue in anyway.
I was not doubting you or Bob about the blushing, just did not understand why if the 2-part auto color coats dry (solvent evaporating) as fast as dope/lacquer does.
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I wish I could give you a better technical explanation, but I don't have one,, and I did not think you were doubting, I understood you were just trying to understand why,,
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Any need for a special respirator or air supply when spraying this?
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personally I recomend a proper respirator when spraying ANY material. so YES
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personally I recomend a proper respirator when spraying ANY material. so YES
ALWAYS wear a mask that filters vapors, with charcoal filters, etc..
BIG Bear
RNMM/AMM