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Primer and topcoat


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I'm a rattle-can person when it comes to painting bodywork and I always leave a week or so between primer and top coats but I've often wondered just how soon you could put topcoat over primer.

For instance, on the automotive stuff I use it says to leave 15 minutes between coats. Now I take that to mean "coats of primer" if that's what I'm using or "coats of topcoat" if I'm spraying that. 

Would it be possible to wait 15 minutes after I've put my primer coats on and then shoot the topcoat in 15 minute intervals too? Would it be too much at once? Would it cause gassing out problems or possible reactions? 

With the rubbish weather in this country I'm looking for anything that can help make more use of any weather windows. 

Thanks for your attention gents. Looking forward to hearing your thoughts and experiences. 

Edited by Rockford
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What paint are you planning on using? I've done primer and top coat with Tamiya primer and paint all in one session, although it's usually a second primer coat after "block sanding" a first coat. I've never had any issues, and I let 15-30 minutes pass between primer and paint. 

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I usually give the parts a good look over after primer to make sure there are no more imperfections in the body work I may have missed. After I'm satisfied with that, then I put on the color coats, trying to stick pretty close to what it says on the can label.

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5 minutes ago, Snake45 said:

Only way to know is to test using the materials you'll be using. That's what plastic spoons are made for. 

Actually snake plastic spoons are made for eating. Sheesh thought everyone knew that ! 🤣

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Plastic spoons aren't a good test medium because, although they're made from polystyrene, their composition is chemically different from what kit manufacturers use. You will learn which paints and primers are compatible with plastic spoons; but, not for the various types of styrene kits are molded from. Use runners from parts trees from a specific kit instead.

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If you're using stuff like Duplicolor that dries really fast you can work pretty quick. I've gone from a bare body to a painted and cleared one in a day. I do two coats of Duplicolor white primer pretty close together and give them an hour to dry. Then I wet sand the primer with 1000 grit and set it aside to dry for another hour. Then it's two or three thin color coats, one about every 30 minutes. Then I let those dry for two or three hours then hit them with clear, either Mr Super Clear or Rustoleum Laquer. Finally I'll set that aside to cure for a week or so.

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I do it all in one day unless I need to sand the primer a lot to get out imperfections in fact all 3 in about 2 hours sometimes, many years ago when I was an automotive painter I had a rep tell me I could primer let it tack and put color right on it and it would chemical bond. Of course that was primer and color made to go together like if you were using all duplicolor or something like that.

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52 minutes ago, Ctmodeler said:

Actually snake plastic spoons are made for eating. Sheesh thought everyone knew that ! 🤣

I tried them once. They were brittle, didn't have much taste, and cut my gums. You can eat all of them you want, I'll continue to paint mine. :lol:

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32 minutes ago, SfanGoch said:

Plastic spoons aren't a good test medium because, although they're made from polystyrene, their composition is chemically different from what kit manufacturers use. You will learn which paints and primers are compatible with plastic spoons; but, not for the various types of styrene kits are molded from. Use runners from parts trees from a specific kit instead.

There might be something to what you say, but they're still good for paint-on-paint compatibility tests, drying times, and so forth. B)

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Although spoons are good for testing colors and paint compatibility I'm not sure that it is a fool proof way of testing recoat times. 

Different manufacturers specify recoat times. But I think you may get away with violating those times but it occasionally my go bad.

It would be safer to stick with one paint brand and type and follow that manufacturers reciat time recommendations.

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2 hours ago, Snake45 said:

I tried them once. They were brittle, didn't have much taste, and cut my gums. You can eat all of them you want, I'll continue to paint mine. :lol:

Lmao good one !!

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I know with alclads primer it doesn't take a very long time to be ready for top coat even for sanding.  I know with scale finish paint you can prime, paint, and clear in a day.  This all factors in with humidity and temp, but with a dehydrator it's all good.

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Most of the paint I use says you can handle in 20 min, re-coat in one hour, and cured in 24/48 hours.  I normally let primer set for 24 hours.  When I'm airbrushing acrylics I normally spray 5 coats and let it flash 20 min between coats.

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Well gents, as ever I'm impressed by your experience and willingness to help. Many thanks.

I took the advice and used primer and topcoat in the intervals mentioned by the manufacturer, 15 minutes before recoats, applying that to primer and topcoat. The finish is excellent with no adverse reactions and it has enabled me to get the job done in one day before the weather gets too cold or humid to be able to spray paint anything. It used to take me weeks to paint anything.

Once again, thanks for your help.  

IMG_20211022_141045193.jpg

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30 minutes ago, Rockford said:

Well gents, as ever I'm impressed by your experience and willingness to help. Many thanks.

I took the advice and used primer and topcoat in the intervals mentioned by the manufacturer, 15 minutes before recoats, applying that to primer and topcoat. The finish is excellent with no adverse reactions and it has enabled me to get the job done in one day before the weather gets too cold or humid to be able to spray paint anything. It used to take me weeks to paint anything.

Once again, thanks for your help.  

IMG_20211022_141045193.jpg

Looks good man.

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