Paint drying time before masking

[Doug in NJ]

Hello,

During the last week I painted two of my doors, with PPG Concept. I sprayed the main color, and about 20 hours later I masked off the upper portion and the window reveals, and sprayed the upper part. It was a bit cool at the time, about 60 to 65 degrees. When I removed the masking tape, I saw that it had left an impression on the first coat, a slightly rough area that sort of looked like tape adhesive residue, but would not come off with prep-sol.

So I am wondering: How long are you supposed to wait before masking over a fresh coat of paint? If you wait too long, the second coat might not adhere properly to the first coat.

It wasn't a disaster, like I feared at first. A light buffing should remove all traces of the tape marks.

Doug

[peters180a/170b]

That's why i pick 1 color for the whole car with no reveals.[L.O.L.] When i did do two tone i used ["FINE LINE TAPE , 3M tape]. The problem was you left the tape on to long.The paint cures longer so you can wait atleast 1 week before two tone.If you don't get the hardener right on a single stage ,mixing ratio must be correct .Get a measuring cup. Other then that .take your time.] and wait till the weather in warmer. GOOD LUCK ,peter180a

[BRENT in 10-uh-C]

Doug, a couple things comes to mind. First off, we tape after 6-8 hours on non-force dried paint, and after an hour or so (as soon as cool to touch) with force dried so I am guessing a couple of things might have contributed to this. Generally, we would have started with an 860 reducer followed by DT870 once the first coat was applied and flashed. If you use 870 or hotter thinner and did not have adequate air flow over the topcoat, it may have still been releasing solvents which caused the printing. Nothing wrong with this as it generally allows the surface to flow out more with no adverse effects. The next thought might be that the hardener (DCX61) was getting old or you used the wrong hardener (i.e DU or DFX), --or the tape was not a low-adhesion tape. It sounds as if it only affected the topcoat anyway and by the time you cut & buff, you'll never see it.

With regard to the second coat time over the first coat, generally the longer you wait, the better it will do. We generally wait 10-15 minutes between coats but you could go 1 hours between coats and it will still stick because you have an 8 hour recoat time. When aplying your secondary color, you need to always scuff it with 600g to create a mechanical bond so you don't need to work about hotting within your recoat window.

[edzaha]

Also watch what kind of tape you use some adhesives just don't work well for this. Spend the extra$ and get the 3m blue painters tape I have not had that problem with it.

[Doug in NJ]

Thanks for all the advice. I had used the narrow 3M fine line tape for masking the border of the window reveals, plus low-tack blue painter's tape for the rest of the reveal area. I suspect my can of DCX61 is getting too old. I'll use a fresh can the next time I paint something and see what difference it makes. (BTW, I used DX860.)

One question about scuffing the primary color before applying the secondary: How can you do this without messing up the masking tape? Do you simply work as close as you can to the tape, and not worry about the last 1/16" or so being un-scuffed?

Thanks again,
Doug

[Doug in NJ]

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During the last year or two, while i was wondering about the right way to do the two-tone paint job, I often started wishing I had decided to just go with solid black, like the car was originally.

But after I'm done, I'll probably forget about the extra work (and cost), and be happy with the handsome paint job...

Doug

[BRENT in 10-uh-C]

Doug, always sand everything that is going to be painted. Use your fine-line to define the edge, next sand all the areas inside up to ¼" or so from the tape with 500-600 grit ...then come back over the tape with a gray ScotchBrite to scuff that. Just rub over the top of the tape. That's all there is too it.