Abandoning Plastic Film for Paper

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PostPosted: Wed Oct 20, 2021 1:38 pm
Does anyone have any suggestions regarding preparation for the next attempt?
I'm concerned about the consistency of the base that's there. It's almost as though it hasn't cured and sanding has been a true pain. A burgundy Scotch bright pad seems to provide the smoothest surface but sandpaper has been necessary to eliminate the buried flakes. Then I'm into the challenge of the dealing with soft base balling up under the sandpaper.

At least there's almost no dust from the sanding
Thanks

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PostPosted: Wed Oct 20, 2021 7:20 pm
gprs wrote:Well, this is my first attempt at painting and, all things considered, it's been fun and is going pretty well.
Well, it _was_ going well. I laid down the base coat on the weekend and had massive issues with the paint flaking off the plastic masking film (Plazmask). It said it was rated for auto painting. Did I simply do something wrong?

I managed to more or less recover until the final coat. At that point, a one-inch flake landed square on the hood. Done. :(

I finished putting the base on Sunday evening and started sanding it down again last night in preparation for laying on a couple of coats before the clear.

Two questions:
1) I've picked up a roll of masking paper which I will use to replace the film. Is there something I could have done, or can do this time, that will reduce the risk of kicking the flakes off between coats?
2) When I started sanding last night, I'm using 400 grit, the paint kinda rolls off. Does it need more time to set? I was able to clean up the areas that I sanded but I want to ensure I'm not making more work for myself and, more importantly, not making things worse.

Thanks.



Am i hearing that you based and let it sit over night before clearing ?
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PostPosted: Thu Oct 21, 2021 5:25 am
Nope. I haven't applied any clear.
I messed up the base while spraying it (it's full of flakes that came off the masking) so I stopped before clearing.

I've let the base sit for a few days at this point and have sanded it down so that I can lay a couple more coats of base, without flakes this time I hope, before I clear.

The sanding has just been problematic. I know that there's no hardener in the base but even after 48 hours, it was so soft that sanding resulted in little balls of paint instead of dust.

I've talked to a number of local people and the reaction is the same: "well, you're not supposed to sand the base". I'm keenly aware. I'm also not supposed to cover it with flakes of crap, but here I am.

The surface is pretty good at this point after painstaking sanding and cleaning. It's certainly not hard. I can scratch it with my fingernail kinda like shoe polish.

Any advice on how I might deal with this is appreciated.
Thanks

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PostPosted: Thu Oct 21, 2021 8:56 pm
Fixing problems in base coat is always fraught with difficulty. It stays palstic and, as you found, won't sand and feather out.

Coarser sandpapers just tear it so using a fine paper like P1200 or P1500, very gently, is about all you can do, unless you remove it completely or seal it under a layer of clear and then rework over the top of that.
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PostPosted: Fri Oct 22, 2021 10:11 am
gprs wrote:Well, this is my first attempt at painting and, all things considered, it's been fun and is going pretty well.
Well, it _was_ going well. I laid down the base coat on the weekend and had massive issues with the paint flaking off the plastic masking film (Plazmask). It said it was rated for auto painting. Did I simply do something wrong?

I managed to more or less recover until the final coat. At that point, a one-inch flake landed square on the hood. Done. :(


I have never had this problem with 3M plastic masking.
I have had it happen with Paper! but only dried over spray never in Chunks.

I prefer 3M plastic masking easier to deal with than paper when masking.
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PostPosted: Mon Oct 25, 2021 11:43 am
I applied a couple more coats of base over the weekend and the result is passable. The car is cleared and ready to go again.

Thanks for all the input.

There were a number of blemishes that only because apparent once the new coats of base were applied. Some were certainly overlooked but some, I simply ran out of time to address. Each tiny nib, which would normally be quickly addressed with a quick touch of sanding, ran the risk of becoming a rash. That's the best description; in trying to eliminate the nib, just a touch too much sanding would result in the area being sanded having raised bumps just like a rash.

So, the lessons:
1) plastic is okay but be sure to mask with paper around the edge of the painted area
2) the flaking is still a bit of a mystery but is most likely due to poor technique exacerbating the lack of paper masking
3) in dealing with a small run in the newly applied base coat by wet sanding, I wonder now if the other areas would have been better addressed with a wet sanding. Perhaps this would have kept the surface temperature down and reduced the friction a bit to eliminate the "melting" of the soft base. Hopefully, I'll never have to find out.

Thanks again.



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PostPosted: Mon Oct 25, 2021 12:30 pm
IF i ever have to sand base coat i do it wet. if your getting runs on your base your applying it to wet.
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PostPosted: Mon Oct 25, 2021 12:37 pm
Yep. The base was definitely applied a bit too thick in one place and it was pretty quick and easy to rectify.

It was a small mishap during the final coat but the resolution got me to thinking...
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