Polyester primer?

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PostPosted: Tue Dec 14, 2021 6:09 am
I’ve read that polyester primer should be sealed almost immediately after application and sanding because the primer sucks up moisture. Is this true? I understand it depends of the humidity in my garage. Are we talking about hours? Within the same day? Or is it safe to leave it a few days?

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PostPosted: Tue Dec 14, 2021 9:11 am
I just treat them no differently than I would exposed bondo/filler on the car. That's basically what most of these are....sprayable bondo. I would indeed get it in primer as soon as is reasonable. I know a few custom paint guys that get it on, and roll the car out in the sun on and off for a few days to make sure that it is done shrinking/moving. Personally, I like for it to set at least a week before moving on and yes, I do that sun thing for a few days myself....
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PostPosted: Tue Dec 14, 2021 1:35 pm
As stated it is basically spray on body filler.
It sets up chemically and is not supposed to shrink like other primers.
Unless you are exposing it to rain or washing it with water, you should be fine letting it set.

You will need to be sanding much of it off anyway as you block sanding the panels.
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PostPosted: Tue Dec 14, 2021 1:46 pm
^^^^^You know that is a good point there.... you should indeed be getting it mostly sanded off. Every time I've seen poly primers fail on cars most of the guys told me they were like at an 1/8 to 1/16 inch of a "shell" of the stuff left on the car.....
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PostPosted: Tue Dec 14, 2021 2:36 pm
Another question regarding aplication.. Could I "spot" prime low spots that I know about, say a couple of coats, and then a coat or two on the entire panel?
If you look at the picture of the roof of my car on first page, the low spots are mainly consentrated where the support bars lies below.

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PostPosted: Tue Dec 14, 2021 5:09 pm
Yes.
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