epoxy primer mapping and temperature

ross52

Promoted Users
Regarding the epoxy primer mapping issue. I've been thinking about this quite a bit and I'm quite surprised by this phenomenon, given the rave reviews of SPI epoxy primer. With most restorations there is going to some bondo used and in many of the restorations there is going to be a lot of bondo used. So, in all of the areas where bondo has been used, you will most likely have to scuff and reshoot these areas again. I don't know about you, but I think that's a lot of extra work, especially if you're doing this in your garage, where you have to worry about fumes, dust, temperature etc. With that being said, I have to believe there is away to prevent masking, such as: letting the bondo set longer before priming, spotting the bondo with a sealer or another coating such as lacquer, that will block the effects of the bondo causing the mapping. Just my thoughts.

On another subject, after spraying epoxy and keeping the temperature at 70 degrees for the first 24 hours, are there any temperature requirements/recommendations beyond that? Thank you
 

elwood

Promoted Users
Something to consider.
Filler also absorbs water. That is something you can't see but is there. Filler is absorbing the solvents from the primer. Something you can see the effect of. When it absorbs water the effect is not seen. It will absorb solvents from any thing that has it as part of the formula that it's made of. It's just not as noticeable when 2k primer is used. But it's still there.
Usually the mapping disappears after the second or third layer of epoxy. I use epoxy for my only primer and I've never had anything show thru or come back later.
 

sprint_9

Rookie
The mapping issue I discussed earlier was referring to epoxy as a finish coat. If you do desire epoxy as a finish coat an extra step of bodywork is probably going to be required if your applying over filler. Otherwise its something that happens and is really of no concern in most cases.
 

John Long

Member
Ross, it really is a non issue. You are not going to paint on top of two coats of epoxy that was applied on top of body filler. If you have applied body filler and blocked it, you will have to put primer over that and block again. No one is going to block filler and feather it well enough to be ready for final paint.

With that said, you can apply epoxy and use it for final blocking or shoot 2K primer surfacer or a high build polyester primer as needed. ignore the mapping if you are going to do your final prep. The only time it will be a concern is if you want to leave the car in epoxy and don't intend to cover it up. In that case the extra sanding and re-application will be necessary. Remember though. Only SPI, as far as I know, has UV protection built in and can be left uncovered.

John
 

texasking

Promoted Users
There is not a quality restorer in the world that would expect to be able to spray 2 coats of anything over filler and it be ready to paint. There is not a better product than SPI epoxy to spray over filler as a first step. Spraying lacquer would be the worst thing you could do. It does not block solvent or moisture and shrinks for months if not years. The epoxy is "blocking the effects" of mapping by completely sealing off the filler from moisture or solvent in subsequent coats. If you sprayed 3-4 coats initially, the effects of the mapping would be much less or nonexistent, but doing it in 2 steps eliminates it, by letting the solvent escape, and letting it cure enough to completely seal off the porous nature of polyester. Anything you spray over a porous surface will look different than a surrounding non porous surface when dry, and will need to be sanded to correct it.
 

jcmeyer5

Promoted Users
I’d expect to have to sand the two coats before sealer, assuming irregular surface underneath. I’ve found that after sanding with 180 to the paint where all gloss is gone, but not breaking through, that mapping goes away with the next coat.
 
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