Mapping problems with 2K Regular Build Primer

DrivenImageAuto

DrivenImageAuto

New Member
Hello, so here is the run down of the problem I'm having:

Started using SPI 2k primer a short time ago, looking for a more cost effective alternative to the PPG primers I was using

Car that was worked on had a previous paint job, however the (replacement) hood on it was OEM paint, car was blocked completely and finished in 320 before primer

In some areas where high spots, the blocking naturally cut through the clear and base coat on both the body and the hood, you could see the previous layers, did some minor fills with USC icing ect

On to priming: 4:1:10% Mix sprayed through a 1.6 with 5min flash in between , temps were over 80 degrees at the time Florida, total of 3 medium coats

Parts sat out in the Florida sun for a little over a month, back inside, blocked flat, finished in 320 added another two light coats of SPI 2k Primer about another 3 weeks of dry time in the sun (project car of mine had no rush)

final block sanding 320 then 400 then 600 parts were smoooth AF

Sprayed 3 coats of PPG base reduced 1:1 about 15mins in between coats, used my sun gun at an angle and started to notice repair mapping / sand scratch swelling :oops:

I decided to 800 grit the base coat in SOME of the swelled areas but not all, clear coated two hrs later

The you could immediately start to see the mapping start to show, and proceeded to get worse over the span of two weeks as the clear coat cured in the sun, Euro2020 sprayed 4:1:2

The areas where I had leveled out the mapping on the basecoat with 800 did not swell through as much after clear coat

The only thing I can think of is that the solvents are being absorbed by the 2k primer and the layers below it are reacting to the solvents causing the mapping, other than that I cant think of anything else, the only other time I ever had this problem whas when a Medallion rep came by and we tried their primers and it has terrible, it swelled up the repairs right away and the mapping was horrible.

Any imput would be greatly appreciated thanks in advance !

(FWIW: I also got heavy mapping on the hood and that had OEM finish)
 
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If your mix ratio was 4:4:10% as you wrote, then that is a massive over activation. 2K reg. build is 4:1 not 1:1 (4:4). Hopefully that was a typo. I use the same basic products and procedure that you noted with no issues. Sometimes I epoxy seal, sometimes I don't. Most of my projects are low rent beaters.
 
RenewAP said:
If your mix ratio was 4:4:10% as you wrote, then that is a massive over activation. 2K reg. build is 4:1 not 1:1 (4:4). Hopefully that was a typo. I use the same basic products and procedure that you noted with no issues. Sometimes I epoxy seal, sometimes I don't. Most of my projects are low rent beaters.
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Subscribing......

Good catch, I noticed that too and wondered if it was a typo. Waiting for the OPs's feed back on that question.
 
i have used all the spi primers over the past 20 years and yes, as with any 2k urethane there is some slight shrink or swell but its no worse than any 2k i have used from any other big manufacturer. only thing i can think of is if once you sanded the primer and went through all the grits that the primer was really thin in areas offering very little to no solvent barrier and your base or repair edges soaked up the solvent and swelled up.
 
Jim C said:
i have used all the spi primers over the past 20 years and yes, as with any 2k urethane there is some slight shrink or swell but its no worse than any 2k i have used from any other big manufacturer. only thing i can think of is if once you sanded the primer and went through all the grits that the primer was really thin in areas offering very little to no solvent barrier and your base or repair edges soaked up the solvent and swelled up.
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Thanks for the reply, hmm it its possible that It might have been thin in certain areas, although I didnt cut through on the second round this does make some sense
 
RenewAP said:
If your mix ratio was 4:4:10% as you wrote, then that is a massive over activation. 2K reg. build is 4:1 not 1:1 (4:4). Hopefully that was a typo. I use the same basic products and procedure that you noted with no issues. Sometimes I epoxy seal, sometimes I don't. Most of my projects are low rent beaters.
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In the same boat, sometimes I epoxy sometimes I don't, this one project I didn't.
 
Well if it's going to be thin, it will be thin over defects because that is where you are blocking things flat. I agree it may be a long shot but its the only thing i can think of at the moment.
 
Were you spraying the base really wet? No sealer and wet base can cause that. That would be my guess. You are spraying it wet and the solvent is attacking the already susceptible undercoats. Without being there seeing the car and your procedures in person we are all just guessing though. Basecoat is designed to be sprayed in medium coats at most. Never spray it wet. Can lead to a host of problems.

When you get a lot of sand throughs and are using urethane primer it can be a crapshoot. Some OEM paint reacts like refinish and will map, others don't. Personally I don't ever like to sand through OEM clear then urethane over it. Do your blocking with the 2K. You aren't blocking anyways sanding OEM paint cause there is not much there. And like Jim said you got to make sure that there is plenty of material on there if you are using 2K urethane. Or in the future spray a couple of coats of epoxy and lock the area down before moving on to 2K urethane. And seal it. Sealing it always helps in a situation like this, even if it's a urethane sealer.
 
Jim C said:
i have used all the spi primers over the past 20 years and yes, as with any 2k urethane there is some slight shrink or swell but its no worse than any 2k i have used from any other big manufacturer. only thing i can think of is if once you sanded the primer and went through all the grits that the primer was really thin in areas offering very little to no solvent barrier and your base or repair edges soaked up the solvent and swelled up.
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Valuable information right there.
 
if you spray alot of candies you will figure this one out quick. candy dyes migrate with solvents and if you dont have a certain mil thickness of primer over a filler spot after blocking then the filler will suck the dye right out of the base binder leaving a light blotch the shape of the filler. this is why its never optional to do a candy job without spraying a sealer first. of course what chris touched on was good as well and goes hand in hand with this. the wetter you spray the more time those solvents have to soak in through the primer.
 
Chris_Hamilton said:
Were you spraying the base really wet? No sealer and wet base can cause that. That would be my guess. You are spraying it wet and the solvent is attacking the already susceptible undercoats. Without being there seeing the car and your procedures in person we are all just guessing though. Basecoat is designed to be sprayed in medium coats at most. Never spray it wet. Can lead to a host of problems.

When you get a lot of sand throughs and are using urethane primer it can be a crapshoot. Some OEM paint reacts like refinish and will map, others don't. Personally I don't ever like to sand through OEM clear then urethane over it. Do your blocking with the 2K. You aren't blocking anyways sanding OEM paint cause there is not much there. And like Jim said you got to make sure that there is plenty of material on there if you are using 2K urethane. Or in the future spray a couple of coats of epoxy and lock the area down before moving on to 2K urethane. And seal it. Sealing it always helps in a situation like this, even if it's a urethane sealer.
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Yea you're right. I'm going to have to try that next time

First coat of base fairly dry second and third medium, the reducer although slow was evaporating fairly quickly I would say it would turn Matt in a out 2-3 mins or so

I'll upload some pictures later

When I block the oem coat is to get it glass like flat on some very very minor waves and that's why I blocked

Thanks for the input!
 
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