2k Primer Shrinkage

J

jcpettit

Promoted Users
Hey Guys I am looking for a little input. I do collision repair and have been using SPI 2k primer for the past year or so. I used to have problems with terrible primer shrinkage in the past but have not had the issue show up since I switched to SPI. Until last week. I fixed a dent on a car and used Rage filler over the dent. I finished out the Rage with 80 grit and then used Dolphin Glaze to finish up. I used 180 grit on the Dolphin Glaze and I usually try to take the glaze over the feathered paint edge to help reduce shrinking and mapping out later. I then applied 2 coats of 2k primer and I always try to wait around 10 minutes between the coats. The next day I blocked it with 320 grit and then applied 2 more coats of 2k with 10 minutes flash time. Then the next day I sanded down with 400 grit and painted. It just so happened that the customer did not pick up the car until after 2 weeks and when I backed the car outside the day they were supposed to pick it up I noticed the shrinkage. I was able to sand and buff the clear to take care of it, but I am wondering what I did wrong. Hight temps here were around 70 to 75 degrees during my repair.

Also, I use a 1.7 tip for my primer.
 
How do you know the shrinkage was in the primer?
Wouldn't primer shrinkage show scratches that wouldn't buff out?
If you could buff it out, it sounds like it was the clear.
 
.....or.....if the shrinkage looks like your block sanding marks then the shrinkage is in the filler stages. since primer is only filling in 180 grit then those are scratches too fine to show up later. the 80 grit is what will usually show. i have had scratches come back many times when i used dolphin glaze over 80 grit. you have 2 different fillers working together there. i would be taking you filler to 180 then do a skin coat of dolphin and block that with 180-220. this way your not relying on the next step in your process to take care of something. remember, if its not there it cant come back to haunt you.
 
We've been finishing out our bodywork in 220 or finer to help avoid this problem. A second application of primer should not be necessary in most cases, imo, unless you are going for a really custom look. A better procedure would be to go with three coats, then open up the surface the next day by blocking with 320, then heat lamp it until any solvent smell dissipates. Then finish with 600 and paint.

If you have to apply primer twice, just do the same procedure twice, use a heat lamp after blocking off the top layer of primer to drive away remaining tail solvents.
 
I use evercoat metal glaze sand 220,,and then i go over with spi 2k sealer as a primer let it dry in sun and apply more if i need to sand again 400 final or 600 ect.. and i always get some shrinking but can be remove with 1500 wet i see it more in black of course.
 
crashtech said:
We've been finishing out our bodywork in 220 or finer to help avoid this problem. A second application of primer should not be necessary in most cases, imo, unless you are going for a really custom look. A better procedure would be to go with three coats, then open up the surface the next day by blocking with 320, then heat lamp it until any solvent smell dissipates. Then finish with 600 and paint.

If you have to apply primer twice, just do the same procedure twice, use a heat lamp after blocking off the top layer of primer to drive away remaining tail solvents.
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This is what i was about to ask if sanding primer with 320 and let it breathe while is drying can help..what i get is more of a soaking little shinking since some 1500,2000 ect will fix this issue for me plus i dont buff right away i waiit the most i can.
 
Yes, I did not mention but it was on a black vehicle so it might not would have been as noticable on another color. The more i think on it the more I think Jim might be correct. I think the shrinkage might be in the dolphin glaze. On one small spot I used a DA with 80 grit to sand the Rage filler and I am almost positive that I remember seeing DA sand scratches in the shrinkage. I never touched the Dolphin glaze with a DA as I only used 180 on a block. It sounds like I should be finishing out the Rage with 180 and then maybe 220 on the Dolphin Glaze.

I have always done my priming in 2 applications because that is the way I was taught. However, lots of corners were cut by the person that taught me and many times primer was used to fix imperfections in the actual filler. I prefer to have my filler nearly perfect before priming, so many times I have wondered if 3 coats and a single application would be ok but have always done 2 applications to be safe. But can I assume that since I have been adding a 2nd application that I am just piling more solvents on and increasing the chance of shrinkage later?
 
jcpettit said:
...I prefer to have my filler nearly perfect before priming, so many times I have wondered if 3 coats and a single application would be ok but have always done 2 applications to be safe. But can I assume that since I have been adding a 2nd application that I am just piling more solvents on and increasing the chance of shrinkage later?
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Multiple primer applications are used in custom and restoration work, there it is expected and necessary. But on everyday jobs this is not a plus, because there just isn't enough time for so many layers of primer to fully cure out. Give the three coat method a try, I think that if your bodywork is good, you might be surprised at how smooth you can get it with just one primer application. On small damage, we use just two coats, and that's normally plenty, unless a body line or edge gets sanded through, which is an easy fix.
 
It could be shrinkage in all three, filler, glaze and primer. Just saying....Every product we use shrinks, some worst than others also some different than others. I've noticed Turbo 2k shrinks most early (within a couple of hours), regular 2k shrinks over night. Most body fillers shrink in a couple of hours. Any of them over applied exaggerates the problem and should "sit" longer to let them finish shrinking.
 
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