Spray Primer Cracking??
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Monte Of The Month -- June 2012
Joined: Nov 2008
Posts: 2,026
From: Iowa
Spray Primer Cracking??
So my day just got ****ty.. I spend all morning prepping my new bumper lip and now I have to start over.
I sanded the bumper with 320 gritt to get the clear coat gloss off. Then I layed down 3 coats of plastic primer. It looked good when I was done. Then I waited 1 hour like the can said, and then put a sandable primer on. Not two minutes into the first coat of sandable primer here is what it looks like. It cracked everywhere. Totally ruined. I'm going to have to sand it all off and start over.
Why did this happen??
I sanded the bumper with 320 gritt to get the clear coat gloss off. Then I layed down 3 coats of plastic primer. It looked good when I was done. Then I waited 1 hour like the can said, and then put a sandable primer on. Not two minutes into the first coat of sandable primer here is what it looks like. It cracked everywhere. Totally ruined. I'm going to have to sand it all off and start over.
Why did this happen??
what brand of plastic primer did you use?
** edit** what kind of paint and everything are you using?
** edit** what kind of paint and everything are you using?
Last edited by Budsjlm; Apr 6, 2012 at 02:49 PM.
Thread Starter
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Monte Of The Month -- June 2012
Joined: Nov 2008
Posts: 2,026
From: Iowa
Once I saw the Rustoleum primer cracking I stopped, so I only did half of the bumper. As a test since I can't mess it up any worse, I sprayed some black top coat that I'm going to use (duplicolor) on the other half and it looks awesome. The duplicolor on top of the plastic primer turned out great. I shouldn't have used this rustoleum filler primer and just gone straight to color. I was just trying to fill in the scratches though.
Thanks.. sucks when these things happen.
Last edited by zzapultimate; Apr 6, 2012 at 03:06 PM.
From what I looked up it is cause becuase your plastic primer dries slow and is still kind of soft
Which it is basicially a flex agent in it to keep it from cracking if pressure is applied
And the sandable dries quicker and hard hens causeing the cracking,
If you have somthing you can experiment with and can spare the paint try doing the plastic primer let it set up then shoot both at the same time kind of mixing them, it may work as a flex agent and you may be able to use the sandiable primer
It's wired the plastic primer wants it to set up for an hr mine says 10 min
Which it is basicially a flex agent in it to keep it from cracking if pressure is applied
And the sandable dries quicker and hard hens causeing the cracking,
If you have somthing you can experiment with and can spare the paint try doing the plastic primer let it set up then shoot both at the same time kind of mixing them, it may work as a flex agent and you may be able to use the sandiable primer
It's wired the plastic primer wants it to set up for an hr mine says 10 min
Last edited by Budsjlm; Apr 6, 2012 at 03:15 PM.
Monte Of The Month -- October 2012
Joined: Dec 2010
Posts: 2,886
From: Ames, IA
I had similar problems with rustoleum and plastic.. tried to prime an old sub box that had a plastic front and I sanded really good and prepped correctly but the rustoleum primer just didn't work well. Ended up using duplicolor, I think? and it turned out great. I've never had good results from rustoleum except on a rusted out lawn mower lol.
I used Valspar plastic primer, followed by gray rustoleum sandable primer.
Once I saw the Rustoleum primer cracking I stopped, so I only did half of the bumper. As a test since I can't mess it up any worse, I sprayed some black top coat that I'm going to use (duplicolor) on the other half and it looks awesome. The duplicolor on top of the plastic primer turned out great. I shouldn't have used this rustoleum filler primer and just gone straight to color. I was just trying to fill in the scratches though.
Thanks.. sucks when these things happen.
Once I saw the Rustoleum primer cracking I stopped, so I only did half of the bumper. As a test since I can't mess it up any worse, I sprayed some black top coat that I'm going to use (duplicolor) on the other half and it looks awesome. The duplicolor on top of the plastic primer turned out great. I shouldn't have used this rustoleum filler primer and just gone straight to color. I was just trying to fill in the scratches though.
Thanks.. sucks when these things happen.
, I mean it was in the plans anyway but didn't plan to do it this soon 
I had similar problems with rustoleum and plastic.. tried to prime an old sub box that had a plastic front and I sanded really good and prepped correctly but the rustoleum primer just didn't work well. Ended up using duplicolor, I think? and it turned out great. I've never had good results from rustoleum except on a rusted out lawn mower lol.
Thread Starter
|
Monte Of The Month -- June 2012
Joined: Nov 2008
Posts: 2,026
From: Iowa
From what I looked up it is cause becuase your plastic primer dries slow and is still kind of soft
Which it is basicially a flex agent in it to keep it from cracking if pressure is applied
And the sandable dries quicker and hard hens causeing the cracking,
If you have somthing you can experiment with and can spare the paint try doing the plastic primer let it set up then shoot both at the same time kind of mixing them, it may work as a flex agent and you may be able to use the sandiable primer
It's wired the plastic primer wants it to set up for an hr mine says 10 min
Which it is basicially a flex agent in it to keep it from cracking if pressure is applied
And the sandable dries quicker and hard hens causeing the cracking,
If you have somthing you can experiment with and can spare the paint try doing the plastic primer let it set up then shoot both at the same time kind of mixing them, it may work as a flex agent and you may be able to use the sandiable primer
It's wired the plastic primer wants it to set up for an hr mine says 10 min
I had similar problems with rustoleum and plastic.. tried to prime an old sub box that had a plastic front and I sanded really good and prepped correctly but the rustoleum primer just didn't work well. Ended up using duplicolor, I think? and it turned out great. I've never had good results from rustoleum except on a rusted out lawn mower lol.
