Paint Primer cracking!

[liltank]

This is the first time I've experienced this. I've painted this stock in the past with success. But when I sanded and hit with primer, the primer is cracking when it dries. Do I have contamination on the areas that it is cracking? It is a B&C Medalist A2. After the last sanding before I tried the first coat of primer, I blew it off with the air nozzle. Then I wiped it down with Witch hazel (didn't have denatured alcohol) to get the dust the nozzle didn't get. Did the witch hazel contaminate the stock?

 

[Dr. Vette]

I use PPG wax and grease remover (automotive) but you can buy similar products at most auto parts stores.

I suspect your prep agent didn't help at all. Lacquer thinner or enamel reducer would work in a pinch, but the wax and grease remover works every time for me.

 

[liltank]

Thank you.

 

[moombaskier]

The witch hazel must of had some type of oil in it. The cracking is definately caused by contaminates on the stock. I'm not sure witch hazel can even cut the oil from your fingers. The air you used could have had contaminates in it as well. It's happened to me before and your gonna have to clean everything off and start over.

 

[buzzgun]

I spent about 10 years in the chemical coating industry, mostly dealing with automotive and chemical coatings....

The defect in the photo above is not from contamination.......contamination does not cause the type of "cracking" your photos show. What I am seeing in your photos is called "lifting" and is caused by the solvents in the fresh primer penetrating the previous coat of paint and causing it to swell.....or, the undercoat is absorbing the solvents and they are trying to come out after the primer is dry on the top.

Basically, your primer is incompatible with the previous paint........you either need to strip the stock, or sand it smooth and find a water based primer/sealer to seal the undercoat from the new topcoat and prevent the solvent of the new topcoat from penetrating into the substrate.

If it was mine and I wanted it done right, I'd strip the stock and start over.

 

[Dr. Vette]

I spent about 10 years in the chemical coating industry, mostly dealing with automotive and chemical coatings....

The defect in the photo above is not from contamination.......contamination does not cause the type of "cracking" your photos show. What I am seeing in your photos is called "lifting" and is caused by the solvents in the fresh primer penetrating the previous coat of paint and causing it to swell.....or, the undercoat is absorbing the solvents and they are trying to come out after the primer is dry on the top.

Basically, your primer is incompatible with the previous paint........you either need to strip the stock, or sand it smooth and find a water based primer/sealer to seal the undercoat from the new topcoat and prevent the solvent of the new topcoat from penetrating into the substrate.

If it was mine and I wanted it done right, I'd strip the stock and start over.

Do you think that if he stripped it and sanded it, and had a buddy who does automotive body work spray it with epoxy primer that it would prevent this with the next coat?

I know that DP 90 is popular as a primer and sealant, for example.

 

[bigngreen]

Snap hoss, I see sanding in your future!!!!

 

[liltank]

Snap hoss, I see sanding in your future!!!!

LOL! I see a stripper in my future!..... wait.... that came out wrong. I need to buy a stripping solvent and take the paint off that way.

 

[SidecarFlip]

Stripping solvent???

No, elbow grease and abrasive paper......

 

[liltank]

No, elbow grease and abrasive paper......

Elbows are getting lubed as we speak. I'm impatient and can't wait to get to the hardware store. Belt grinder did quick work. Now I'm in the process of body putty filling holes.

 

[Dr. Vette]

Don't forget - body putty may shrink a bit, depending what quality you bought.
Just a tip.

I know that on old Corvette bodies the DP 90 epoxy primer seals them very well and protects the new expensive paint jobs from having issues. If you know a body man I'd bet he would spray your stock at the same time he's spraying another car.

 

[liltank]

Thanks guys for the help. I found out that the Krylon ultra flat camo paint will go right over the blue metallic w/o any issues. So I left the primer on the spots that didn't have problems, and used the Krylon for the spots that did. She aint pertty, but she'll be effective.

 

[SidecarFlip]

Doctor Vette... I love it.........

I just had a flashback to my 66 Stingray Convertible, 427/390, Milano Red, tan leather interior, cast aluminum wheels with knock off's and off roads. All the girls loved it and I loved all the girls......

I wrapped her around a utility pole many years ago. Oh well. Snot bodies don't mend well. My next ride will be a Cadillac CTS with the 550 and a 6 speed. Lugs your *** in style and goes like a scalded dog......

Far as body filler goes, I'd be using 3m glazing compound for minor imperfections.

I sort of liked the 'textured' look in the first picture. Better grip........

 

[buzzgun]

Do you think that if he stripped it and sanded it, and had a buddy who does automotive body work spray it with epoxy primer that it would prevent this with the next coat?

I know that DP 90 is popular as a primer and sealant, for example.

Depends on the type of solvent in the primer he uses and what material is left on the stock. If he strips it back to the gelcoat, then he could use most types of primers.

If he has a buddy who does auto body work, that buddy probably has access to a water based primer/sealer.......water won't penetrate the existing material and cause it to swell like many other types of solvent will.......that is why I suggested a water based primer/sealer.