Troubleshooting Unwanted Crackle

      Crackle shows up in a catalyzed primer over vinyl sealer on stripped furniture. Why? October 17, 2012

Question
My buddy brought in some chairs that he had stripped without using chemicals. They had layers of paint on them. I asked him about Pledge use and he said there had been none. I used a vinyl sealer (MLC Water White Vinyl Sealer) and scuff sanded. Next, I used black Clawlock primer (MLC). As the primer was drying, it started to crackle. I sprayed a few more coats and it mostly covered the crackle but some eventually returned.

I have heard that you can put catalyst in the vinyl when putting a catalyzed finish over it. I didn't do that. Is that what caused the crackle to happen? Or is there something else going on here?

Forum Responses
(Finishing Forum)
From contributor A:
Since you applied a post cat primer, you should have catalyzed the vinyl sealer. It sounds like there is a surface tension problem going on.



From contributor B:
Primer is made to go over raw wood. Primer over anything else makes a real good crackle finish. I would either go with the vinyl or a 2k isolante coating over the original cleaned and sanded existing finish and then build with a sealer if needed or go directly to your pigmented finish or clear coat.


From the original questioner:
The chairs are done and the guy is happy. Why not? It was free.
I just wanted to know what was causing the crackle. I have put the primer over lots of things except vinyl sealer. That includes lots of clears and even cured pre cats without a problem.

I was pushing things. I really didn't let the vinyl dry for long, maybe 20 minutes at 72F with airflow. I sanded it and primed. The vinyl was a bit rubbery while sanding, but it always is, even when dried for hours.



From contributor A
Glad things turned out ok, but as a rule, you should not put a post cat over a pre cat. That's why the vinyl sealer has the option of being post catalyzed .You can't put a hard finish on top of a soft finish, but you can put a soft on top of a hard finish without surface tension problems.


From the original questioner
I know that, and it isn't something that I do normally. But when I am spraying clears and pigments on the same cabinet I have areas that I don't care about, like the bottom of the cabinet on a lower, I don't have any problem with wrinkling.


From contributor B
"But when I am spraying clears and pigments on the same cabinet I have areas that I don't care about, like the bottom of the cabinet on a lower." In those situations I use a pigmented sealer. Works great and dries fast. Just tint with a compatible UTC colorant.



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