What can cause primer checking?

[Kez]

All,

I am making a plug for a open cockpit tunnel cowl. I carved it out of solid pine and then filled with Bondo. Normally I would spray with a rattle can auto primer; sand and repeat several times. This time I spray on a clear lacquer first thinking that it would help fill the grains faster.

Problem I have is that the primer cracked (I think the proper term is checking) as it dries. I am wondering if the clear lacquer underneath is the cause. Yes, I let the lacquer dry for several days before spraying on the primer.

Please share your experience.

Thanks,

kez

 

[Hydro Junkie]

I know lacquer is not compatible with many paints if applied over the top, seen that personally. Did you scuff sand the lacquer before you applied the primer? It is possible that the primer shrank as it dried, causing the primer to crack due to it having nothing to grip

 

[JamesShields]

Did you sand the lacquer? Is the primer comparable with lacquer? Are my first thought. I always seal with epoxy first then sand and paint.

 

[JamesShields]

I also like to fill with epoxy and microbaloon. Not bondo

 

[Dan Kramer]

probably too heavy, tried to use it like filler?? just guessing. best to use 2k activated primers for this stuff . tried and true methods that work. just saying.

 

[happybradboating]

I also like to fill with epoxy and microbaloon. Not bondo

The microbaloon is great stuff! It can be used to fill in about anything and with the right mixture will sand down good. I like using it to repair bump and rub damage. At this point I have a boat to repair after the last race and have it ready to apply the microbaloon and epoxy mixture.