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ok so i started painting tnriverrat's vector and had it all sanded down then i when i started primering it the primer started to crack very bad all over it looked like a dryed up muddle puddle in 120degree weather i sanded them out 3 times still could see them alittle bit then one finale sanding and they was gone so i painted it and still got some that came thru what causes this didnt see them in the paint below just in the primer mixed it like i have a hundred times before and never no problems till now

What kind of primer? Did it begin to crack immediately or as it dried? Did you wipe down with a prep solvent of some sort? I've seen primer mudcrack if it is laid on too heavy as well. It really sounds like surface contamination to me, probably wax. I had a guy bring an old stratos bass boat to me a few years ago to be painted. I was looking the boat over and noticed to gel just didn't feel right. I asked him what he had been putting on the boat and he said brake fluid Long story short, nothing we tried would remove the surface contamination from that boat.

brianincc wrote:What kind of primer? Did it begin to crack immediately or as it dried? Did you wipe down with a prep solvent of some sort? I've seen primer mudcrack if it is laid on too heavy as well. It really sounds like surface contamination to me, probably wax. I had a guy bring an old stratos bass boat to me a few years ago to be painted. I was looking the boat over and noticed to gel just didn't feel right. I asked him what he had been putting on the boat and he said brake fluid Long story short, nothing we tried would remove the surface contamination from that boat.

i used some 3m grease wax remover that i believe was bad. it wouldnt ever dry and should of dried like solvent. it caused same reaction when i tried to apply sealer over it.

i used laquar thinner for cleaner sanded the old paint down to paint thru the clearcoat prepped it much as possible the primer was dupont primer same stuff ive all ways used and mixed the same as always just kept cracking and used nason paint for top coat waiting to go see it in the mourning wasnt really cracking when i left should be okie

The best thing I have found for a prep solvent short of using what the paint manufacturer recommends is clear rubbing alcohol. It evaporates fast and contains no impurities to cause problems. Most thinners like acetone and lacquer thinner can cause problems under solvent based finishes. Most thinners purchased at the box stores are wash grade,which means just that ,they are good for cleaning your tools at the end of the day. Another thing I see people do that will cause problems is simply pouring solvent on a rag and going around the project from one end to the other. All you have done is move the contaminates farther down the line. Use a two rag system, pour solvent on one and follow immediately with a clean dry rag and change rags often. I usually will do this twice at least before I begin to spray any kind of primer,sealer. I hope this helps .