Paint allergy

[Gary Mitchell]

A couple of times in history I've tried to paint over an older coat of anonymous origin just to have it curl up at the introduction of the new stuff. Any comments or suggestions are welcome as I am currently about to mix brands again. thanx in advance,,,, gm

 

[JD Dave]

When you do that, you never quite know what's going to happen with the former undercoat. You could do a trial shoot in a small area or you could prime it with an epoxy or Evercoat which seals off a good quality base. Whichever you choose, preparation is crucial. That means, hot powerwash, Prep-Sol clean, dry, wire brush, carefully!! sandblast and hand sand, then Prep-Sol clean again. Absolutely no dirt, oil or silicone residue.

 

[showcrop]

This happened to me with a couple of my early tractors, when trying to spruce them up a little with aerosol paint. I figured out that it is one of the reasons for using primer, but not aerosol. I have since painted over plenty of earlier paint after abundant use of a cup type twisted wire wheel, followed by a good primer, usually epoxy.

 

[glennster]

putting lacquer paint or primer over enamel will cause that. you need to apply a sealer over the old paint

 

[Stephen Newell]

A couple of times in history I've tried to paint over an older coat of anonymous origin just to have it curl up at the introduction of the new stuff. Any comments or suggestions are welcome as I am currently about to mix brands again. thanx in advance,,,, gm

A lot depends on how fresh the original paint is. If an enamel has dried for decades it's a lot more forgiving. When you prep the old paint if you scuff sand with coarser paper it may lift where if you scuff sanded it with 400 grit it wouldn't. Deep scratches will enamel the solvents to penetrate better. Still it's better to test a small spot before you start spraying the whole tractor. It comes down to the solvents in the new paint, especially rattle can. Most rattle can paint contains acetone which is very strong to apply to enamel. How you spray it can also affects whether it works or not. Several light coats will usually go better than a thick juicy coat.