Good afternoon, Busy with a Coleman 201. Tank was fairly badly peeled and rusted. Sanded prepped and sprayed with a self etching primer from a spray can. Let it dry all good so far. Decided to use Rustoleum Hunters Green for the top coat. Sprayed 2 light coats with drying time in-between. I was not happy with the finish as it had slight lemon peel. Left it for a week and this afternoon gave it a sand with #1200 grit waterpaper. Got it nice and smooth. The finish was decidedly matt with the typical sanded look. Washed it down carefully and being slightly impatient hit it with a hair drier to speed things up a bit. Blow me down the more I dried it and the warmer the tank got the more it started to shine!!!!. Bloody sorry I rubbed through to the primer in places.. Any idea why this might have happened??
Some paints do shine up more after some heat-curing. There are many possible reasons. I can't give you the exact process that had actually taken place. I don't know the paint base of that particular Rustoleum Hunter Green but it might be a solvent-based acrylic enamel. You have sanded it down as smooth as the 1200 grit would allow. This significantly evens out the thickness of the paint over the fount. The paint hasn't fully cure yet at that time. As you heat it up, solvents would continue to evaporate. While doing so, the binding resins were still able to 'reflow' to some extents, with an effect that is visually similar to vitrifying the resin particles. The initial matt finish after sanding was due to exposed pigments and other solid fillers. The reflow would allow the lighter binder resins to rise up to the top and coalesce while the heavier pigments and fillers would settle down to lower levels of the film. The binder resin would then take the form of a smooth, continuous film with greatly reduced 'micropeaks and valleys' over the surface. As the solvents were gradually lost, the paint film would shrink and form a tighter, somewhat stretched film over the fount's surface. Once all the solvents are lost, the paint would also undergo an accelerated chemical cross-linking that makes it more solvent-resistant. All this would make it glossier at the end. It also makes the film harder.
Hi MYN, Thank you for the explanation. Could one reliably repeat this process as it would make a mighty fine looking finished product.
Yes you can, but not for all types of paints. Sometimes, heat curing undesired effects and thus not recommended by the manufacturers.
