Re: Removing paint from nickel plating?

[mr-asa]

Ok, here is the majority of an email from my dad. We were talking about me removing a later white top coat from the original sea green paint on a 3.3HP Johnson.
Now, Dad and I were talking about what would be gentle enough to attack the binder in the oil-based paint of the newer white paint, but not too harsh to attack the older binder in the green paint. You don’t really have to worry about that as you have a nickel finish as the original.

You can start with mineral spirits, but I’d probably head straight for the acetone. If there is any sort of original decal or original paint underneath, you might want to read through this a couple times and see what you can apply.

Good luck, and show us some before and after pics!

quote :

It’s understandable that the acetone would attack the oil-based green paint; it is a powerful degreaser, and the oil binder in the green paint qualifies as a grease. What it’s doing is denaturing the binder, removing the oil in the top layer. I have used it with success on oil paintings that had a natural resin varnish applied over the paint. But the varnish comes off very quickly, and the acetone evaporates before it can cause (much) damage to the oil paint. Yours is more difficult, especially since you don’t know what sort of paint the white is.

Remember I said that the trick is to find out what works, and then dial it back, so that you’re only removing the Bad layer without damage to the good? Try diluting the acetone, either with water or alcohol, in varying concentrations, to see if you can arrive at a controllable softening and removal of the white paint. Try a mixture of naphtha & acetone. But don’t forget that mixtures can have a synergistic effect, where the effects are more than the combination of the effect of each solvent. Same goes for following one solvent with another on the same spot of finish. As far as varying thicknesses of the later paint, well, that’s a given. The people that repaint original paint are not usually sensitive enough to try to do a good job. One strategy that might help would be to coat, with a brush, the just-cleaned green paint with an acrylic that is not soluble in the solvents that remove the white paint. For example, B-67 is soluble only in non-polar solvents, like mineral spirits (barely), or naphtha. If you painted the cleaned green with a barrier coat of B-67, then acetone/alcohol that you’re using to go after the thicker areas of white could have no effect on the green.

And you’re going to have to consider that once you get the surface cleaned down to the original paint, you will likely want to seal the cleaned green with something, because the cleaning will almost certainly have made the paint more porous, prone to chalking, and breakdown. Your choices would be a clear urethane topcoat, like is used on cars today, a coat of clear acrylic from a spray can, or B-72, which is methylmethacrylate, the monomer for Plexiglas, which gets polymerized, either by a catalyst or radiation into poly-methylmethylmethacrylate. The monomer doesn’t have a great Tg (glass transition temperature, an indicator of its hardness), so is not a suitable finish for objects that will be handled daily, like furniture, and will probably get dirty easily, but the upside is that it can be easily washed off 20 years from now and re-applied. Removing the other two clear coats would be difficult, and would certainly further damage the green paint.

I can send you dry beads of both B-67 and B-72, with instructions on their solvents.

I know this all sounds incredibly tedious, and it is. But I do it all of the time. And the only people that will appreciate your efforts to preserve original paint will be yourself, me, and a museum – if you document it. The hard part is always figuring out what works without damaging the finish you want to save. After that, the cleaning is just mind-numbingly tedious. For that, turn the stereo up, take your mind out of gear.

Remember what I said about the importance of timing and hand skills. Leaving a solvent on the surface just long enough to enable removal of the later paint without damage to the original is all about timing.