Ask the Expert: Overcoating Polyurethane with Nitrocellulose Lacquer

Q: I am going to spray paint a car which was sprayed with two pack paint. I now want to spray paint it with cellulose. Will I have any problems with spraying the cellulose paint over the two pack. Will it react in any way ie: Blister, not dry properly or any other problem you can think of. Let me know all you can.

A: In all probability you will not experience softening or blistering because the two-pack material (probably a polyurethane) is sufficiently solvent resistant that it won't be affected by the lacquer thinners. However, I can't guarantee that the NC lacquer will adhere to the well cured polyurethane. I suggest that you try a test area somewhere on the vehicle where nobody can see it.

Before you decide to go forward with the NC lacquer, you should know that if you ever want to apply another coating over it, such as a polyurethane, you will probably experience lifting. Any paint that contains lacquer thinners or strong solvents similar to it, will soften the NC lacquer.

Best wishes,