White marks in grain under lacquer finish.

[quintodam]

I’m actually an accordion maker. I hope that doesn’t put any potential answerers off. I recently finished a few boxes with raw linseed oil and let it dry for a few days. I then sprayed on 1 coat of cellulose sanding sealer mixed 50/50 with thinners. Then I finished with 3 coats of 2 part precatalyzed lacquer with some retarder added in nice warm weather. After 3rd coat the deep grain showed up white. Have no idea what part of preocess may have caused it. Any help appreciated. 

[Bizman62]

Hi and welcome! Crossing borders should be a norm rather than an exception. Even more so when it comes to woodworking, although painting cars is not too different to painting guitars...

I'm by no means a master in finishing although I've managed to get decent results. There's a couple of things I've learned, though.

First, "warm" doesn't mean the same as "dry". Here in Finland the driest time of the year is usually around February when it's also coldest. All the moisture has been frozen. You may think that a desert is dry like the Sahara but during the night when it's cold the moisture in the air concentrates to droplets on surfaces like leaves and that's why most living creatures there come out at night only. Warm air can hold much more water than cold.

Second, although linseed oil hardens in the wood cells the process takes more than just a few days. Raw linseed oil dries even slower than boiled. A few weeks before changing to another type of finish might be worth the waiting even with boiled, with raw I'd wait for months! The curing process of the linseed oil will release vapours that can make a clearcoat milky.

Third, shellac is known to work with most anything so applying a layer of it between two different types of finishes is recommendable to avoid problems.