Conversion Varnish over Linseed Oil

Tips for success with a conversion varnish topcoat applied over boiled linseed oil. June 18, 2013

I have some cherry furniture to spray that has had a light coat of linseed oil rubbed on. The linseed oil has been drying for six days. Can I safely spray Kemvar cv on the linseed oil. The Kemvar is self-sealing so I have just been thinning it for my seal coat and not using vinyl sealer. Also, should I light sand the linseed oil?

Forum Responses
(Finishing Forum)
From contributor J:
I am not familiar with the finish you plan to spray, however, do you know if the linseed oil is boiled linseed or raw linseed? Boiled linseed oil has metallic driers added to help speed up the drying process. In my work I allow it to dry for several days before applying a film finish and have never had a problem. If however you are dealing with raw linseed oil it will never completely dry and will seep to the surface in warm weather and can cause problems with film finishes.

I've had luck wiping the oiled areas with a solvent soaked cloth to both remove the surface oil and to perhaps (I'm not a chemist so folks who know more please chime in) add a bit of drying agent to the outer oil to keep the raw oil from migrating to the surface. I have not had very much opportunity to try to apply a film coating over raw linseed oil but the one case where I did it seems to be working, at least I've never heard from the client who asked me to refinish her lovingly oiled dining table.

From the original questioner:
Yes it is boiled linseed oil and I have used it in the past and would spray a coat of de-waxed shellac and then pre-cat lacquer. I just started using conversion varnish and was wondering how that would behave over the linseed oil. The linseed oil has been drying for about six days now.

From contributor G:
Use that de-waxed shellac first, or vinyl sealer before CV.

From Paul Snyder, forum technical advisor:
You should be okay. If you wet the wood with BLO and wipe the excess it will dry in a day in most cases. If it's cold, humid, and dark it can take longer (sometimes days). You can tell if it's dry by the smell and feel, though it takes practice to know for sure. You can add a small amount of Japan Drier to the oil to help it dry. It only takes a few fluid ounces per gallon and the oil will always dry in a day or two as long as you wipe the excess.

If in doubt, use a catalyzed vinyl sealer for the first coat of finish. Not only will you overall finish be more resistant to damage from water/moisture, but you will ensure that the topcoats have good adhesion. Make sure the vinyl sealer is catalyzed so the second coat of CV doesn't wrinkle.

From contributor K:
If it is dry it will work. If not it will peel off later or lift on the second coat. Thin your sealer coat of cv 20% with lacquer thinner to allow a deeper soak of the sealer and let the sealer dry overnight.