I have recently encountered a problem with my sprayed lacquer finish process. After the final finish coats of lacquer have dried, what best can be described as an oily film appears in random patterns over the entire surface. This oily film can be removed by rubbing with your finger or a soft cloth only tho reappear several hours later.
My finishing process for cherry and walnut, after finish sanding to 220 and dusting, is to first apply a 50/50 mixture of boiled linseed oil and mineral spirits; rub off the excess oil after about 20 minutes and allow to dry 24 hours. Next I lightly sand with 0000 steel wool, dust, and apply two coats of sanding sealer, sanding after each coat with 320 paper. Allow this to dry over night and apply two final coats of “dull” lacquer. Is it possible that the linseed oil is somehow bleeding through the lacquer coats? I use ML Campbell Magnalac, sanding sealer, and thinner. This is the process that I’ve used for years with no problems, the only change has been the use of ML Campbell materials in the past I used Sherwin Williams finishing materials. Any thoughts on this problem? Thanks-Ron
Replies
my feeling would be that it is either old linseed oil or old lacquer ( stale dated) . The shelf life of the ml cambell products are one year absolute tops. But the linseed oil would be my likely culprit. Why don't you try letting the oil set for 48 or 72 hours and/or coat the substrate after the oil coat with Zinsser's Seal Coat. This is a 2lb cut of 100% wax free clear shellac that is compatable with almost anything including urethanes and lacquers. I have used this to seal in tricky old stains and then top coated with two component lacquers with no problems.
Deckerman-Thanks for your reply, in the past I always use a thinned coat of orange shellac on cherry to seal the linseed oil and add a little warm color to the cherry. I never had a problem when I used a shellac seal coat. The ML Campbell products were well within their expiration dates printed on the cans. In the future I'll go back to the shellac seal coat. Any ideas on what to do now other than letting the piece dry for several days in a warm room? I sure don't want to have to strip off the finish. Thanks-Ron
wipe the surface with Mohawk shellac thinner ( ethyl alcohol based) which is better than methyl hydrate ( which is methyl alcohol) lightly a few times in succession over a few minutes in between each wipe and then seal what you have done with the Zinnser Seal Coat. After the ethyl alcohol wipe lightly resand the piece with 400 grit or even 600 grit and then give it two VERY thin coats of the shellac to isolate the coating problems. Make sure you use the Seal Coat because if you use regular commercial shellac it has wax mixed in and that will create its own set of problems. After sealing it with Seal Coat then let it dry minimum 4 hours at 70 degrees and no more than 75% relative humidity- longer dry times if you can't meet those conditions. At this point you may now treat the piece as if it was just sealed and proceed to lacquer or whatever. Let me know if you have any problems.
Edited 12/8/2006 9:14 pm ET by deckerman
Thanks-I'll start the process today and let you know how it works-Ron
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