Refinishing a Silicone-Contaminated Antique
Silicone-containing furniture polish residue can be a refinisher's nightmare. Here, pros discuss the problem and suggest ways to cope. March 2, 2006
Question
I’m in the process of restoring a Sheraton sewing table in walnut (maybe 175 yrs. old), and the top needs refinishing. I took off the old shellac, scraped it, and rubbed it with linseed oil and turpentine, which is what I've done for years. I let it dry overnight, started coating with 1 1/2 lb. cut orange shellac from flakes. As it dried, little round spots appeared that looked like the wood refused the finish. It got worse with every coat. I stripped it twice, scraped, sanded, and started over, and the same thing occurred. I never had this problem before. Any ideas would be welcome.
Forum Responses
(Finishing Forum)
From contributor A:
It sounds like fish-eye. The previous owner used Pledge or something else with silicone. It is hard to eliminate. Try wiping it down a few times with ammonia. Test it in a spot to make sure it doesn't color the wood.
From contributor B:
This happens all the time. Surface tension is the problem. The contaminate on the wood is causing the surface tension to be uneven, and you must even it out somehow.
From contributor A:
Most fish-eye control products are in fact bottles of silicone. When you add enough silicon to your finish it will become one big fish-eye and since it becomes the entire surface you no longer notice it anymore. The problem with using anti-fish-eye products is that it contaminates your spraying system. If you have a cup gun and you insist on using the anti-fish-eye (AFE) products, that's where I would spray it from. I don't think I would ever put AFE products into a system with pots and fluid lines. It would be very hard to clean and would contaminate your entire spraying system. I have used AFE before when I had a major problem with my neighbor spraying silicone products for detailing cars, and it worked pretty well. It took me a while to clean out my cup gun but I used plenty of ammonia and got rid of the silicone. Wiping down your project with ammonia is not that difficult and will not infect everything in the room with silicone like an AFE product can.
From contributor C:
Once it is badly contaminated with silicone, it is very difficult to refinish. The shellac that you sprayed is normally the solution, but shellac in some cases will seal in the contamination. In other cases the shellac will reactive the silicones, and then the silicone contamination comes right through the coating. If the ammonia wash, or the TSP fails, then another alternative you might want to try is sizing the wood with hide or white glue and water 50/50, as a barrier coat to seal in the silicone. I suggest that you only apply a couple of clear coats of shellac, and then quit while you’re ahead.
From contributor D:
I know silicone additives are intended to solve the fish eye problem but in my opinion they just make things worse. It takes an extremely small amount of silicone in your equipment to cause problems on the next jobs. I would only add that I've had the best results by keeping the first few coats of shellac very thin. Even after that, don't be tempted to wet things down. A wet coat will burn through the existing coats and you'll have fish eye again.
From contributor E:
We recently tried to refinish some coffee tables which probably had silicone sprayed on them for years. We tried to clean with TSP, automotive cleaner for silicone, acetone, denatured alcohol etc. We shot shellac and vinyl sealer - no good. I ended up shooting DuraVar over the messed up vinyl and then French polishing the mess with straight retarder, letting it kind of get hard and then haphazardly polishing it. If glue will stick to it then coat it with glue. One thing that might ease the pain a bit is shooting very thin coats. Another tactic we didn't have the time to try was given to me by MLC's lab - shoot undiluted vinyl and let it fish eye but then let it cure for 2 - 3 days in a good environment. Even though there are craters the vinyl may have bridged the problems and locked down the contaminant.
From contributor G:
Get a product called Smoothie. You can get it at auto paint shops. A squirt in a quart cup will do the trick. You might want to try a lacquer base finish. You’re making it a lot harder than it has to be.
From contributor H:
I agree with washing with TSP and then spraying it with undiluted Vinyl - dry spray.
From contributor C:
Smoothie is also a silicone additive, and at the stage this piece is in, it will not help. In fact, what happens is that the silicone additive you use will begin to actually repel - not adhere - to the coating.
From the original questioner:
Many thanks for all the suggestions - the more input the better. My limitation is that the piece is a somewhat valuable antique owned by a dealer. I have to approach it with conservation in mind, thus the need for a traditional finish - brushed on shellac, which was on it originally. Taking into account all the info provided by you all and others, I will try washing it down with naphtha, apply a very dilute sealer coat or two, and refinish.
From contributor C:
It’s certainly worth a try. There are some other companies that also sell silicone cleaners.
Let me just add that it is easier said than done. A lot has to do with the amount of silicone contamination on the pieces.
From contributor I:
Try padding the shellac. There is a lot of information online about French Polishing. Try padding the first couple coats, then try spraying. Otherwise, just pad all the coats and then rub it out, if your padding isn't the best.
From contributor C:
Silicone contamination is like a virus - it will spread, so padding (French polish) will only move it around. I would say from the comments that it is badly contaminated, and I would probably try stripping it again, and then washing it down with different cleaners including acetone. Be sure you turn the cloth over after each wipe, or only one wipe and change the cloth. You do not want to re-wipe the silicones back on the wood. Then dispose of the contaminated clothes. I would then try misting and fogging on the shellac to get a base, and then apply one good flow coat, allow it to dry, and then match the original sheen with your pumice. If necessary, go to the rottenstone.
From contributor I:
I have seen silicone go through several layers of finish. I don't think I have ever seen a French polish fisheye. That’s good advice for cleaning - definitely change the cloth as you wipe. Litho pads from a graphic art supply company work really well. Printers use them to clean off their print rollers with no lint residue. Xylene is also a good chemical for removing silicone.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor W:
If you removed the original or early surface coating then you are not conserving but doing a reinterpretation of the historic coating. Silicone can be a tenacious contaminate as you have found. On a molecular basis Xylene is the best solvent for removal, but the trick is in how you pull it out of the wood. If you move the solvent around on a rag then you just keep moving the silicone too. Soak it down, swipe it off with a paper towel, one stroke and throw the paper towel away. Do this over and over to wick the silicone up and pull it off. If you can't spray mist coats of your shellac then try cutting to a 1# and brush coat very thin, several coats, plenty of drying time between, to try to lock it. Sand it or use steel wool to level, and then wax it.
Comment from contributor J:
I had the silicone contaminate issue with some cabinets I was refinishing. I ultimately scrubbed the doors with zylene and then lacquer thinner before spraying a coat of shellac over the surface. Then I sprayed lacquer to finish it off and none of the craters returned.
