Hokay folks,
What is the Rx when faced with refinishing table tops that have been treated over the years with a commercial furniture polish/treatment that contains silicon?
The ones that are a particular bugaboo are distressed pine, so I’m not particularly enthused with the idea of a complete strip of the old finish. I’ve tried washing with mineral spirits and lacquer thinner both, both before and after scuff sanding the old (urethane) finish, but it is evident that this stuff is still there and interfering with new urethane layers.
Any thoughts, or better yet, actual (positive) results?
Thanks in advance
Replies
Detergent and shellac
Thanks Steve.
I had considered both, but especially in the case of the shellac, didn't figure it would adhere any better than the varnish. Can you shed any light on why this is so?
The use of detergent should have been obvious.
I will also try some Waterlox as opposed to urethane for the top coat(s).
I'm skating on the edge of ,my knowledge here, but the shellac has different surface tension characteristics than varnish. That helps it avoid pullng away from the silicone created "slick". (In other contexts it can cause problems, such as the "fat edge"--the little ridge you can get on sharp corners when using shellac.) Shellac is the commonly recommended solution and is certainly worth a try. Spraying it on helps contain the silicone, that if brushed might become mechanically mixed into the shellac.
Thanks again Steve
Thin ice is better than deep water I guess......
About what I figured w/ spraying the shellac.
Just got a new delivery of basket cases, so I'll be trying the various solutions on this batch. I'll know immediately if things are better as soon as I try applying final top coats.
I'll post results for anyone interested.
If you have to remove the prior finish, it is best to use a chemical paint stripper containing methylene chloride. A paint stripper does not remove much or any of the patina. Do it twice. Now wipe the surface down with acetone or laquer thinner keeping a fresh face on your paper towel for each stroke. Do it again. Now you can apply a pigment type stain. Follow this with a sprayed on coat of dewaxed shellac. For the tables I have done, I buy a couple of spray cans of Zinnser Spray Can shellac. It's totally dewaxed. Apply two coats and do not sand between or after the coats.
I much prefer a non-poly varnish but you can use a poly varnish too. Apply the first coat thinned about 20%. Let it dry and very lightly sand the surface with 320 paper on a felt covered or rubber sanding block. Sand in the direction of the grain and be very gentle. If you sand through the varnish, you may have compromized the shellac barrier coat. Apply a second full strength coat and you can sand a little more aggressively. Apply at least one more coat.
Some results
Thanks, Howie, for your input.
What I have gotten out of this is the use of sprayed shellac to lock in stain and residual silicon contamination.
What I have found, however, at least on the most recent set (3) of tabletops, is that spray alone is not sufficient.
These tops required chemical stripping followed by aggressive sanding to remove the scars. Thus no patina issues to worry about - wood is birch - white (paper), I think, no less, with a cheesy cherry stain - they're more orange than anything else.....what patina?!
After the stain dried, I sprayed what I thought were 2 pretty thick coats of shellac, the second perhaps 1/2 hr after the first. I then tried to varnish, but no go: terrible results. Very discouraging. Washed off the varnish w/ thinner, let 'em dry for a time while I went on to other things and let my thoughts percolate.
I figured I could go in one of two directions from there. A) my can of Waterlox was possibly compromised, and I could try a new can of poly, a fresh can of Waterlox not being available, or B) I could brush on an uncut coat of shellac over the sprayed layer, and try again.
Mostly because I really wanted to use the Waterlox, I decided to try option B first. It worked. I washed off any residual thinner w/ detergent solution, wiped dry, waited a bit and went at them w/ Sealcoat, full strength. The spray layer(s) gave enough base so that the brush coat went on easily, no wrinkling or fish eyes evident. A light scuff w/320 grit, and the Waterlox followed with equally pleasing results.
Now have 2 coats on, hope to put on a final coat of the satin finish tomorrow.
All in all, despite a good final result, a ridiculous amount of fussing to get there, even considering that the learning curve has been largely negotiated, at least for this round. I'm now trying to figure out the best avenue to get our housekeepers to change products.
Even if I can succeed at that, though, there are literally hundreds of wood surfaces that I might see in the future that are already contaminated. Yippee.
Glad to see you have made the progress you have. Silicone contamination is a weird thing. Some times it cleans up easily but I have seen times when you never get it thoroughly cleaned up. In those cases, the only option is to try a "fish eye remover". The problem with this is that fish eye remover is itself pure silicone. The idea is that you effectively create a single large fisheye so you don't see individual defects. But, it contaminates all your equipment and, if sprayed, it contaminates all the items in your shop including stored wood.
I have found that the wipe down with acetone or lacquer thinner is important.
This is a VERY COMMON problem... also a pretty vexing one! I have dealt with this numerous times and also consulted with all manner of experts or pseudo experts. The best solutions I have come by are to use a hand rubbed finish or to spray finish with several coats of fog spray followed by standard topcoats kept to thin applications.
For the hand rubbed solutions I use my own mix of polyurethane and thinners with a bit of raw linseed added. This can vary quite a bit in exact recipe but is not critical except that it be workable on the particular project at hand. The advantage is that the finish is already getting sticky when you quit the hand rubbing and there is so little flow-out potential left in the coats that they are unable to respond to the residual silicones by flowing away to create pits. Disadvantages are that this finish takes time, a lot of rubbing, significant skill and/or practice.
For the spray fogged coats you can use any clear finish (and even tinted ones though due to the nature of these type applications tinted coats tend to obscure grain patterns). By fogging the finish you do not allow it to build to a depth which allows flow-out to begin... thus the finish cannot react to residual silicones by creating pits. The key to fine work in this style is to run right at the edge so that your finish is as nearly clear as practicable but not pitted. When the finish is too coarsely divided into individual droplets it will tend toward cloudiness and obscurity. Advantages are fast work even over large areas, quite excellent consistency possible and good protection. Disadvantages are less clarity of finish (compared to hand rubbed finish above and also to standard spray applications) and the need for quality spray equipment.
As you can see the key to solving this type of problem is to defeat the finishes ability to flow away from the silicones by severely limiting it's free flowing opportunities. All sorts of washing solutions are simply wastes of time as they have almost non-existent success rates. Anti-fish-eye additives have some potential for success but are not nearly as reliable as these two strategies I have outlined.
nampa:
Thanks for the input. VERY COMMON is certainly true in my case (see above post).
Should (when?) I run into this again, with a piece of fine furniture, I'll be keeping your "hand rubbed" alternative in mind.
At present, I'm dealing with very pedestrian stuff, and lots of it, and the shellac spray coats/shellac brush coat/varnish coats regimen is working well.
What probably won't work so well is the effort to discontinue the use of the offending product.......after all, it's not their problem. And the fact that they are creating problems for others probably won't hold much water.
Seems to be the way of the world, n'est pas?
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