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The truth behind craters and ridges.
IIf your finishing career has been limited to completing the projects you have done, you may never have experienced fish eye. But if you’ve done a lot of finishing, especially furniture, you’ve definitely seen the fish eye.
Fish eye is the finish that crawls upward to form moon-like craters or ridges in seconds after brushing or spraying a top coat. You can actually see the finishing move. The cause is almost always silicone contamination, so the first thing to understand is silicone and how it settles on furniture.
Silicone is a synthetic material composed of silicon (sand), oxygen, carbon, hydrogen and additional elements to create a liquid, gel, resin or hard plastic. Surely you are familiar with silicone and may have heard of silicone breast implants.
It is liquid silicone that interests us here because many furniture polishes, especially those packaged in aerosols, contain silicone. It is a very thin oil, considerably more fluid than mineral oil when compared by placing a drop between your thumb and finger and rubbing them together. It is also totally inert, so it doesn’t damage anything.
If the silicone goes through a finish and penetrates the wood, for example through a crack or rub, it will enter the pores and create a very slippery area with such low surface tension that most new finishes will peel off. This is what causes fish eyes.
Fish eyes can also occur on new wood projects. For example, you may be using a hand lotion that contains silicone, or you may have sprayed a silicone furniture polish or lubricant near the wood you are finishing.
Silicone and finishing
When I started finishing furniture in the mid 70’s, I met the fish eye, of course. I was told by other body builders, product suppliers, antique dealers, etc., that the culprit was Pledge and that I had to discourage people from using Pledge. I obeyed diligently.
I was also told that Pledge made the finishes soften and become sticky, harden and crack (the reverse!) And that the Pledge finishes scratched (the silicone), among other problems. But I would go into people’s homes and see dining tables that had been Pledge treated for many decades and still looked great. I began to question what I was being told.
Slowly, I realized what was happening. Finishes can soften and become sticky on contact with acids (body oils) or alkalis (cleaning products). They can become hard, brittle, and simply break with age, which can be accelerated by sunlight through a window. And they can get scratched from contact with all kinds of objects.
In other words, there are accurate explanations, but a coachbuilder without this information only knew what he had heard through the gossip. So the obvious question for the homeowner was, “Have you ever used Pledge?” The answer was almost always “Yes” because Pledge had a 60% market share. This just confirmed that Pledge must be the culprit.
Why are silicone furniture polishes so popular even though many people have heard that they shouldn’t be used? Because silicone does not evaporate as quickly as petroleum distillate solvents in other furniture polishes. The oiliness provides shine for a week or two.
It also provides scratch resistance while it lasts, so furniture retains its near-new look much longer. And silicone has a low refractive index, so the wood of a table looks deeper and richer when viewed from a low angle.
Consumers love these nail polishes despite their bad reputation. It has created a dilemma for manufacturers who cannot brag about the silicone included in their containers. Instead, they brag when they don’t contain silicone, “it doesn’t contain silicone”, as if that’s a good thing.
Body builders and others discourage the use of silicone polishes (grouped together as “Pledge”), but the battle is lost. Perhaps up to 90 percent of all furniture polishes contain silicone. We just have to learn to deal with it.
The first step is to identify the potential for the fish eye before it happens.
If you are using a scrub, you should see fish eye develop immediately after a wet application. It disappears, of course, when the excess is removed because a thickness must remain for the finish to crawl. If you’re not using a stain, you can apply a damp coat of white spirit (paint thinner) or water to see if fish eye appears.
If the test is positive for silicone, there are three main ways to approach it:
1. Remove the silicone from the wood
2. Apply a sealant layer of shellac
3. Add the fish-eye eliminator to the finish.
Silicone is oil, so it can be removed by washing many times with a solvent such as naphtha, mineral spirits, acetone, or lacquer thinner. It can also be emulsified with an alkali such as household ammonia or trisodium phosphate (TSP) and water, then washed off with water. (The downside, of course, is that water will increase the grain.)
Shellac is not affected by silicone unless the contamination is really severe, so shellac can be used as a sealant under another finish. If shellac doesn’t provide a sufficient barrier, combine it with one or two of the other methods.
If you’re running out of lacquer or varnish (oil-based polyurethane), add a dropper or two of fish eye eliminator to a quart and mix well. With the paint, dilute the eliminator with white spirit first so that it mixes more easily. The fish-eye eliminator itself is silicone, so it lowers the surface tension of the finish just enough to level it well. After adding the eliminator to one hand, you need to add it to all hands.
A fourth, more difficult, method of treating fish eye is to spray many layers of paint to get a texture, then spray a layer moist enough to dissolve the dust but not so wet as to dissolve and cause fish eye. . This will take practice to get the correct result, but it works.
If you don’t discover the fish eye problem until you’ve already applied a coat or two of the finish, it’s best to remove the finish and start over, using one or more of the previous steps. You can also try to build some dusters and sand until you reach the level, but this is difficult.
Worst case: remove everything and start over.
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