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Expert's Corner — sealer

TIP: A Short History of Shellac

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TIP: A Short History of Shellac

Here’s a short history of shellac, some of it from my own experience. Shellac was almost the only finish used on furniture from the 1820s to the 1920s when nitrocellulose lacquer was introduced. Shellac continued to be used widely as a complete finish by painters working in buildings until the 1950s. By the 1990s the only remaining supplier of shellac in liquid form was Zinsser, which sells the shellac under the brands “Bulls Eye,” and “SealCoat,” which is a dewaxed variety. Zinsser specializes in sealers and primers, so it markets the shellac as a sealer. The marketing strategy seems to...

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Oil Finishes and Moisture Resistance

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Oil Finishes and Moisture Resistance

Oil finishes provide very little moisture resistance. This is because oil finishes (boiled linseed oil, 100% tung oil and mixtures of oil and varnish, often sold as Danish Oil) don’t get hard, so they can’t be built up on the wood to provide a thicker moisture barrier. You have to wipe off all the excess after each coat. If you drip some water on an oil finish, the water will penetrate quickly and raise the grain of the wood, causing a smudge mark like the one pictured. If you live in a relatively humid area (not the desert), the surface...

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Primers and Sealers

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I’ve said this many times, but it deserves repeating because so much confusion still exists. Primers and sealers perform entirely different functions. Primers are necessary for paint because paint won’t bond well to rough, porous wood. Paint contains a high percentage of pigment (in order to hide well) and only enough binder (the same as finish) to glue the pigment particles to each other and to an underlying smooth surface. Because even well sanded wood is still porous, and thus not smooth, more binder is required to achieve a good bond. Paint primer contains a higher binder-to-pigment ratio than does...

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