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Expert's Corner — blotching

TIP: Use Wood Conditioner to Reduce Blotching in Softwoods

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TIP: Use Wood Conditioner to Reduce Blotching in Softwoods

Products sold as wood conditioner are washcoats usually made from varnish, though I have seen at least one that is an oil/varnish blend. A washcoat is a finish thinned to five-to-ten percent solids with the appropriate thinner. (Finishes are generally supplied with 20-to-30 percent solids.) In industry, the finish used is usually lacquer thinned with lacquer thinner. Wood conditioners can be fairly effective on softwoods like the pine shown in the accompanying picture. They aren’t as effective on hardwoods such as cherry. The purpose of the thinned-finish conditioner is to partially seal the wood, which means to partially stop up...

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TIP: Grain Reversal in Stained Pine

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TIP: Grain Reversal in Stained Pine

Pine is often stained to make it resemble a higher quality wood such as walnut, cherry or mahogany. You need to be aware, however, that the staining reverses the grain color, making what was the lighter-colored grain now the darker-colored grain. This happens because the softer, lighter-colored grain absorbs more of the stain than the much harder and denser darker-colored grain. An example of this is shown in the first accompanying picture. The left side has been finished with a clear finish. The right side has been stained and finished. The only way to keep this from happening is to spray the...

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TIP: Make Cherry Look Old

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TIP: Make Cherry Look Old

One of the great unknowns commonly pursued by woodworkers is how to make new cherry look old without any blotching. Here’s a discussion. The rust-red coloring in old cherry develops over many decades from oxidation accelerated by UV light­­—and possibly also by an original application of linseed oil that has darkened. You can get part way to this coloring by exposing cherry to sunlight, but only part way. You can also get part way by applying boiled linseed oil, and the wood will darken more as it ages. But to get all the way, you have to use a dye...

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Wetting to Predict Blotching

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Wetting to Predict Blotching

You can usually get a pretty good idea whether or not the wood you are using will blotch when a stain or finish is applied by wetting the wood. You can use any liquid, but water will raise the grain causing you to have to sand more. Mineral spirits (paint thinner) works well except if you intend to apply a water-based finish. Some residue oiliness may remain and cause the finish to fish eye—that is, bunch up into ridges rather than level out. Denatured alcohol would be better for this situation because it will totally evaporate. But it evaporates quickly,...

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