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Expert's Corner — wetting

Water Warps Wood Opposite From What You May Think

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Water causes wood to swell, so most people think that wetting one side and not the other will cause the wetted side to bow – that is, increase in width so the center is higher than the edges. If the wood is thin enough, this will be the case initially. But the overall swelling or shrinking after many wettings and dryings out, no matter the thickness of the wood, will be the opposite. The wetted side will shrink and the wood, or boards, will cup. The four accompanying pictures show examples of this. With a little thought, you will most...

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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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TIP: Wash Off Stripper Wax

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Directions on cans of paint-and-varnish remover instruct to “neutralize” the stripper as a final step. This is misleading and often leads to finishing problems. The instruction is misleading because there is nothing in paint strippers that needs to be neutralized. “Neutralizing” refers to acids and bases, not solvents. What needs to be done with all paint strippers sold in metal cans is remove the wax they contain. Manufacturers add wax to these products to retard evaporation so the stripper remains in contact with the paint or finish longer. This wax will retard the drying and weaken the bonding of most...

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