Woodworker's Journal 2011-35-Winter, страница 34
Bleaching Wood: Staining In Reverse Chemical options for lightening wood color and erasing stains. Staining means adding color to wood. Bleaching, its logical opposite, is the process of chemically removing color from wood. You can remove accidental stains, intentional (but ill-advised) wood dyes, or the original colors that nature placed in wood, using one of three basic bleaches. Here's a description of each, a guide on how to mix and use them and an explanation of what they will do. Safety and Use Guidelines All these bleaches are water-based, and all finishes repel water. Hence, all bleaching must be done on raw (unsealed) wood. If you're trying to remove a stain from a finished piece of furniture, you must strip the finish first. It's also a good idea to lightly sand the wood to make sure the bleach can easily penetrate it More important, these bleaches are either acids or bases, and as such are reactive. That means they can harm us, so use gloves and goggles, and work in a well-ventilated room. Any gloves will do, but don't get these bleaches on your skin. You might also want to wear a vinyl apron, or choose clothes you are ready to abandon. Bleaches eat cloth and natural bristles, so apply them with synthetic bristle brushes or nylon abrasive pads (such as Editor in chief Rob Johnstone is dressed for success — which means safety when using bleaching products. These chemicals can clean up your wood, but they're also caustic.
Scotch-Brite"). Always apply bleach to the entire surface of the wood, not just the area with the stain. "Spot" bleaching can cause permanent watermarks or hard-to-blend light spots in the wood. Typically, you allow the bleach to work until it dries, but you can stop the bleaching action at any time by diluting the surface with plenty of clean water. Because it contains water, bleaching raises the grain of wood, so plan on sanding with 320- or 400-grit paper once the wood dries. Laundry Bleach Old-fashioned chlorine laundry bleach, or sodium hypochlorite, will remove many accidental stains as well as most wood dyes. However, it will not substantially change the color of wood itself. For that reason, it is a great tool for "erasing" dye stain, either on new wood or old dyes on stripped pieces. Think of it as the "undo" button. It won't remove pigment stains, but it will remove a wide variety of common food and drink stains, some dye-based inks and felt-tip markers. Laundry bleach is sold in a 5% or 6% solution, so use it straight from the container. Opened containers of bleach get weaker with time, so buy a new bottle for stain removal. If you need a stronger solution, you can mix your own using swimming pool chlorine (typically calcium hypochlorite) mixed in water. These dry 34 Bleaching Wood: Staining In Reverse |
