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Home & Garden Articles
Helpful Information About Using and Storing Shellac
Sat 30 May 2009 - 07:14
Helpful Information About Using and Storing Shellac
By [http://ezinearticles.com/?expert=Allison_Ryan]Allison Ryan
Liquid shellac, as prepared by the manufacturers, does not keep well in metal cans. After a few months, shellac that is kept in metal cans will gradually darken. This discoloration, especially in the case of white shellac, becomes serious after two or three years, and can always be noticed in the contents of a tin can that has been opened but not used promptly. The darker colors can sometimes be balanced out by the addition of a minuscule amount of white crystals of oxalic acid to the shellac mixture.
The use of oxalic acid in shellac-varnish is a very questionable practice, however. If too much is added, the acid may bleach the stain under the shellac, or lighten the tone of the wood itself. This will cause parts of the furniture to appear inconsistent, especially on the bar rail molding, an everyday object, or the wooden bar rails themselves. An expensive or finely made cherry bar rail can also suffer from too much acid content in the shellac. Some manufacturers store their product in glass bottles in order to prevent discoloration.
Experts recommend that prepared shellac varnish be kept away from strong light. It should also be stored in a reasonably warm room during cold weather, in order to prevent settling of the resin. If a can or bottle of shellac is not kept tightly corked, the alcohol will rapidly evaporate into the air, causing the contents of the can to coagulate. After a time, the thickened residue cannot be thinned in such a way that the solution will spread properly under a brush. The most serious trouble that comes from leaving a can of shellac open comes from dust, which can settle into the mixture.
Every speck of dust that goes into an open can of either shellac or varnish means a speck in a finish after it is applied to a surface and this speck can never be removed. Shellac varnish that has stood open in a room for any great length of time is always ruined for wood finishing It is also ill practice to store shellac in heated places like fireplaces and fireplace mantels, even if the unique fireplace design requires it. The alcohol in the shellac is highly flammable. Shellac dries hard, usually in about eight hours, and is ready for sanding with fine sandpaper.
While two coats of shellac can probably be put on during one day, it is best that a full day should elapse between applications. Great care and fine sandpaper must be used when smoothing and cutting off the gloss of shellac films, especially when thin mixtures have been applied. If both the shellac coat and the stain are cut through by careless sanding, it is very difficult to make a repair that will not show. An inexperienced finisher can do more damage in a few minutes with sandpaper than an expert can repair in many hours.
Camphor gum is sometimes dissolved in liquid shellac in the proportion of one ounce of camphor to a gallon of shellac in order to make the mixture spread more easily under the brush. Small quantities of camphor gum are frequently put in spirit varnishes made of shellac, sandarac, and mastic cut in alcohol. This might be useful for wall guards and old wooden [http://www.ferche.com/products/mantel-kits]corner guards, as they are scuffed up against corner guards for furniture and need to be refinished quite often. Damp weather may cause trouble when spreading shellac because of the affinity of alcohol for water.
If the film has a greenish hue or showing a turbid, cloudy appearance, the finisher should stop work until conditions are suitable. The shop windows should be closed during rainy weather. If the room is too cold, shellac will not spread well. Thin shellac varnish will, however, spread better in damp weather than will a thicker mixture. The effect of humid air on shellac can usually be seen if a finisher attempts to spread bleached or white shellac varnish over a dark-colored wood, such as walnut, during damp weather. This is also more noticeable on a more artistic project, such as a carved chair handle or professionally made ornamental pediment.
As many decorative wooden trunks are also pieces of art, it is a good idea to wait for the right weather before undertaking such a project. The shellac film is apt to turn white or yellowish white, as the rapid evaporation of the alcohol changes the temperature of the surface enough to cause moisture to condense and leave light streaks where the brush has applied the shellac. As soon as the water in the film dries out, the proper color is almost always restored. If white shellac is mixed with a small amount of orange shellac, or slightly colored with a spirit dye, the discoloration from moisture is greatly reduced.
Allison Ryan is a freelance marketing writer from San Diego, CA. She specializes in do-it-yourself home improvement from fireplace mantels and wooden bar rails to ornamental pediment and installing corner guards. Stop by http://www.ferche.com/ for the best in the hardwood moulding industry.
Article Source: http://EzineArticles.com/?expert=Allison_Ryan http://EzineArticles.com/?Helpful-Information-About-Using-and-Storing-Shellac&id=2410205
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