Tips on Using Chemicals for Finishing

Tips on Using Chemicals for Finishing

Tips for how to correctly use chemicals in the woodworking finishing process.

Craftsman Style

¶ There are a number of general points to keep in mind when using chemical stains and of course nothing but experience will teach the wood finisher to become expert in their use. The following are of interest in that connection, however.

¶ Some of the chemicals used for stains, those which come in dry crystals or hard granular form, like permanganate of potash, should be dissolved first in a small quantity of water and later diluted to the desired strength for the color wanted. Other chemicals which come in the liquid form, or readily dissolved soft crystals., can be dissolved and diluted at the same time. Nitric acid is one of the chemicals in this class.

¶ The chemical stains as a class penetrate deeper than any other class of stains. When used hot they penetrate deeper than when used cold. And when the wood being stained contains naturally some of the same chemicals as constitute the stain the stain goes into the wood even deeper yet. It is well to keep in mind that man does not create acids and alkalies. The chemist doesn't create anything, he simply separates and concentrates acids and alkalies from other substances. For instance, one of the stain chemicals much used is tannic acid. It is a chemical concentrated and separated by chemists from oak bark and gallnuts, from a vegetable substance called tannin. Most of the lumber contains tannic acid, some a larger amount than others. It is all quite simple and very interesting, yet most of us not being chemists fear what we do not understand. We might profitably understand much more of chemistry, which is so interwoven with life that we meet it at every turn, if we would but pursue the subject a little more.

¶ The aniline stains produce their final color on wood rather quickly, but the acid and alkaline stains, depending as they do upon chemical reactions in the wood, develop slowly and continue to change color for hours.

¶ Twenty-four hours or more are required by chemical stains to reach their final color.

¶ The use of chemical stains by a novice is a little uncertain at first because it is not easy to determine how strong to make the chemical solution to produce the color wanted. The furniture finisher finds this no disadvantage in the factory because he usually has a great many pieces of furniture to finish alike and he makes up a few samples on the kind of wood used in the furniture and after a little experimenting he is able to measure his chemical solution, as to its ingredients, by weight, so that he knows exactly what the stain solution is going to do before he puts it on the surfaces to be stained. The wood finisher of houses can do the same thing often, but not always, and if the surface to be stained amounts to but a few pieces, he will waste his time with chemical stains, unless cost is no consideration in producing certain color effects which can only be done with chemical stains.

¶ The chemical stains as a rule dry a much darker color than the wet color indicates.

¶ In the use of both chemical acid and alkaline solutions as stains on one job do not mix them together as a rule because one will neutralize the other, in part at least. The common use of these solutions is to put on one and let it dry before the other is put on. The color which results is due to a chemical action of the two solutions and the chemicals in the wood.

¶ The water used for mixing water stains of any kind is best when it has been boiled, distilled, or rain water carefully filtered.

¶ The colors produced by chemical stains are the most permanent known, usually, because they are natural chemical changes in the wood and they penetrate deeply.

¶ Chemical stains may be applied with an old bristle brush or a fibre brush of the zampico type. The weaker solutions are sometimes put on with a sponge. The sponge should be soaked in the solution and squeezed out before the surface is rubbed over with it.

¶ Chemical stains should be mixed and stored in glass or earthenware jugs and kept corked tightly when not in use. Some chemicals destroy tin or other metal containers.

¶ When chemicals are stored for use later they should be kept in dry places, that is the chemicals which come in dry powder, lump or granular form. Some absorb moisture and some give off moisture. They change in physical form, from dry to liquid, in some instances when moisture is present in the air. The temperature of the store room should be about 40 or 50 degrees and dry. Carbonate of potash, for instance, in the dry crystal form will change to liquid in the presence of moisture in the air. Then you don't know how strong one ounce of it is as compared with an ounce of the original dry powder; and what the first ounce did in the way of coloring wood is no indication, then, of what the second ounce will do. And again, sulphate of iron (green vitriol or copperas) comes in green, granular shaped particles. If not kept sealed up in the presence of moist air the little green lumps become coated with a gray powder and the grayish lumps do not weigh as much as they did at first So to protect the coloring strength of chemicals store them properly.

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