Problems of the finishing room

The cordial reception by wood finishers generally afforded the previous editions of Problems of the Finishing Room, has influenced the author to revise and enlarge the old publication—hence in this edition will be found much information not contained in the first four editions of this book. The additions comprise many of the finishes developed within the past two years, together with a description of the new materials involved. The formulas which are offered have all passed their experimental stage. The methods are practical, the results positive. In commending them to the wood finisher, confidence is expressed that many a difficulty will have been overcome for him. Inasmuch as business conditions, and particularly those relating to all branches of chemistry and allied arts, are unsettled and unstable, it should be understood by the reader that all prices quoted in this volume are such as would likely prevail in normal times. While the author has gone much into detail in the following pages, he calls attention to the constantly increasing number of stain and finishing possibilities that are coming out from time to time. The reader is commended to the pages of the Furniture Manufacturer and Artisan in future numbers for many notes and formulas which may be incorporated in the blank pages in this book, by means of which he can keep up to the minute in finishing problems.

Wood staining not only requires the production of a stain, and the application of the various stain solutions, but the rational application of stain and a certain amount of knowledge of the different woods in regard to their adaptability and susceptibility toward a certain stain. With one and the same stain different results are obtained when applied to various woods. This is due to the very different chemical constituency of woods, which tannin or tannic acid, which is present in larger or smaller quantities, produces on many of the stains, chemical action varying in results according to the quantity of this chemical present.

Two examples will explain: First, in applying a solution of two ounces of bichromate of potash in a half gallon of water to a species of wood, such as pine, or similar wood which contains a very small amount of tannin, the result will be that of a light yellow due to the chrome bichromate, which unfortunately is not fast to light, and, therefore, in this case is worthless. On the contrary, if you take the same bichromate of potash solution and apply it to any of the oaks, which are rich in tannin, the results will be a yellow brown color, comparatively permanent when subjected to light or air. This is due to the fact that the tannic acid present unites with the bichromate, forming a brown color material. Similar effects are to be had when this bichromate solution is applied to mahogany or black walnut, as both of these woods contain considerable tannin.

Second, stain whitewood or any wood in which the tannin is practically absent with a solution of sulphate of iron, one ounce, water one gallon, the result will be negative. However, if the same solution should be applied to ash, oak or even maple, a gray color will be produced and on the oak it is very often possible to get the dark blue grays verging into black. This is obtained from the fact that sulphate of iron, or in fact, any salt of iron, when subjected to the action of tannic acid produces tannate of iron, which is the color-giving result of the procedure.

The different textures of the woods, designated hard and soft, have a good deal to do with the results obtained by the application of the stain. In a closely grained wood of a hard texture the penetration of the stain is retarded, when on the contrary large-pored wood absorbs more stain, much quicker, with the result that an ordinary application of one stain on the two different kinds of wood will produce vastly different results. If one wishes to match the hardwood with that of a soft, it will be necessary to increase the strength of the stain, which is far preferable to the possible application of several coats of stain. In case of matching the hardwood by staining a soft wood, the stain will have to be reduced in proportion. This is recommended only after repeated tests have been made. A porous wood might give indications of being dry, and as tests are usually hurried the operator is apt to fool himself and to find later the results are too dark.

A certain stain applied to a certain species of wood may not always give identical results, and in consequence the operator must be continually on his guard, as various growths and various localities will affect the stain with enough difference to manifest itself in the color produced. A thorough operator soon becomes aware of these peculiarities, and by applying the stain heavier or lighter he will succeed fairly well in holding to a uniformity of shade. Extreme cases, of course, need individual attention.

Woods containing a great deal of sap, or resinous matter, present their difficulties especially when water stains are employed, but as they are not much employed in good furniture and as we have already touched upon the handling of the stain, it will suffice to say that occasional resinous portions that are met in cabinet woods are better individually treated. Where stains depend upon the presence of a certain quantity of tannin, the formula usually employed is built up so that the minimum amount of tannin present will suffice to make the color desired; otherwise the application of tannin is resorted to.

It may be said that stains consisting entirely of the aniline dyes, in solution, reach their final shade much sooner, and with much more uniformity, than those which are made up of combinations of dyes and chemicals. It may be stated as universally true, that where chemicals are employed, some sort of chemical reaction is relied upon to produce the desired color. Therefore, it will be seen readily that when the material to be stained is not always alike, although the same kind of wood, yet of sufficient difference in its physical constituency to make possible slight variance, from 24 to 48 hours are required for the complete chemical reaction.

Stains containing chemicals should be permitted to dry from 24 to 48 hours in normal temperature, in rooms that have a good circulation of air. Whatever chemical changes are to take place will have been completely consummated within this lapse of time.

Where more than one coat of stain is required to produce certain colors, it is always best to allow at least 24 hours between each coat. Sand the first coat after it is thoroughly dry, and then apply the second coat. This is just as essential, whether the stain is made up of anilines or chemicals, the desire always being to produce a stain that is permanent. It may be well to state again that not all color materials permit being dissolved in one vehicle without injury to one another. That the novice may thoroughly understand, and further have a method of ascertaining and recognizing the fact when any of the rules are infringed upon, the following explanation will bring out the point:

We have said there are several kinds of anilines. The acid anilines and the basic anilines, both are water soluble. The finisher, however, is unable to tell to what group they belong. It may be he has a beautiful shade of brown which has been doing his work, and he wishes to employ it in conjunction with some other colors. Not knowing that they are antagonistic, he makes his mixture which may not at once manifest the chemical change that is about to take place or is taking place. Later on, however, a precipitate which is first recognized by the turbid appearance of the solution will show that the chemical reaction which is taking place is throwing part of the color material out of solution, and the stain, therefore, has become an unstable compound. As long as any chemical reaction takes place, there is an uncertainty about the color. This, however, has a fixed and definite place as soon as the acid has been neutralized by the alkali. The chemical action ceases, but in dealing with two color compounds, where the chemicals are aniline salts we are treading on pretty thin ice in an effort to obtain a color, and, therefore, it is always best to discard any attempt at producing a stain by the use of anilines of different reactions.