There are two kinds of aniline dyes - one set soluble in water, and the other soluble in spirits. Both kinds may be used for producing dye solutions, but for penetration, especially on hard woods, the alcoholic solutions are preferable, but good results can be obtained with either class of dye.
To prepare an aqueous dye solution, put one ounce of the dye into a clean earthernware pan or jar; never use a metal receptacle, nor a wooden one, because metal will react on the dye and its color, and wood will absorb some of the dye and not only thereby lessen the strength of the solution, but the wood will become so impregnated with the dye it first comes in contact with, that such vessel cannot be used for preparing a dye bath of any other color. Pour one quart of boiling hot water on to the dye and stir it up with a glass rod or wooden stick and let it settle for an hour or two; then filter the dye liquor through a plug of cotton wool inserted in the neck of a glass funnel, and store the dye liquor in clean bottles for use, not forgetting to label it with the name of the dye and its strength, such is "the strongest solution."
Now one ounce of aniline dye will generally be more than one quart of water will completely dissolve, consequently the dye that has been collected in the filter will still yield a second decoction, so remove the plug of cotton wool from the funnel and put it in a glazed jar or pan and wash all the dye that adheres to the funnel into the vessel by pouring one quart more of boiling hot water on it, and when the liquor has extracted all the coloring matter it can, filter it through a fresh, clean piece of cotton wool.
Label the second batch of dye liquor and mark its strength as being second strength, or No. 2 solution. To use these dye liquors it will be found that the first quantity of liquor obtained will be too strong to use unless it is diluted, being of concentrated strength; the dye, as it dries, will exhibit a bronzed efforesence or irridesence; therefore a little of the liquor should be taken and diluted more or less with hot water, according to the tone of color it is desired to exhibit.
In using the dye liquor of the second strength, that will not be strong enough to produce a bronzed surface, and therefore may be Used undiluted, if so desired. It is best to prepare these dye liquors in two strengths of solutions, as by that means one solution can be strengthened at any time by the addition of some of the concentrated solution.
To prepare alcoholic solutions or " tinctures " of the dye proceed as follows:
Put 1/2-oz. of the dye into a clean glass bottle and pour on it one quart of rectified spirits, or else methylated spirit (but the spirit must not be methylated with any mineral oil, such as paraffine or benzol, as these hydrocarbon fluids do not dissolve the dye); shake up the fluid several times during the first few hours, and then let it rest for 24 hours; then decant the clear fluid from the dregs. If it be filtered, a piece of clean blotting paper or filter paper should be used, and a plate or saucer placed on top of the glass funnel so as to prevent the spirit evaporatiug while filtering. The dregs or residue may be treated with a fresh portion of alcohol to produce a weaker tincture. Each of these batches of dye should be stored in closely corked bottles and labelled first and second strengths, together with the name and color of the dye.
Besides "water" and "spirit" dyes there is a new class of analine dyes, which are soluble in oils and fats. These dyes are known as "oil" dyes, and are very useful for coloring varnishes and wax compounds, but they are not so useful for staining purposes.