The effect of ammonia, either the liquid or fumes, is much the same as the effect produced by aging or weathering. Ammonia also cuts the pith rays of oak and makes it possible for other stains to take hold. For this reason it is much used as a preliminary treatment for oak finishes. The color effect is to lessen the yellow and increase the gray.
The method of application is simply to expose the wood for a day or more to the fumes of strong ammonia (28%) in a tightly closed box. If the surface of the wood is moistened with water just before exposure, it turns darker than if exposed dry. The stain penetrates so deeply that it may be sandpapered after the exposure without harm. After fuming and sandpapering the surface should be oiled to prevent finger marks.
Dark brown for chestnut, or oak, or mahogany. This is obtained with a solution of acetate of iron, made as follows: digest one part by measure of iron dust in 8 parts of glacial acetic acid. After the chemical action is well started, add several times as much water to keep the mixture liquid. When the chemical action has ceased, the stain is ready for use. If a lighter shade is desired it may be still further diluted.
To darken mahogany. Make a saturate solution of bichromate of potash. Dilute a portion of it with water 1/2, or 1/3, or 1/4, or in any proportion according to the darkness required. One part of the solution to two or three parts of water gives a good color. Apply the solution to mahogany with a brush. This solution alone is likely to be too brown. The reddish tinge of the wood may be saved by mixing as follows:
100% solution of bichromate of potash 1 part Breinig's mahogany water stain 1 part Water 2 parts Apply with a brush and wipe off the surplus.
Bichromate of potash on oak gives a rich brown.
Bichromate of potash on ash gives a rich red.
Bichromate of potash on black walnut gives a dark brown.
A decoction of logwood treated with tannin gives yellow red, with sugar of lead gives gray brown, with ferric nitrate gives black. A decoction of fustic extract treated with dilute nitric acid gives brown, etc.[13]
[Footnote 13: For other effects obtained by chemical changes, see table on pp. 185-189 in _Brannt's Painter, Gilder and Varnisher_, and also _Woodcraft_ 9: 71, June, '08.]