Wood stains may be divided into (a) Water stains, mixtures of dyes or pigments with water; (b) Spirit stains, having the colouring matter dissolved in turpentine or alcohol; (c) Oil stains, in which the pigments are mixed with linseed oil and turpentine; and (d) Chemical stains, which change the colour of wood by chemical action.
Water Stains are very popular, being transparent and allowing the grain of the wood to be displayed; and cheap. The colours, ready for mixing with water, can be purch vsed at an oil shop. They roughen the surface of the wood, however, unless precautions are taken beforehand as follows: Damp the wood all over. The uneven swelling of the fibres roughens the wood, which, when quite dry, is rubbed smooth with fine glass-paper. The process may well be repeated to make it certain that the grain will not come up when the water stain is applied.
The pores of the wood are then plugged by rubbing in a mixture of plaster-of-paris whiting, and water, smoothed down afterwards with fine sand-paper used along the grain. End-grain surfaces should be well sized.
When applying the stain, keep the brush well charged and do not retouch a surface that is partly dry. Wipe oil any surplus quickly with a dry rjg. If the shade is not dark enough, a second coat can be applied, or light patches dealt with locally. As a general rule it is safer to reach the desired shade in two or three stages with a weak stain than to depend on a single coating of strong stain.
When the stain is thoroughly dry, rub down with brown paper, size the wood, allow it to dry, and apply a second size coat. Then rub down and leave the work to dry a few days before varnishing. Any moisture left in the wood will mako varnish turn cloudy.
Spirit Stains are much more expensive than water stains, and therefore more suitable for high-class work. They do not bring up the grain, and are more easily controlled than water stains, as they do not penetrate the wood BO quickly.
Oil Stains also do not bring up the grain. They are better than water stains on rough and porous wood, being less penetrating. The higher the proportion of oil to turpentine the smaller will the soakage be.
A solution of bichro-mate of potash is very useful for darkening oak and mahogany. Pyrogallic acid (1 part to 30 parts water) stains white woods grey; and the same colour is produced in oak by a 2-per-cent. Solution of sulphate of iron.