There are three types of stains used for woodwork finishing - acid or water stains, penetrating or spirit stains, and pigment or oil stains. The first type is generally used by piano and furniture manufacturers because of its permanency. Acid stains are designed for hard woods only, and as they raise the grain and therefore require to be sanded smooth again before finishing, many prefer to use the spirit stains, which do not raise the grain. Spirit stains may be used on both hard and soft woods. Oil or pigment stains require the wiping off of the surplus stain, but this disadvantage is offset, in the opinion of many, by one's ability to govern the depth to which the stain shall penetrate. In all cases, in staining, follow the directions given on the package as to how to reduce and apply each stain. These stains are all indicated to be used over the new wood, before the wood is filled.
Most stains require sealing with shellac before varnishing or waxing. This is done to prevent the stain "bleeding" into these finishing coats. As a rule, pure-white shellac is to be recommended, as it does not change the color of the stain as does orange shellac. A very thin coat of shellac should be applied (shellac reduced with denatured alcohol) and, with open-grain woods, may follow or precede the application of the paste filler as directed on the package in each case.
As previously indicated, open-grain woods require the use of a paste filler to level the surface for a varnish finish. These fillers come in paste form and are thinned with benzine to the consistency of heavy cream. They may be had in several colors. The so-called transparent, or natural filler, is intended for use for natural wood finishes. Some of the darker fillers contain a considerable amount of dye and really stain the wood to a degree. For light finishes some contractors effect a short cut by filling and staining the wood in one operation instead of two, depending upon the filler for the coloration of the wood. Of course where only light tints are to be applied to the wood. Such effects as antique mahogany and others need the full strength of the separate stain coat. A word about liquid fillers: A liquid filler is usually a quick-drying varnish or shellac with a pigment in it.
A word about liquid stain fillers. A liquid stain filler is usually a quick-drying varnish or shellac with a pigment in it. Whereas a paste filler actually goes into the pores and fills them, the liquid merely forms a shell or crust over the wood without actually filling it. Being brittle, this material chips off under service, and, of course, brings the finishing coats with it.
The application of the paste filler is as follows: After thinning to brushing consistency with benzine, brush it over the entire surface, and when the material has begun to set (indicated by a partial flatting out of the gloss), wipe off. First rub across the grain with burlap or coarse cloth, forcing the filler into the pores through it, and then wipe the wood clean by rubbing with a clean soft cloth, with the grain. Paste filler should be permitted to dry two days before applying the finishing coats. On all woodwork trim, this filler should be followed by a thin coat of shellac. When this is hard, sandpaper lightly with No. 0000 sandpaper. It may then be waxed.