Preparing a Rubbed Through Spot.—Regardless of the size of a spot, it will be much larger before your patch is finished by reason of feathering out the edges before frenching or spraying. If working on a varnished surface, the problem will be somewhat easier, especially the staining operation. Prepare the spot for frenching by sanding out the edges with 5/0 garnet paper and oil. On flat surfaces, vising a felt or cork block, sand until the edges are not perceptible by passing the hand over the spot. To insure a perfect job, sand out the edges of the spot at first with the hand, using 6/0 garnet paper for finishing up.
If working on a lacquered surface (not decorative) and desire to have the same finish on the spot as the entire surface, in other words, if you intend to spray a coat of lacquer over the spot, it will be necessary to feather out the edges of the spot with 5/0 or 6 0 garnet paper without oil and clean off well before staining.
Staining the Spot Before Spraying.—It is far more difficult to stain a spot before applying the finishing coat, unless you happen to have some of the original stain that was used, than staining the spot after it has been built up level with the surface. Previous staining is necessary before spraying lacquer to have the best kind of a finished job.
Water stain, applied with a brush, was the method formerly used, but this method is too difficult unless the original stain can be had in the same formula as used on the piece. It is best to use some kind of frenching material, as shellac, French varnish, or amalgamater, and french the spot to some extent after sanding and then apply the stain to the spot with the finger, as directed in Chapter IV. In this way a perfect match is made with the spirit stain, whereas if water stain in uncertain proportions is used the guess may he incorrect. The spraying is done after the spot has been stained and rubbed -with steel wool, after allowing two hours to dry.
Spraying a Fubbed Through Spot.—All dust and pieces of steel wool must be wiped off with a tack rag before spraying. Remember that a spray should not be used in patching except on lacquer, enamel or decorated surfaces. Varnish or shellac surfaces can always be French polished much easier.
First fill the cup with the proper material, in this case, clear nitro-cellulose lacquer, especially made for spray use. Start the spray and keep up a good pressure all the time, as a low pressure allows the material to fall on the surface in small drops. Of course a very high pressure will allow a waste of material and a "dusty" surface, so a pressure of about forty pounds is the minimum.