In very many cases where complaints are made of the poor work done by the finishers or the poor results obtained from the use of a cer tain varnish, the cause will be found to lie in the unfavorable conditions under which the work has been done. Often, before the carpen tern, plumbers, or plasterers have finished their work, the painter is urged to rush the work as fast as possible. The air is full of dust; the building is seldom heated, and the temperature is allowed to fall at night; the second coat of varnish follows as soon as the first is "set," and before it has a chance to become thoroughly dry. The carpenters seldom leave the woodwork in good condition for the painter. He finds it far from smooth and requiring both scraping and sandpapering, marred by pencil marks, dented by misdirected blows from the hammer, greasy from the fingers of plumbers and others, etc.
To do a first-class job of hardwood finishing, all the other work should be completed before the room is turned over to the finishers. The rooms should then be thoroughly swept out, and the floors sponged off or wiped off with a damp cloth and allowed to become perfectly dry. The sash should be fitted and in place, and the doors hung; and both doors and windows should be closed to prevent draughts. An even tempera ture of about 70° should be maintained night and day. Wherever possible, doors should be taken from their hinges and laid flat on a pair of trestles while varnishing, in order to flow on a more even coat. The door openings, in this case, can be closed with light frames covered with building paper or cloth to prevent dust and cold air coming into the room. Unless these precautions are taken and unless ample time is given, a first-class job of hardwood finishing is impossible.
It must be remembered that there is an im portant difference between painting and var nishing. Whereas paint should be applied in a thin coat, thoroughly brushed out with a rather stiff bristle brush in order to work it into the pores of the wood, varnish should be flowed on in a heavy coat and when applied should be allowed to level itself out. The luster and beauty of the varnish depend largely upon the depth or thickness of the film, and it naturally follows that a heavier coating can be applied to a level surface than upon a vertical one. Very few varnishes will stand crossing, but they should be applied in parallel strokes with the grain of the wood, using a wide, chisel-edged camel's hair or elastic bristle varnish brush.
There is no economy in using any but the very best brushes that can be bought.
In preparing the surface, all pencil marks must be cleaned off. Greasy stains should be removed; ammonia is excellent for this, but it requires subsequent washing off, and, since it can be used only on such woods as do not con tain tannic acid, as it darkens oak, mahogany, etc., gasoline or naphtha is probably more gen erally satisfactory. Hammer dents in the surface can sometimes be obliterated by soaking well with water and holding a heated flatiron in front of the dented spot. All plane marks must be carefully obliterated by means of steel scrapers, and finally the wood must be made perfectly smooth by means of sandpaper or steel wool. Extra care must be taken in doing this to avoid rounding off the edges of mouldings and other sharp corners. Finally, every particle of fine sand and wood dust must be carefully dusted off, and the surface left perfectly smooth and clean.
If the wood is an open-grained wood, it will need to be filled with a paste filler. If the wood is to be stained, the filler should be colored the appropriate tone. The staining is usually done before the wood is filled.
After the paste filler has been applied and become dry, a thin coat of shellac should be given to the whole surface in order to produce a smooth, non-porous surface. Shellac being expensive, a liquid filler is often substituted; and in this case care should be taken to select one of good quality, made with a pigment base and a good varnish, and thinned with turpentine. There is so much adulterated shellac on the mar ket to-day, cut with wood alcohol, that many finishers now prefer to start at once with the varnish coats instead of using a shellac or liquid filler surfacer. In any case where there is dan ger of moisture penetrating through the wood from behind, shellac should be avoided. Under no circumstances should oil be used as a primer.
After the work has been filled, all nail-holes, cracks, or other defects should be puttied up. This is a matter requiring the most careful judg went. All wood darkens in time; and if the putty is tinted to match the new woodwork, in the course of five or six months every nail-head and every crack will show out against the darker ground. It is best to make the putty three or four shades darker than the wood at the start.