Preparing a Wood Surface for Finishing
How to prepare wood surfaces for finishing and staining, instructions for surface preparation.
¶ Getting a surface ready for finishing is work which should be done with the utmost care when the finish is to be the finest possible and even for ordinary jobs. Unfortunately the price received for many jobs of finishing: is so low that it is quite impossible to do more than the most rapid cleaning and sandpapering, so that is where the responsibility must be placed for many muddy, cloudy natural and stained finishes.
¶ New Surfaces. Wood to be finished in natural or stained color is especially deserving of most thorough work in preparing it for the finishing process. It should first be dusted off with a duster brush or a broom in the case of floors. Then all spots of plaster, dirt or grease ought to be removed. Usually such spots will come off with a washing over with benzine, using a putty knife to scrape off as much as possible. If the wood is oak, walnut or other open-grain variety, be particular to remove dirt, lime and grease from the pores of the wood. When such spots are not properly cleaned, stain does not take hold and penetrate and the finish is thus spotty in appearance.
¶ New surfaces which are to be finished with paint and enamel ought to be cleaned well, but there is no need to be so particular about light stains. All loose particles on the surface should, however, be removed.
¶ New surfaces which show dark stains from rust or other substances should be bleached out in such spots before being finished in natural or stained colors. The wood bleaching methods will be found later.
¶ New surfaces after cleaning should next be sandpapered if the finish is to be natural or stain colors. This is not necessary for paint or enamel finishes. If water stain is to be used many finishers prefer to brush or sponge on a water coating before sandpapering. The water stain will raise the grain of the wood, making little wood fibres stick up all over. If the surface is wet in this way before staining, the water stain does not raise the grain so much and the second sandpapering is very light. If the water wetting is not done before staining with water stain the sandpapering operation on some woods must be done so heavily that some of the stain color will be cut off the wood. This sandpapering operation on new wood before or after wetting should be done with No. 1 and No. 00 paper, depending upon the roughness of the wood. Sometimes it is well to go over the wood first with a No. 1 paper and finish up with a finer grade.
¶ The cleaning necessary after sandpapering should be well done with a duster brvsh on ordinary jobs. On fine furniture and cabinets more effort should be spent to remove every particle of dust. In furniture factories the dust from sanding is blown out of the pores with compressed air.
¶ Woods to be finished in natural color as light as possible, maple, birch, etc., are often bleached before any finishing coats of filler, varnish or shellac are put on. The bleaching raises the grain of the wood and a thorough job of sandpapering must be done after that process. The bleaching methods will be found later.
¶ New surfaces to be finished in natural or stain colors and which show cracks and holes should be filled to remedy these defects. Plaster of Paris soaked in water is preferred by many finishers for this filling because it will absorb stain and also will take on the coloring given by filler. Other putty does not absorb color. On stained finishes as a rule the putty is put into the cracks and holes after the stain is dry. Putty mixing formulas will be found later in this chapter.
¶ After putty is dry it should be sandpapered down smooth and clean. Then the surface should be cleaned up around the repairs.
¶ Old Surfaces. Preparing an old painted surface for re-painting or for an enamel finish simply calls for sandpapering to remove dirt, grease and roughness, assuming that the old paint is firmly attached to the surface. If it shows any tendency to crack and scale or alligator it should be removed entirely from the surface with sandpaper or liquid paint remover.
¶ Old enamel surfaces which are to be refinished call for sandpapering just enough to cut the old gloss and clean up the surface. Defects such as holes, bruises and cracks should, of course, be filled with good lead and whiting putty.
¶ Old varnish to be refinished with varnish, paint or enamel should be rubbed down clean and smooth with No. 1 sandpaper just enough to remove the gloss, dirt and grease, assuming that the old varnish has not crazed or alligatored. If it shows indications of an infirm hold on the wood, better take off all of the varnish with liquid or paste varnish remover. After sandpapering to remove high gloss some finishers prefer to wash down a varnished surface with benzole or with warm water and sal soda to make it absolutely safe to paint or enamel. The soda bites into the varnish a little.
¶ Old varnished surfaces which are to be refinished with stain call for stripping off all of the varnish, using liquid or paste varnish remover. A thorough job must be done. If any of the varnish is allowed to remain on the surface, even in a very thin coat, it will prevent new stain from penetrating into the wood. A penetrating stain is then needed to do an even coloring of the wood. After stripping off the varnish a most thorough washing should be done to remove any wax left on the surface by the remover. Wash up with benzole, preferably. Benzine, naphtha or turpentine will also do this clean-up work.
¶ On low-priced work restaining is sometimes done without removing the old varnish. The old varnish is rubbed down with No. 1 sandpaper to remove the gloss and clean up any dirt or grease on it. Then it is washed down with benzole brushed on to cut the old varnish a little,or is washed down with hot water in which sal soda has been dissolved to do the cutting of the old varnish. The stain used for such work is spirit aniline stain which must be brushed on very deftly with as few strokes of the brush as possible to avoid raising or lifting the old varnish. Brush this stain only in one direction. For very cheap work a good brush hand can coat the surface with shellac to which a little pigment or aniline color has been added to make a stain. These processes simply color the wood and supply a gloss. They do not pretend to enhance the beauty of the wood. In this sort of work it is sometimes necessary to touch-up bare, worn-through spots with a coat of thin spirit stain before staining the whole surface, this to make the worn places match the whole surface in color.
¶ Old stained or natural varnished surfaces from which the old finish has been stripped off with varnish remover are often too dark in color to produce a nice finish with the new stain. Then it is necessary to bleach out the old color before restaining. The bleaching methods are presented later.
Next Page: Wood Putty, Putty Mixing.
This is Preparing a Wood Surface for Finishing.
www.craftsman-style.info is Copyright © 2005-12 by International Styles