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Saturday, June 03, 2006

PREPARATION OF OLD SURFACES

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.

 

Old Surfaces

Preparing an old painted surface for repainting 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 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 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 soda has been dissolved to do the cutting of the old varnish. The stain used for such work is an oil 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 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 oil stain before staining the whole surface, this is 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 in this chapter.

 

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This tip, and many more, can be found in the 130+ page eBook at this site: http://www.charliehasit.com/woodfinishing

 

 

 

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