Wood turning Finishing Techniques




Introduction


One of the most difficult woodworking tasks for beginners is finishing. There is a bewildering array of finishing products available to woodworkers today but comparative product information is hard to come by. All finishes have certain strengths and weakness when compared to each other. An excellent reference on this subject is Understanding Wood Finishes by Bob Flexner and I highly recommend it.

This article is an attempt to provide you with a few easy finishing procedures to follow and to explain the differences between types of finishes. Instead of an all-encompassing review, these procedures are written expressly for woodworks with little experience at finishing. By following these simple steps, one should be able to achieve a very nice finish on almost any woodworking project.

General Advise

The first procedure of a good finish starts with surface preparation. Sand, scrape, or plane the surface until the surface is free of defects and uniform. The amount of sanding and the grit of sandpaper used can have a significant impact upon the way "stain" will appear on a wood surface. The wood surface should be evenly sanded to a 150 or 220 grit uniform surface. Take care to remove all glue marks and scratches, common stains will highlight these defects. If you have not done much staining you should experiment before applying any stain to your project.

When applying several coats of a film type finish, it is best to apply the gloss version of the product as a base even when a satin sheen is desired as the end product. The satin sheen products contain particles in them to defract light. Many layers of these defractors may make a finish look muddy compared to a finish built up with clearer products.

When sanding the finish between coats, sandpaper is used to remove any large irregularities and to make the finish level. Scotch pads or synthetic steel wool is used afterwards to more uniformly abrade the surface and obscure any scratches made by the sandpaper and to provide a better surface for the following finish layer. As the finish is built up into a more level surface, the grit number of the abrasives used between coats is increased.

It is not a necessity that you use the same finish technique or product on the entire project. For example, assume you chose Danish oil as the primary finish for a chest of drawers. You may use polyurethane or acrylic for the drawer boxes, interior parts, or the applied back. This would save a great deal of time and effort.

Do not apply any stains or finishes in direct sunlight.

If the finish has not dried thoroughly it will ball up or make "corns" on the sandpaper. If this is the case, allow the finish to dry more, continuing to sand and applying more finish on top may degrade the overall finish quality.

One technique I always use is to make a sample board out of cutoffs from the project. With this sample piece I can test different stains and finishes to see how the project will appear when complete. It is also used to test any finishing technique deviations before applying them to the project.

Be sure to read and follow the safety precautions listed on the product container.

Definition of terms:

Polyurethane Refers to oil based products only.

Sheen Surface reflection characteristic, either gloss, semi-gloss, or satin.

Smooth Surface texture, smooth does not mean gloss.

Water Based Refers to water based polyurethane and similar water based products
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