Skip to content

Wood Finishing: filling holes, sanding, sealing, staining, comparison of finishes

November 2, 2014

WOOD FINISHING

 

Steps: 1. Fill holes with wood filler

  1. Sand
  2. Seal
  3. Stain
  4. Comparison of finishes: Enamel, Wax, Oil, Lacquer, Shellac, Varnish

 

  1. MAKING WOOD REPAIRS

Examine surface in low-angle light. Look for scratches, chips, gouges, nail holes, open joints, grain tear out.

Dents can be steamed out: cover with a damp towel, hold a hot iron on the towel till it begins to dry out. Remoisten towel and repeat several times.

Bigger than dents: test the patch material on a scrap wood from your project. Adjust color to match. Use wood dough, wood putty or plastic wood to patch. These come in shades but you should save sawdust from your sanding in order to color the putty. Plastic wood absorbs very little stain and comes in a wide variety of tones. Apply w/ putty knife. Use up to two or three thin applications. Leave the last one a little higher than surface of wood. Sand it down after drying.

 

  1. FINISH SANDING

Use progressively finer grits of sandpaper each time you sand. Sand only with the grain. On end grain sand in just one direction to avoid rounding edges. Wipe wood w/ damp cloth (water) in between grit changes. If you are using a non-water based stain or finish you won’t need to raise the grain unless the piece has a penetrating finish and will live in a moist environment. End the sanding steps by wiping surface w/ damp sponge, letting wood dry then using 0000 steel wool to smooth the fibers down or sand them down. Repeat this last process once or twice then seal or stain. If using oil based seal or stain, do the final wipe down w/ cloth dipped and wrung out in mineral spirits.

 

  1. SEALING

Wood finishes must be compatible with the finish you’ve chosen or the successive layers won’t bond together properly. For instance, compatible layers might all be dissolvable in a common thinner be it water or oil thinners (such as turpentine, linseed oil or mineral spirits).

 

‘SEALER’ = any product capable of sealing wood surfaces. Typically used just before applying top coat, a sealer can also be useful before you stain.

 

SEALING

Sealer forms a solid bond between the wood and top coat.

Seal end grain before applying stain coz they are thirsty.

 

  1. STAINING

When used on light colored wood, stain gives color and character. It can also highlight grain figure.

Stain pigments: finely ground particles of color in suspension in oil or solvent, like a thin but opaque paint. It coats wood fibers and tends to conceal the grain.

Wood dyes: most are aniline, a coal tar derivative, dissolved in a number of mediums. The dye is absorbed by the wood fibers, allowing grain to show through.

 

Summary of above products: “one=step” products exist! These are stain/filler combinations, pigmented sealers, and all-in-one stain finishes. Many work well.

 

Pigmented oil stains: ready-mixed; sold as oil stain, wood stain, pigmented wiping stain. Not compatible with shellac or lacquer and shouldn’t be used on unfilled open grain woods such as walnut or oak coz their heavy pigments cloud the finish. Brush or wipe stain into the wood. Use small, circular motions if wiping. Brushing: in one direction. Either way, excess should be wiped off immediately using clean cloth. Wait 12-24 hours before sealing. Stir well before and during use.

 

Penetrating oil stains: Actually dyes carried by oil/resin medium; known as Danish oil or colored penetrating oil. Provide color and finish in one coat; wood grain shows through nicely. Apply w/ a clean rag, use same rag to remove excess oil and equalize surface color. Wipe stain while still wet; last strokes should be parallel to the grain.

 

Water base aniline dyes: powdered, mixed w/ hot water. Clear, permanent, brilliant color. Swells the wood so grain must be raised first or sand after staining. 24 hr. drying. Good for woods that need slight boost in color. Dries lighter than in solution.

 

Alcohol-base aniline dyes: not very light-fast. Spray to apply to avoid lap marks

Non-grain-raising stains: combines best qualities of water and alcohol-base stains w/ none of the disadvantages. Not light-fast, won’t raise grain. Quick drying, can be used under nearly any finish. Best if sprayed on, NGR stains not recommended for softwoods coz of uneven penetration.

Advertisements

Comments are closed.