How to Varnish
Tips on Varnishing
Varnish is used chiefly for outdoor finishing jobs, to preserve wood in a natural state using no other finish, to maintain a stain finish, and to preserve and refinish an old finish of stain, paint, or enamel.
Varnish finishes are easy to create. The wood, naturally, must be filled, then shellacked, then it is set for a light sandpapering for finishing. The usual varnish finish comprises of one or two coats of rubbing varnish followed by a coat of finishing materials.
There are several varnishes useful in finishing, both for cabinet work and for use in the home.
Begin with all your equipment at hand and in order:
clean varnish pots
closed brush keeper
sheets of 6/00 split-garnet finishing paper
For staining and shellacking, the surface should be properly set up for varnishing since varnish is basically transparent. Old wood can be washed using laundry soap or kitchen detergent, then sanded lightly with No. 00 paper. Take care not to take away portions of underlying color that fare to remain visible. When the original paint is cracked or peeled, remove it by sanding or by using chemicals.
Varnishing should be done in a dust-free room, well ventilated, at a temperature above 65 degrees Fahrenheit. Use just a varnish brush for varnishing.
For a good varnish job:
1. Set the surface carefully, filling up all holes, removing all blemishes and any undercoat that should not appear in the final finish. Varnish gives virtually no cover to blemishes.
2. Apply a coat of transparent natural-wood-filler paste thinned using turpentine to the consistency of milk. Brush with a strong movement with the grain until the gloss turns flat; next, before it is set, rub across the grain using a clean cloth. Avoid streaks and gathering of filler in the corners. Leave for 36 hours for drying.
3. Sand lightly using No. 00 sandpaper. Brush off the dust.
4. Put on a thin coat of white shellac mixed with 20 percent denatured alcohol. Brush with long, even strokes, with the grain, covering the whole surface. Allow no brush strokes to stay on. Keep in mind that shellac can't be retouched. Leave 3 hours for drying.
5. Sand lightly with No. 00 sandpaper. Brush off the dust.
6. Put on a thin coat of rubbing varnish. Brush with the grain, then across the grain with an empty brush, then with the grain, before replenishing the brush. Allow 36 hours for drying.
Hold the brush like a pencil at the ferrule, using a short, rapid, easy wrist movement, with almost no arm movement; hold the brush gently so that the brush upholds a chisel shape. The handle is held at a low angle leaning towards the direction of the stroke.
Work from the raw to the finished surface to prevent stroke marks. After 2 or 3 strokes, take out excess varnish against the strike wire on your paint can and tip out bubbles. Varnish is self-leveling and should need no re-brushing.
On vertical work, start at the upper right-hand portion (if you're right-handed) and work in 6-inch strip increments to the center. Then repeat from the left. Tip off every area as you finish. Check over each area from several angles to be sure the gloss is even.
When varnish in the can builds up a skin, the material must be strained through cheesecloth that has been dipped in weak shellac solution and dried out. Otherwise parts of the skin will blemish the varnish finish as debris.
7. Rub the surface using a mixture of pumice and water with the consistency of thin syrup. Rub this lightly with a felt pad with the grain. (don’t use a circular motion.) Wash the surface with a sponge and water, and dry using a cotton cloth or a chamois. Leave 24 hours for drying.
8. For a high finish, apply a second coat of rubbing varnish and do again the rubbing process.
9. Put on a coat of finishing varnish. Brush using long, even strokes with the grain, then, with the empty brush, across the grain and with the grain. Leave 72 hours for drying.
10. For a higher finish, use wax or oil polishing.
Be sure that the denatured alcohol you use is pure. Some kinds, like those used in radiators, have kerosene, which makes shellac gummy.