To obtain the finish known as egg-shell gloss, (1) Coat the smooth wood with from three to six applications of thin shellac. Allow each coat twenty-four hours in which to harden. (2) Rub to a smooth surface each hardened coat using curled hair or fine steel wool or fine oiled sandpaper.
157. Oil or Copal Varnishes.
—Oil varnish is composed of copal gum, boiled oil and turpentine. Copal gums are obtained from Africa mainly, in certain parts of which they are found as fossil resins, the remains of forests which once covered the ground.
Pressed flaxseed furnish crude linseed oil while the long leaf pine of the South, furnishes the turpentine pitch.
The oil is prepared for use by boiling it in huge kettles with different materials which cause it to change chemically. It is then put away to settle and age, that is to clear and purify itself. It takes from one to six months for the oil to reach a proper degree of clearness and purity. Turpentine is obtained from its pitch by distillation.
The copal gums are melted and boiled thoroly with the oil. Turpentine is added after the mixture of gum and oil has cooled sufficiently. The whole is then strained several times, placed in tanks to age or ripen. From one month to a year, or even more, is required.
The quality of varnish depends upon the qualities of the gums, the proportion of oil and turpentine and the care which is exercised in the boiling process.
158. Flowing Copal Varnish.
—(1) Lay on the varnish quickly in a good heavy coat. Use a good varnish brush and dip the bristles deeply into the liquid, wiping them off just enough to prevent dripping. (2) Wipe the bristles quite free of varnish; go over the surface and pick up as much of the surplus liquid as the brush will hold. Replace the varnish in the can by wiping the bristles on the wire of the can. Repeat until the entire surface has been left with but a thin smooth coating.
Two, three, four or more coats are applied in this manner, forty-eight hours being allowed between each for drying. Dry varnish comes off in sanding as a white powder; if not dry it will come off on the sandpaper as little black spots.