Shellac Mixing, How to Make Shellac
A description and formula for how to make shellac varnish and finish.
4 ½ pounds pure gum shellac, 1 gallon denatured alcohol. Makes 1 ½ gallons of varnish.
Dissolve the gum by placing in a glass or earthen jar or jug which can be corked tightly with the alcohol. Shake up the contents occasionally until all the gum is dissolved. By placing the container in a pail of boiling hot water the gum will be dissolved quicker. If the shellac flakes are put into a bag and pounded to powder the gum will dissolve more quickly. Small quantities may be dissolved in glass fruit jars, using the rubber; screw down the cover tightly. Store the shellac, especially white or bleached, in dark places. Light darkens the color. Storage in tin for any length of time will also make the shellac darker. This proportion of gum and alcohol makes a varnish which is too thick for most surfaces. A little more alcohol should be added when about to spread the shellac. There are very few places where thick shellac is advisable. It does not make a secure foundation for subsequent coats of varnish, paint or enamel.
¶ The liquid shellac commonly sold is what is called a 4-pound cut, meaning that 4 pounds of shellac dry gum have been dissolved in 1 gallon of alcohol. This is a fairly heavy brushing consistency and is thinned more for most purposes with alcohol. It is also possible to purchase 4 ½ and 5-pound cuts. A 3 ½ pound cut is correct for general use.
¶ For mixing large batches of shellac what is called a U. S. Government Formula may be used. It reads:
Orange Shellac, dry scales, 31 pounds.
Makes 100 pounds of shellac varnish, or about 13 1/3 gallons of 7 ½ pounds per gallon.
¶ Pure shellac gum commands a fairly high price and so there has always been some call for cheaper material. Those who cater to this class of trade necessarily must extend the pure shellac gum to meet the price and so liberal quantities of cheap rosin, manila gum or other substances are mixed with it. This cheapens the quality as well as the price and those who use such materials are apt to run into considerable trouble. The mixtures of pure shellac are the safest to use, far safer than some of the liquid fillers of cheap character which do not bring out the true beauty of the wood grain and are apt to cloud the finish, if indeed, they do not cause the varnish coats to crack and craze. Doped shellac will also gum up the sandpaper and prevent cutting down a coating to a level, smooth surface. Pure shellac will dry hard enough to sandpaper smoothly and cut off clean in thirty minutes, but adulterated shellac mixtures may remain tacky for hours and never dry real hard.
Next Page: Applying Shellac Varnish.
This is Shellac Mixing, How to Make Shellac.
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