2933. Bookbinders' and Colorless Varnish

2933.      Bookbinders' and Colorless Varnish. Mr. A. Schmidt gives the following directions for making these and several other beautiful varnishes: For 1 pound good shellac take 4 ounces crystallized carbonate of soda, and 11/2 gallons water; put the whole in a clean iron or copper vessel of double the capacity, and, under constant stirring, bring it to boiling over a slow fire. The shellac will dissolve, and, if it is intended to make colorless French varnish (see No. 2935 (French Transparent Colorless Varnish)), the solution has to be run through a woolen cloth. For brown bookbinders' varnish, or a colorless varnish for maps, photographs, etc., the solution has to boil for about an hour longer, but only simmering, and then to cool very slowly without stirring; better let it stand over night, and let the fire go out under it. In the morning a wax-like substance will be found on the surface of the solution, and the other impurities of the shellac as a deposit on the bottom of the vessel. The solution is likewise to be run through a woolen cloth and then to be filtered. (See No. 2934 (Filter for Shellac).) To make a transparent brown varnish - bookbinders' varnish - this filtered solution has to be precipitated with diluted sulphuric acid (1 part acid to 20 parts water), the precipitate collected on a coarse muslin cloth, and washed out with cold clear water till it runs through without taste. (See No. 24 (Precipitation).) Then fill a stone or wooden vessel with boiling water, and throw the precipitate in it; it will directly soften and stick together; this half mass has to be kneaded in the hands, doubled up, melted, and drawn out till it assumes a fine silky lustre, then drawn out to the desired thickness in sticks, like candy, and it is then ready for solution. To make the Bookbinders' Varnish, dissolve 1 part of the precipitate in 2i parts 95 per cent, alcohol. To make the Colorless Varnish, dissolve 1 part of the precipitate in the same quantity of alcohol. Add 11/2 drachms oil of lavender to each pint. The colorless varnish will look like whey, but more transparent.

2934. Filter for Shellac

2934.    Filter for Shellac. To make a filter for shellac-, take a small wooden keg, remove the top and bottom, and fasten to one side a piece of muslin; on the muslin bring about 4 inches fine, washed sand, and on top of the sand a layer of clean straw; then pour the solution into the filter and let it run through. Should the first portion run through be not perfectly clear, like red French wine, it has to be brought back to the filter. When nothing more will run through, pour some clean water on the filter to wash the remaining solution out.

2935. French Transparent Colorless Varnish

2935.    French Transparent Colorless Varnish. To make white French transparent colorless varnish for maps, the solution (see No. 2933 (Bookbinders' and Colorless Varnish)) has to bo bleached. The bleaching fluid is made as follows, and the proportions are for 1 pound of shellac: Take 1 pound good English chloride of lime, dissolve it in 14 pounds cold water, triturating the lumps well; let it subside, and decant the clear fluid; add 7 pounds of water to the residue, and, when subsided, add the clear liquor to the other; precipitate this liquor with a solution of carbonate of soda, let the carbonate of lime settle, and decant the clear chloride of soda; wash the sediment out with water, and add the clear liquid to the former, put it in a high stone jar, and give it a rotary motion with a wooden stick, pouring in at the same time very diluted sulphuric acid, till it assumes a greenish color and a smell of chlorine is perceptible. Then add some of this liquid to the solution to be bleached, under constant stirring, till all the color is gone. French polish will look like milk. Then precipitate with dilute sulphuric acid, exactly as the solution for bookbinders' varnish, and treat the precipitate in the same manner, in hot water. (See No. 2933.) All iron must be carefully avoided as soon as the chlorine liquor is added. Dissolve 1 pint of the above in 3 pints of 95 per cent, alcohol, and do not add any oil of lavender, as in No. 2933. For photographs this solution is too strong; 1 part of bleached shellac to 6 parts alcohol will answer. For maps the solution should not be applied immediately to the paper, but the latter should first receive a coat of boiled and strained starch.