ONE HUNDRED THOUSAND FACTS FOR THE PEOPLE. 



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439* 



to be as durable as any other solution of 

 copal. 



Copal may also be dissolved in spirits 

 of turpentine by the assistance of 

 camphor. 



Turpentine varnishes dry more slowly 

 than those made with alcohol, and are 

 less hard ; but they are not so liable to 

 crack. 



VARNISH, Copal.— a. Oil of turpen- 

 tine one pint, set the bottle in a water 

 bath and add in small portions at a time 

 three ounces of powdered copal that has 

 been previously melted by a gentle heat 

 and dropped into water; in a few days 

 decant the clear. Dries slowly, but is 

 very pale and durable. Used for pic- 

 tures, etc . 



b. Pale hard copal two pounds; fuse, 

 add hot drying oil one pint, boil as be- 

 fore directed, and thin with oil of turpen- 

 tine, three pints, or as much as sufficient. 

 Very pale. Dries hard in twelve to 

 twenty-four hours. 



c. Clearest and palest African copal 

 eight pounds; fuse, add hot and pale dry- 

 ing oil two gallons, boil till it strings 

 strongly, cool a little, and thin with hot 

 rectified oil of turpentine, three gallons, 

 and immediately strain into the store can. 

 Very fine. Both the above are used for 

 pictures. 



d. Coarsely powdered copal and glass, 

 of each four ounces; alcohol of ninety 

 per cent., one pint; camphor, one-half 

 ounce; heat it in a water bath so that the 

 bubbles may be counted as they rise, ob- 

 serving frequently to stir the mixture; 

 when cold, decant the clear. Used for 

 pictures. 



e. Copal melted and dropped into 

 water, three ounces; gum sandarach, six 

 ounces; mastic and Chio turpentine, of 

 each two and one-half ounces ; powdered 

 glass, four ounces; alcohol of eighty-five 

 per cent, one quart ; dissolve by a gentle 

 heat. Used for metal, chairs, etc. 



All copal varnishes are hard and durable, 

 though less so than those made of amber, 

 but they have the advantage over the 

 latter of being paler. They are applied 

 on coaches, pictures, polished metal, 

 wood, and other objects requiring good 

 durable varnish. 



/ Hard copal, three hundred parts; 

 drying linseed or nut oil, from one hun- 

 dred and twenty-five to two hundred 



and fifty parts; oil of turpentine, five 

 hundred parts; these three substances are 

 to be put in three separate vessels; the 

 copal is to be fused by a somewhat sud- 

 den application of heat; the drying oil is- 

 to be heated to a temperature a little un- 

 der ebullition and is to be added by small 

 portions at a time to the melted copal. 

 When the combination is made and the 

 heat a little abated, the essence of tur- 

 pentine, likewise previously heated, is to 

 be intioduced by degrees; some of the 

 volatile oil will be dissipated at first, but 

 more being added, the union will take - 

 place. Great care must be taken to pre- 

 vent the turpentine vapor from catching 

 fire, which might occasion serious acci- 

 dent to the operator. When the varnish 

 is made and cooled down to about 130^ 

 of Fahrenheit, it may be strained through 

 a filter, to separate the impurities and un- 

 dissolved copal. Almost all varnish 

 makers think it indispensable to combine 

 the drying oil with the copal before 

 adding the oil of turpentine, but in this 

 they are mistaken. Boiling oil of turpen- 

 tine combines very readily with fused 

 copal; and, in some cases, it will prob- 

 able be preferable to commence the 

 operation with it, adding it in successive 

 small quantities. Indeed, the whitest, 

 copal varnish can be made only in this- 

 way; for if the drying oil has been? 

 heated to nearly its boiling point it be- 

 comes colored and darkens the varnish,, 



This varnish improves in clearness by 

 keeping. Its consistence may be varied 

 by varying the proportion of the in- 

 gredients within moderate limits. Good 

 varnish, applied in summer, should be- 

 come so dry in twenty-four hours that 

 the dust would not stick to it or re- 

 ceive an impression from the fingers. To- 

 render it sufficiently dry and hard for 

 polishing, it must be subjected for several 

 days to the heat of a stove. 



g. Melt in an iron pan at a slow heat 

 copal gum powdered, eight parts, and add 

 balsam copavia, previously warmed, two* 

 parts. Then remove from the fire and 

 add spirits of turpentine, also warmed be- 

 forehand, ten parts, to give the necessary 

 consistence. 



h. Prepared gum copal, ten parts; 

 gum mastic two parts, finely powdered, 

 are mixed with white turpentine and 

 boiled linseed oil, of each one part, at a. 



