RESINS. 
25 
transparent, some opaque, most only translucent. Most give 
a white streak, are brittle and easily powdered, and com¬ 
monly have a characteristic smell or taste. 
The melting points of resins vary from 75°-360° C., and 
are characteristic for the various kinds. Their solubility 
varies much with regard to the different solvents, some 
dissolving easily, others with difficulty, in alcohol, ether, 
carbon, disulphide, oil of turpentine, eajuput oil, benzol, 
&c. 
The chemistry of resins is complex, and does not require 
discussion in this work ; reference may be made to Wiesner’s. 
Rohstoffe, and to works on chemistry. They are divided 
into two main groups, those which, like benzoin, storax, &c., 
contain esters of aromatic acids, and those which, like san- 
darach, copal, dammar, &c., contain only resinic acids. 
The chief use of resins in the arts is in the manufacture 
of varnish, which consists of a solution of resin in oil of 
turpentine, alcohol, or other solvents. When brushed over 
the surface of wood or other object to be preserved, the 
solvent evaporates, leaving a thin coating of the resin. The 
manufacture of varnishes is dangerous, on account of the heat¬ 
ing required, and the great inflammability of the substances 
employed. They may be roughly classified into oil and 
spirit varnishes ; the former include the. ordinary carriage 
and copal varnishes, made by melting the resin, mixing with 
the required quantity of clarified linseed oil, afterwards 
boiling and mixing with the suitable amount of oil of 
turpentine. The latter are chiefly the fine varnishes used 
in photography and cabinet work, and are made by dis¬ 
solving the resin in spirit of at least 60 over proof, by the aid 
of gentle heat. Details of the processes of varnish-making can 
be found in such books as Spon’s Workshop Receipts, Ure’s 
Dictionary of Arts and Manufactures, &c. There is every 
reason to suppose that several very good varnishes might be 
locally made in Ceylon, from local resins, and thus replace 
E 
[May, 1902.] 
