24. PHILIPPINE RESINS, GUMS, AND OILS 
MANILA COPAL AS AN INGREDIENT OF VARNISHES. 
As previously stated, Manila copal is used principally as an 
ingredient of varnishes. Spirit varnishes are solutions of resin 
in a volatile solvent such as turpentine, benzene, alcohol or some 
other solvent. Plain oil varnishes consist of only linseed oil or 
some other drying oil. The oleoresinous varnishes contain all 
the ingredients of both spirit and plain oil varnishes, and have 
properties common to both. The manufacture of oleoresinous 
varnishes consists essentially in mixing resin, turpentine, and 
a drying oil, such as linseed oil, in the proper proportions. 
Usually resins do not dissolve readily in drying oils unless the 
mixture is heated somewhat, and even then the resin frequently 
separates upon cooling. It is therefore customary to heat both 
the oil and resin before and after mixing. Richmond showed 
that although Manila copal loses weight when heated, the melted 
resin differs from the raw resin only in the amount and nature 
of unsaponifiable matter, that is, in the free amorphous acids. 
He concluded that the resin which enters into varnish manufac- 
ture consists essentially of free acids of the same composition 
as the free acids in the original copal, and that there is no 
particular reason for heating the resin to a high temperature 
either before or after mixing. He found that oleic, palmitic, 
and linolic acids dissolve the resin acids of Manila copal at 
moderate temperature. 
A quantity of the mixed fatty acids of linseed oil was prepared and 
added in varying proportions to raw linseed oil, depending upon the 
quantity of unmelted resin it was desired to dissolve, and it was found 
that raw or boiled linseed oil, containing the free, mixed, fatty acids of 
linseed oil in the proportions of 10 to 30 per cent calculated as oleic acid, 
formed homogeneous solutions with raw or fused Manila copal when the 
latter is added in the proportion of 10 to 30 gallon varnishes and heated 
for a time at a maximum of 200°. When the turpentine was added before 
the oil, the boiling point of turpentine, 155° to 165°, was sufficiently high 
to effect complete solution with the exception of such foreign matter as 
may be present in the resin. The subsequent addition of turpentine to the 
oil and resin did not produce any cloudiness. 
Varnish prepared as described above was used for varnishing 
native hardwood. The varnish film remained a year without 
showing any appreciable loss of luster. 
Richmond concluded that: 
The changes which take place during the cooking of varnish are largely 
changes in the oil rather than the resin, i. e., it is possible so to treat 
linseed oil, either by boiling or by adding to it linseed-oil acids previous 
to its addition to the fused resin, that it will form a clear, homogeneous 
mixture with the latter which will remain so upon cooling, without sub- 
sequent heating to temperatures greater than 150° to 200°. 
