26 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 drjang 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 varnisTiing 

 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°. 



