xii. a, b Aguilar: Linseed and Lumbang Oils 239 



The most satisfactory results, however, were obtained by paint- 

 ing over paper of fair quality, sized with some inert substance 

 from which paint could readily be removed by soaking in warm 

 water. Among the substances tried were library paste, agar- 

 agar, sugar sirup, and glue. Of these, the use of paste or agar 

 resulted in a shriveled film of low tensile strength. The use 

 of sugar sirup 9 was satisfactory, but since the glue method, as 

 described by Gardner, ,n was simpler and gave more uniform 

 results, the latter was adopted for this work. The method of 

 procedure was as follows: The paint was applied to the sized 

 paper and allowed to dry. It was then removed by immersion 

 in water at 40° C., washed off with fresh water to remove the 

 glue, hung on a glass rod to dry, and placed in a suitable con- 

 tainer to prevent the accumulation of dust and insects. 



Tensile strength and elasticity. — In testing the paint films, a 

 modified Gardner-de Horvath n film-testing machine was em- 

 ployed. The apparatus is shown on Plate I. 



The pressure was measured by means of a mercury manom- 

 eter. This was made self-registering by placing inside the 

 manometer tube an indicator, which remained at the highest 

 point reached by the mercury column. The stretch was recorded 

 by means of an aluminium rod resting on the center of the film. 

 This rod was in turn fastened to the short arm of a lever and so 

 delicately counterpoised that it exerted no appreciable pressure, 

 yet rose and fell with any movement of the film. As the long, 

 or pointer, arm of the lever was ten times as long as the short 

 arm, it is obvious that any movement of the film was transmitted 

 tenfold to the pointer arm and could thus be estimated with 

 a certain degree of accuracy. 



To study the behavior of oil films, 12 precipitated silica passing 

 through a 200-mesh sieve was incorporated with the oil in the 

 proportion of 15 per cent silica by weight. The films were made 

 of three coats of 2.5 grams of paint each, applied to 400 square 

 centimeters of sized paper. 



Table III shows the effect of age upon the strength of films 

 made from mixtures of linseed oil with lumbang bato oil in 

 different proportions. 



9 Labordere, P., and Anstett, F., Chem Eng. (1913), 17, 1. 



10 Op. cit., p. 71. 



11 Gardner, op. cit., p. 79. 



12 Gardner, op. cit., p. 31. 



