M. TECHNOLOGY. 533 



of Venice turpentine, covered with 24 ounces of alcohol, of a 

 specific gravity of 0.S33, are heated in a suitable vessel, with 

 continued stirring, over a slow fire or spirit-lamp, near but 

 not quite up to the boiling point, and the solution is com- 

 pleted by retaining the mixture at this temperature for an 

 hour, with frequent stirring. The varnish can be employed 

 immediately after cooling for mixing the paint. The Venice 

 turpentine prevents too rapid drying of the paint, and con- 

 sequent difficulty in spreading it. A weaker alcohol will 

 not only dissolve sandarac with difficulty, but is also liable 

 to become so dilute, by evaporation, as to cause a powdery 

 precipitate of the gum, and prevent the formation of an ad- 

 herent film. The white-lead to be used with this varnish is 

 first finely ground with water, and dried, and then again 

 ground with a muller with barely as much turpentine as the 

 operation requires. The varnish will not answer for this 

 operation, because it dries too rapidly, but the mass thus 

 obtained is stirred with as much varnish as is necessary to 

 form a paint that will spread readily ; about one pound of 

 white-lead being required to half a pound of varnish. As it 

 dries quickly it must be applied rapidly, and without pass- 

 ing the brush over partially dry portions. In course of half 

 an hour a second coat may be laid on. One peculiarity of 

 this paint deserving of notice is that it thickens so much in 

 the vessel from which it is used that it will not spread well, 

 a difficulty that may be remedied by thinning it, not with 

 alcohol, however, as might be supposed, but with a little of 

 the varnish, since the thickening is not due to the evapora- 

 tion of alcohol, but to a peculiar chemical action of white- 

 lead upon the sandarac. If the color is wanting in lustre 

 when dry, too much varnish has been employed, but a fine, 

 agreeable polish may be imparted to it, when perfectly dry, 

 by rubbing with a woolen rag. Paints with oil of turpen- 

 tine are just as easily prepared, but the choice of resins is 

 far more restricted, and the proportions are different from 

 those with alcohol. Dammar is found to answer every req- 

 uisite of hardness, cheapness, and freedom from color. Eight 

 ounces of the crushed gum are heated with 16 ounces of oil 

 of turpentine to 167 to 190, and kept at that temperature, 

 under continued stirring, about an hour, until solution is 

 complete. The varnish is decanted on cooling, and pre- 



