VARNISH AND PAINT EXPERIMENTS. 



37 



the preparation of the varnishes that the difference in odor between 

 gum turpentine and wood turpentine is most strongly brought out, 

 as it is much more pronounced at this stage than in the cold turpen- 

 tine or in the completed varnish at ordinary temperatures, though 

 here, too, it is quite easy to differentiate the several varnishes. The 

 odor of the hot varnish thinned with the steam-distilled turpentine 

 was much more objectionable to the writer than that of the varnishes 

 thinned with the destructively distilled samples. In the former case 

 the odor can be best described as resinous and nauseating, while in 

 the latter case it was resinous, penetrating, and smoky. 



The viscosity of the varnishes was determined by the Doolittle vis- 

 cosimeter and found to be as follows, when expressed in angular 

 degrees of retardation: 



Viscosity of three kinds of varnish (expressed in angular degrees). 



That is, the different samples of the same kind of varnish were not 

 at all alike in consistency. This fact has but little significance, how- 

 ever, except that it made it necessary for each workman to thin the 

 varnishes himself before using them. It is more than probable that 

 this would have been done in any case and the final results do not 

 indicate that the differences in consistency had any practical effect 

 on the finished coat. It will be seen from the following table, and 

 from Table 11, page 69, that the experimenters seldom thinned the 

 varnishes in conformity with their determined viscosity. Neither is 

 there any apparent connection between the turpentine content, the 

 thinning required, and the time of drying of the different varnishes. 



Order in which the varnishes should be thinned. 



