122 Laboratory Arts 



treated, can be regarded neither as satisfactory nor permanent 

 many kinds indeed will not withstand ordinary washing. 



On the whole, a well-gummed, unvarnished label is to be pre- 

 ferred ; the more so, as if printed varnished labels are used it is 

 practically impossible to secure uniformity owing to the neces- 

 sity of supplementing with MS. labels. At the same time some 

 preservative is necessary, and two fairly successful methods 

 of dealing with this are in use. 



1. Sizing and Varnishing. The labels are gummed, 

 applied, and allowed to dry; then brushed over with a weak 

 solution of gelatine and allowed to dry again. A thin coating 

 of transparent paper varnish is then applied, overlapping the 

 label by about |" all round, the result being a clean and bright 

 label, impervious to the attack of water, acids and alkalies, but 

 giving way tinder the action of alcohol, benzene, turpentine, 

 and similar liquids. Such a label has the disadvantage that 

 the varnish is liable to crack or chip if too thick or if subjected 

 to rough handling, and the process necessitates the withdrawal 

 of the bottle from service for two or three days. 



2. Waxing. This process is much more simple and con- 

 venient than that given above a bottle may have an old label 

 removed, a new one affixed and protected, and be returned to 

 service in a couple of minutes. Having gummed the label, one 

 end is fixed to the bottle and the other end left free, the label 

 being gradually pressed from the fixed end until completely 

 attached, in order to squeeze out all air bubbles. This is most 

 important. 



A quantity of pure white paraffin wax is then melted in a 

 porcelain dish and heated until it begins to smoke. At this 

 stage a flat brush is immersed, and, in a few moments, is stroked 

 rapidly across the label, commencing about | " over the edge, 

 and finishing the same distance over the opposite edge. If the 

 appearance be streaky, the wax is not hot enough, while if the 

 label become transparent, it is too hot. There is only about 

 10 C. difference between these two temperatures, and the cor- 

 rect temperature is best found by experience, as it appears 

 to vary with different operators. Practice will enable a label 

 to be accurately and neatly covered in two or three strokes 



