CH. VIII] PREPARATION OF LANTERN SLIDES 205 



diagram or table, etc., and then have a photographic lantern slide 

 made. 



In preparing these slides direct, a device of the artists of earlier 

 times who painted lantern slides, is used. That is, the slide is 

 cleaned carefully and then coated with a thin solution of some hard 

 varnish or with gelatin (fig. 112, 317). After the varnish has 

 thoroughly dried one can use a pen or a brush upon the varnished 

 surface with the same facility as upon paper. The hand-made slide 

 is then mounted as usual and can, of course, be used indefinitely. 



If they are for a special occasion as in projecting election 

 returns, games, etc., the slides are used without a cover-glass. 

 They may be easily cleaned off with turpentine or xylene and used 

 over and over. 



317. Coating the lantern-slide glass with varnish. One of 



the best varnishes for this purpose is composed of 5% dry Canada 

 balsam or gum dammar in xylene or in turpentine; or 10% natural 

 Canada balsam in xylene or toluene. Or one can take some good, 

 varnish, especially Valspar, one part and xylene, toluene, gasoline 

 or turpentine nine parts. All of these thin solutions should be 

 allowed to stand until they are clear, and only the clear part used. 

 If one is in haste it is possible to filter the thin varnish through filter 

 paper. 



For coating the glass, the best way is to hold the clean glass flat 

 by grasping the edges with the thumb and fingers. Then varnish 

 is poured on, and the glass tilted slightly until the whole surface 

 is covered. The excess is poured off one corner back into the 

 bottle. Then the glass is stood on edge to dry. In a warm dry 

 room 15-20 minutes will suffice for varnish in xylene or toluene. 

 If turpentine is used it may require half a day or more. When the 

 varnish is once dry the glass can be used at any time. 



As it is not easy to tell which side has been varnished, a slight 

 mark in one corner of the varnished surface with a glass pencil or 

 pen will enable one to tell quickly and with certainty. 



318. Coating the lantern-slide glass with 10% gelatin. For 



this, some clear gelatin is made into a 10% solution in hot water, 



