248 CEMENTS, VARNISHES, AND CELLS. 



Cement cells must be built up one coat at a time. If the 

 second coat is added before the first is perfectly hard, the cell will 

 eventually break down. 



The best cell that I have found for dry mounts is made by 

 punching a hole in a piece of blotting paper of the proper size 

 and thickness. This is cemented to the slide with mucilage. A 

 paper "front" must be used, for, if a varnish is used, it will defeat 

 the object of the paper cell. If sweating should occur in one of 

 these cells, which only happens in exceptional cases, it is only 

 necessary to lay the slide on the warm table and apply a gentle 

 heat. As soon as the blotter is dried out it will absorb all the 

 moisture that may be in the cell. 



For balsam mounts I use brass curtain rings, cemented to the 

 slide with gold size, and well varnished on the inside with the 

 same. 



For dry mounts which are not liable to give off moisture, I 

 employ wax cells. They are quickly made and are very strong. 

 My method is as follows : A piece of single-thick sheet-wax, such 

 as is employed in making artificial flowers, is put on the centre of 

 a slide and held there by pressing the ball of the thumb against it. 

 The heat of the hand is just sufficient to make it adhere. When 

 the first piece is firmly attached, which can be told by the 

 absence of air bubbles when viewed from below, a second piece 

 can be added and secured in the same manner. In this w^ay cells 

 of any depth can be made. When the wax is of the required 

 thickness the slide is placed on the turn-table and with a sharp 

 scalpel a cell is " turned "out of the mass, as a turner fashions 

 a bowl in his lathe. A damp cloth on the end of the finger or a 

 small stick is used to clean the glass inside the cell. The wax 

 must be well varnished, or the volatile portions will escape and 

 collect in fine beads on the under surface of the cover. Wax 

 cells made in this way seldom become loosened from the slide, 

 even when roughly handled. 



Glycerine mounts I put up in glass cells. As these should be 

 attached to the slide with the solid marine glue, it is better to get 

 them ready prepared. I secure the covers with shellac, as it is 

 less liable to run in than white zinc. These mounts afterward 

 receive a coat of white zinc as a safeguard. 



