16 



MISC. PUBLICATION 679, U. S. DEPT. OF AGRICULTURE 



greater part of the area the specimen will occupy. The specimen, 

 which has been preferably softened by partial moistening, is then placed 

 in position and a small additional amount of preserving fluid applied 

 over its upper surface (fig. 2). 



The cover film is next lowered into place in register with the Vinylite 

 mounting sheet so that the one-half-inch overlap is maintained all 

 around. While this is being done, the specimen should be held in posi- 

 tion, or rearranged as needed, by using a wooden splint under the film 

 and by working on it with the fingers above the film. When the cover 

 film has been placed properly in position, the waxed paper extending 

 beyond its edges should be folded in over it so as to provide a marginal 



Figure 2. — Specimen material that has been pressed and dried before treatment can 

 be laid out on plastic sheets and treated with the preserving fluid. 



pocket all around for receiving the excess preserving fluid that is later 

 to be extruded from the layout. 



Preliminary working over. — The layout should now be worked over 

 by applying light pressure with the fingers so as to spread the preserving 

 fluid out from the specimen and surround it with a sealed area at least 

 1 inch wide. This will serve to prevent re-entrance of air when the 

 original bubbles are eliminated. The larger bubbles should then be 

 forced out by displacing them with fluid which is pushed back toward 

 the specimen for the purpose. Finally a moderate amount of fluid 

 should be left in contact with the specimen to provide the necessary 

 preserving action. It is often advisable to allow the layout to stand for 

 an hour or two in this condition before setting it aside to cure, because 

 additional bubbles may form which require elimination. 



When the specimen has been worked over as much as needed, the 

 excess fluid around it should be removed by extruding it by means of a 

 plastic squeegee (fig. 3, A) or a firm rubber roller (fig. 3, B) applied 

 through a free work sheet of rigid type 0.002-inch cellulose acetate film 

 laid over the layout to protect the cover film from being torn or punc- 

 tured by the extra pressure. The squeegee, or roller, should not be 



