PKESERVATION OF SPECIMENS IN PLASTICS 15 



sisting of a single sheet of newsprint or other suitable thin paper, and 

 these folders should be sandwiched between the corrugated ventilators, 

 with or without blotters, as the case may require. 



Specimens should be laid out in the pressing folders as naturally as 

 possible by using a wooden splint or preferably a fairly stiff feather or 

 small brush. Only as much material should be laid out in each folder 

 as can be kept properly in position while closing it and placing it in the 

 press. The upper sheet of the folder should be let down carefully to 

 permit making final rearrangements as the specimen is covered by it. 

 Pads of absorbent cotton or cellulose fiber held between sheets of thin 

 paper or gauze may be used in place of the pressing folder, or in addition 

 to it. Such pads are helpful in equalizing the pressure on parts of speci- 

 mens of uneven thickness. The press should be closed with care to 

 avoid shifting the ventilators, and the straps should be drawn up alter- 

 nately by moderate stages until they exert the fullest pressure obtain- 

 able. Further tightening of the straps is usually necessary after a few 

 hours of drying, and in the case of succulent or buDsy specimens this 

 may have to be repeated several times. 



Drying with heat to retain the natural color. — As soon as the press has 

 been closed, it should be placed over a suitable source of heat in such a 

 position that the heated air will rise through the corrugations and carry 

 away the liberated moisture as rapidly as possible. By maintaining a 

 temperature of 45° to 55° C. (113° to 131° F.) it will be found that most 

 specimen material can be suitably dried with good color retention in 24 

 hours or even less time. Still more rapid drying and even better color 

 retention may sometimes be obtained when an electric fan is used to 

 force heated air through the press. 



Storing pressed specimens. — If the dried specimens are not to be used 

 at once, it is advisable to transfer them to a storage press which should 

 be kept in a drying case supplied with a desiccant. If this is not done, 

 the colors which have been temporarily retained during pressing and 

 drying will tend to fade in a short time when moisture is reabsorbed 

 from the air. 



Care must be used in handling thoroughly dried specimens because 

 of their extreme brittleness. In the case of dried specimens that are to 

 be treated with preserving fluid it is usually advisable to rehumidif} r 

 them partially by subjecting them to moderately moist air for an hour 

 or two before laying them out for processing. If the air in the room is 

 not sufficiently humid to soften them quickly, they may be placed in a 

 moist chamber or covered for a few minutes with damp newspapers. 



Laying out the specimen and applying the preserving fluid. — A sheet 

 of transparent Vinylite plastic, 0.030 inch in thickness and large enough 

 to leave a free space of at least 1 inch all around the specimen, should be 

 employed as the base of the permanent mounting plate. This sheet 

 should have its back protected with plain paper or tissue, and then be 

 laid on a piece of waxed paper large enough to provide a margin of 

 approximately 2 inches on all four sides. A temporary cover sheet of 

 0.0015-inch flexible grade cellulose acetate film is also required, and 

 this should be cut to such a size that it will extend one-half inch beyond 

 the edges of the Vinylite mounting sheet when placed on it. 



In laying out the pressed specimen, a moderate amount of preserving 

 fluid is 'first applied on the mounting sheet and then spread over the 



