PRESERVATION OF SPECIMENS IN PLASTICS 19 



cover sheet consisting of 0.0015-inch thick flexible type cellulose acetate 

 film should be cut to a size that will leave an overlap of approximately 

 one-half inch bej^ond the edges of the Vinylite mounting sheet. 



Before laying out the specimen, a moderate amount of preserving 

 fluid of the proper type, as previously determined, is applied to the 

 mounting sheet and spread over the area to be occupied by the speci- 

 men. The specimen, which in this case is in a fresh condition, is then 

 placed in position, and a small additional amount of fluid applied over 

 its upper surface. The cover film is next put on in register with the 

 mounting sheet so that it overlaps the required half inch on all sides. 

 The specimen should be kept in its desired position while the cover film 

 is being applied by working under the film with a wooden splint and 

 above it with the fingers. Extreme care is necessary, especially if the 

 tissues are delicate, to guard against tears or bruises which would mar 

 the finished specimen, and pressure should ordinarily not be applied 

 directly upon any but the hard parts of the specimen until the tissues 

 have become toughened through prolonged curing. 



The waxed paper is folded over to form pockets for receiving the 

 extruded preserving fluid as explained in procedure A, and the preserv- 

 ing fluid should then be distributed around the specimen by working 

 with the fingers through the cover film until it forms a suitable air seal. 

 The fluid should next be gentry worked through the specimen in such 

 a manner that it will displace the larger bubbles and come into full 

 contact with the entire surface area of the specimen. 



Curing and reworking specimen material laid out in the fresh state. — 

 Specimens to which preserving fluid has been applied while in a fresh 

 state ordinarily require prolonged curing under refrigeration. As soon 

 as the cover film has been applied and the preserving fluid suitably dis- 

 tributed around the specimen, the layout should be placed in a re- 

 frigerator where a temperature of between —4° and 4° C. (approxi- 

 mately 24° to 40° F.) is maintained. The time required for curing at 

 this temperature usually ranges from 10 days to 4 weeks, according to 

 the nature of the material and the temperature and humidity conditions 

 prevailing in the refrigerator. When fully cured, the specimen usually 

 has a characteristically shriveled appearance, and all turgid parts 

 become collapsed: at the same time the tissues develop a definitely 

 toughened condition. Remoistening, through the use of wet paper pads 

 or by confinement in a humidifying chamber, is necessary if the pre- 

 serving fluid has begun to harden before the layout can be reworked. 

 The procedure for reworking and the use of the plastic squeegee or roller 

 is the same as under procedure A. Upon completion of the reworking, 

 the waxed paper should be removed and the layout cleaned and dried 

 in preparation for the dehydration step. 



Procedure C — Treating Fresh Specimens in Preserving Fluid 



Bath 



Fleshy specimens, as well as brittle or easily shattered flowers and 

 leaves and any other material that has been found to be unsuitable for 

 the first two procedures should be immersed while in a fresh state in a 

 bath of preserving fluid. . 



Succulent fruits, fleshy tubers, bulbs, corms, and similar bulky vege- 

 table material can in many cases be preserved satisfactorily in this way 



