Transference shadow material

An excellent review of freeze fracturing is found in a chapter by McNutt [576]. The method has been described for the preparation of biological membranes. An older, improved version of the method was described by Steere [577] and Moor et al. [578], and a review of the method and application to membranes was described by Branton [579]. The method involves cementing a 1-2 mm piece of the material onto a copper disk with gum arabic dissolved in 20% glycerin and then transferring the material to liquid Freon 22 (chlorodifluoro-methane). The specimen is fractured with a cold knife in a vacuum evaporator, and it may be etched prior to replication. A replica can be cast on the surface of the hydrated material at low temperature in a vacuum [576] for examination in the TEM or the replica, or the shadow cast specimen surface, can be examined directly in the SEM. 

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