Replica Studies of Bulk Clays

TLDR: In this paper, the surfaces of some bulk endellite clays were examined by means of collodion, silica, and preshadowed replicas, and the best results were obtained with the preshadowsing technique which employed a shadowing layer of platinum backed by a layer of evaporated carbon or by Parlodion.

Abstract: The electron microscope examination of the surfaces of bulk clays by replica techniques is difficult because of the porosity of the clays and the necessity of using hydrofluoric acid to dissolve the clay from the replicas. The surfaces of some bulk endellite clays were examined by means of collodion, silica, and preshadowed replicas. Collodion and two‐step silica replicas were unreliable and difficult to use because of penetration of the collodion or plastic into the pores of the clay. Collodion strippings were of some value in removing layers of clay particles from the surface for direct examination in the microscope. Best results were obtained with the preshadowing technique which employed a shadowing layer of platinum backed by a layer of evaporated carbon or by Parlodion. Micrographs of replicas prepared by the latter technique show the surface of a highly porous endellite clay to consist of tubes in various orientations.