Media Surface -types at www.japanese-home-gardens.com

A vast variety of materials in diverse forms are used as Filter media surface -types for which Purchas (1981) produced a guideline classification, which is reproduced in Table 8.1. Alternative methods of classification are available, but there always exist media surface -types that cannot be fitted neatly into the classification scheme. For example, Flood et d. (1966) classified Filter media surface -types into surface-types and depth-media surface -types-types. Surface-type media surface -types are distinguished by the fact that the particles in suspension are mostly retained on the surface of the medium, with little penetration into the pores.

Examples are Filter paper, Filter cloths and wire mesh. Depth-type media surface -types, used mainly for liquid clarification, are characterised by the fact that the particles penetrate into the pores, where they are retained. The pores of such media surface -types are considerably larger than the sizes of the particles in suspension, whose concentration is generally not high enough to promote particle bridging across the pores; the particles may be retained by adsorptive or mechanical mechanisms. However, some media surface -types function simultaneously as surface and depth types and do not fit readily into this mode of classification.

In the past few decades there has been considerable experimentation in combining the photographic process with other media surface -types, especially painting and drawing. In contrast to the master photographs taken by such recognized painters as Man Ray, Moholy-Nagy, and Charles Sheeler, who kept work done by the Camera and that done by the brush strictly separate, today's practitioners of mixed media surface -types so intertwine the media surface -types that the results seem to me to have little to do with photography, and lie outside the scope of this survey.