DEVELOPMENT, STAND (Fr. Developpement dans les cuvettes verticales ; Ger., Stand entwickelung) This term was applied by Meydenbauer in to a system of developing plates in upright grooved tanks in extremely dilute developers, though the system was first described by Wratten and Wainwright in 1882. It is claimed for this process that the grain of the silver image is much finer than by any other method, that the gradations are truer and the results more nniform. ; in addition to which no visual examination is required, and therefore the plates are freer from fog. On the other hand, unless the developer be occasionally agitated there is considerable risk of peculiar local markings and stains. For many years after its reintroduction by Meydenbauer, extremely dilute solutions were recommended so that the duration of de velopment was prolonged even up to twenty-four hours. Recently, however, a more sane view of the matter has been accepted, and time has been so considerably reduced that it has now practically been merged into " time develop ment." (See " Development, Time.") It is often considered that the necessary in crease in the duration of development is calcu lable from the dilution—that is to say, if a normal developer takes three minutes to obtain a certain density, it will, when diluted ten times, require 3 x 10 = 3o minutes ; this statement is not borne out by careful photometric measure ments, and Wratten and Wainwright have published certain researches on the subject based on such measurements which disprove this assumption. They point out that stand development cannot be considered economical, as most of the commercial tanks require far too much developer ; with 29 oz. for six half plates, after half an hour's development the solution is so oxidized as to be useless. The
idea that a plate may be left in a stand developer for an indefinite time is also wrong ; as is also the theory that a plate which should require only thirty minutes will be as much spoilt in an hour as the same plate developed for six minutes instead of three. It is as important, therefore, to know the correct duration of stand develop ment as that of ordinary development. They further point out that the increase of time required with rodinal is largely dependent upon the amount of air dissolved in the water to make the developer. For instance, a plate that required three minutes' development with : 20 rodinal required forty-two minutes when developed with i: 200 rodinal diluted with air free distilled water, and not thirty minutes ; forty-six minutes with ordinary distilled water, and fifty-two minutes with ordinary tap water. Pyro-soda and glycine are not dependent on the amount of air in the developer, but a ten times diluted pyro developer requires fifteen times the length of development with the strong developer.
dge markings are very liable to occur, due to the plates being too near to the edges and the bottom of the tank, and thus being starved of developer. Plates are also as liable to chemical fog in stand development as in any other kind, and therefore too prolonged development should be avoided or bromide should be added to the developer, in which case the exposure must be increased, and not the duration of development. Zinc tanks should be avoided, as they are very liable to be attacked by alkalis.