Equipment for Larger - Scale Working

The individual users of a relatively large amount of film can usually cope with processing in multitasks. Where processing is undertaken for more than one photographer or where sheet film is regularly used, a rather larger installation becomes necessary. The general practice in this case is to use large box like tanks with a capacity of about 7 or 15 liters. The tanks are available from many manufacturers in various forms and with their own individual refinements. Basically, however their construction is simple. The main requirements are that the material from which they are made should be reasonably robust, resistant to all photographic chemicals and totally opaque. A typical gas burst agitator to be fitted to IS-liter or larger tanks consists of a frame of six pipes with small perforations through which an inert gas (usually nitrogen) can be forced at intervals. The method is used for sheet film but is not considered suitable for roll and 35 mm films on spirals because the gas bubbles could be trapped between the closely-spaced film surfaces. The duration and frequency of the burst can-be critical for some processes. The duration is rarely greater than two seconds because a longer burst might create flow patterns that would lead to streaky or uneven -development. The frequency of, or interval between, the bursts depends largely on the process and the amount of agitation required.