The Cine Technician (1935-1937)

Aus^ust, 1935 The Jnunial of the Association of Cine-Tech)iicians 39 STUDIO FILM LABORATORIES LTD. TITLE MAKERS TO THE BRITISH FILM INDUSTRY SENSITOMETRIC LABORATORY CONTROL SPECIAL PROCESSING & OPTICAL PRINTING TECHNICAL PROBLEMS INVITED 80-82 WARDOUR ST. LONDON, W.l GERRARD 1365-66 Purity in Chemicals — continued from page 38. cause, the chemical manufacturers were asked to give their opinion, and they made the suggestion that it was due to small particles of rust from the water supply. Flaimel bags were immediately tied to the taps and the water allowed to filter through them, and at the end of a few days the bags were examined and consternation caused by the amount of dirt that had deposited in them. The installation of a new set of pipes ended the trouble. Only a small cause, but sufficient to give a lot of trouble ; so it is with any impurity which can upset the chemical reaction in a minor or major manner. Lack of cleanhness will cause endless trouble, as will also a too strained attempt to economise ; for it must be remcml)ered that a bath of chemical solution whilst functioning will absorb other chemicals from the senistised material, and these in conjunction will form other salts, some of which may be insoluble and settle on the film. An instance of this type occurred in a dark room where the operators ought, by the amount of work going through their hands, to have known better. When a bath was working slowly, instead of making a fresh one, a small (]uantity of the chemicals was dissolved and the .solution poured and stirred into the tank as a replenisher. The stirring, of course, set all the precipitation of the "rogue" salts floating and, in due course, trouble became noticeable by sundry curious and irregular lines and marking. The film was first blamed and then the chemicals. On examining the tank, a rather bad smell was noticed, and after enquiries, the top liquor was syphoned off and a very heavy deposit of sludge was found at tlie bottom, which was due partly to overworking the solution, but mostly to laziness and the unclean habits of the laboratory. Chemicals when pure are at the highest efficiency point, and their reaction on the emulsion is therefore the maximum. Any lowering of the purity standard, either by "foreign" matter, over-working, exposure to air, or mistakes in weighing — which throws the formula out of balance — will reduce the efficiency and bring about a loss either in the quality of the work or amount which can be turned out. Have your chemicals pure. Never mind those few pence lower per pound which someone else offers you to get your order. It may not pay ! The greatest care is necessary in the dispensing of developing and fixing solutions. Those responsible should work in a secluded spot, so that no chemical dust or fumes can come into contact with film emulsions. Vats should be fitted with air-tight lids to protect the solutions against oxidisation. Remember that the emulsion maker uses only the purest chemicals for the tests on which he bases his formula. The Film Society \ L.\RGE number of film technicians are members of the Film Society. It has been the practice to offer special membership rates to technicians and previously this has been at the rate of 15/ for the season. Details of next season's programme, and membership rates will not be available until early September. It is, however, hoped to extend similar privileges, and it is trusted that a large number of A.C.T. members will take advantage of these. All members who are interested should write Miss J. M. Harvey, Secretary, The Film Society, Ltd., 56 Manchester Street, London, W.l, who will forward full details as soon as available.