PHOTOGRAPHY.

Auckland Star, Volume XLIV, Issue 28, 1 February 1913, Page 15

PHOTOGRAPHY.

HYPO UN AND OUT OF PLACE. While hypo is, of course, a very necessary chemical in photographic" opera- I tions, there is no doubt that a very large number of failures in negatives and in prints may be traced to hypo in the wrong place. Failures due to this cause are frequently more in evidence during warm weather than during the cold of winter, and this for several reasons. One is that crystals or solutions spilt upon the flooi or bench do not dry up in the cold 01 damp atmosphere sufficiently to fly about in powder form, as happens when the air is dry and hot. A frequent and often unsuspected cause of fogged prints lies in the contamination of the developer by minute traces of hypo conveyed there by the fingers or splashed into the dishes or graduates. There are many ways in which this contamination may be brought about, and it can only be avoided by carefulness and cultivating a habit of looking upon hypo as a deadly enemy. ] The hypo dish should always be close i to the sink, and when taking plates or 1 prints out of the solution for examina- ! tion, before holding them over the ' bench or floor, rinse well under the tap, so as to remove all surplus solution; any droppings then falling will contain the minimum quantity of the salt. Also rinse tbe fingers well when having had them in contact with hypo before handling anything else. A fault that is very common, and one which gives rise to innumerable mysterious markings and stains, is that of wiping tbe fingers upon a towel, without previously rinsing them. This, of course, is done usually without consideration, and a moment's thought Is generally sufficient to show how prolific a source of danger such action readily becomes. The towel may be perfectly clean at the start, and yet if hypo is continually being left upon it from the fingers it becomes more contaminated each time it is used, and if the finpers are wiped | upon a towel so contaminated it cannot but be seen how easily hypo will be carried into the developing solution or be left upon the sensitive film. When a print is being developed, it is an impossibility to prevent the solution touching the fingers, which, indeed, as a general rule, hold the plate or paper down in the developer, and the slightest trace of hypo touching the .-ensitive film during development will produce black mr.rks, and the more readUy the stronger the developer, especially when metolhydroquinon is used. This may serve to cxphi'n a good many failures in the production cf gaslight prints, the latter papers usually requiring a more concentrated developer than ordinary bromide. When benchroom is limited, it is a good plan to have a separate board, with battens on the back, and always use that to cover the bench with when handling plates and papers, as when filling in slides. Having the battens on tbe back of the board ensures that the samei, surface is always uppermost, and if removed and placed safely immediately after use is always kept free from risk of contamination. If the same bench is used alike for developing and firing operations, as well as for handling plates, etc., there is always the risk of something from the bench being carried to the sensitive film, and this risk is greatly intensified if a dusting brush is used. This being lad down upon a chemically dirty bench will pick up anything that is there, and it chen carries it across the plateLike many things, hypo is a good servant, but a bad master, and nmst be kept rigorously in its proper place, out of the developer and away from the ■ sensitive film until the proper time. It is hardly possible to be 'too careful ir washing the fingers, after handiini: j plates in the fixing bath, before proceed I rn_- to develop more plates, especially I*' under-exposed plates arc being deoped with a powerful developer.