PHOTOGRAPHIC NOTES

Evening Star, Issue 21316, 21 January 1933, Page 4

PHOTOGRAPHIC NOTES

[By Panchiio.]

In this column will appear week by week news and notes of interest to amateur photographers. It is intended to be of use to both sections of that large fraternity, those who are on speaking terms with facts, forraulre, and darkroom lamps, and also to those who frankly confess themselves as mere “ button pushers.” To the former it is hoped to rendei a technical service that will be useful, and to the latter " Panchro ” hopes to give an increased pleasure in the use of a camera. Inquiries should be addressed to “ Panchro," care of this office, enclosing a stamped, addressed envelope for reply. Inquiries of general interest will also be answered in this column. WITH THE BEGINNERS. There is still considerable interest taken in the self-toning varieties of prints. Self-toning paper marks a step forward from the earlier forms of printing when printing out paper was used. Tim actual printing with the above papers is the same, but subsequent operations vary considerably. The selftoning papers have embodied in the emulsion the requisite chemicals for producing the warm sepia-coloured prints with which no doubt you are quite familiar. The old P.O.P. required to be toned in a solution containing gold chloride.

For self-toning paper a good strong negative with adequate detail is required. Place the negative with the mask in the printing frame together with a piece of paper—emulsion side of film and paper to he in contact. The frame is now stood out in the daylight and the print inspected from time to time by lifting one half of the hinged back of the printing frame. Under no circumstances is the frame to be stood out in the full glare of strong sunlight, as this will spoil the even gradation of the picture. It is best to place the frame on the shady side of the house where the sun cannot get at it. A print which comes up slowly but steadily usually lias the best tones. Carry the printing on until it is somewhat darker than the finished print is wanted, and then place it in a dish of clean water for a few minutes, after which it is transferred to a plain hypo bath. An instruction sheet is enclosed with each packet of paper, and the strength of solution and time to leave the paper in it are always indicated on this sheet. One word of warning: Never use acid hypo on these papers. As a print done by this process is gradually built up in density, the control over it is very good. Thin parts of the negative can be shaded to hold them back. Thin tissue paper will be found excellent for this purpose. Should the colour of tho prints he thought too warm, it can he considerably reduced by immersing in a bath of saturate salt solution. This will introduce a certain bluishness into the colour which is very pleasing. Altogether, self-ton-ing paper is very easily handled, and makes charming little prints when suitable negatives are available. It can be procured in a variety of surfaces, cream and white, and in both normal and vigbrous grades.

VARNISHING NEGATIVES. Tho object of varnishing is to protect the gelatine film from scratches, damp, etc., and to prevent silver staining duo to the absorption of damp by both papers and negatives. Hot Process.—The negative is warmed to drive out all moisture, and then allowed to cool. Tho negative need not be hot when tho varnish is applied; it is much more important that' the negative be dry. Hot negatives may crack when cold varnish touches them, and tho varnish may dry with marks and streaks, while a damp film will cause the varnish to dry milky, fish-scale markings possibly appearing later. The negative is held film side upwards in the left hand, the bottle of varnish in the right, and a pool poured into the centre of the plate and allowed to spread almost to the edges; then the negative is tilted slightly until the varnish flows to the top right-hand corner, next to the left, then to the bottom left-hand corner, and finally to tho bottom right-hand corner, from which corner the superfluous varnish is poured hack into the bottle, holding the corner of the negative in the mouth of the bottle, and “ see-sawing ” the negative to prevent streaks. The negative is next heated before a fire, or over a gas burner, until the coating is hard and dry, it being kept on the move to obviate the formation of streaks.

Cold Process.—ln applying cold varnishes the chief consideration is absolute dryness. The varnish is applied in the manner described for the hot process, although with care it may be brushed on sparingly with a soft brush. The negatives are set aside to dry in .a place whore dust cannot form on them. Films may be immersed bodily in some varnishes. Varnish Substitutes.—Various substitutes for varnishing are known. One method is to place a very thin celluloid printing paper, but this is a protection only during printing. Another method is to harden the film with tannic acid and alum. BLISTERS. Blisters appear at times upon all makes of plates, films, and papers in the manufacture of which albumen or gelatine is employed, but the papers most subject to the trouble are albumen and bromide. The principal cause of blisters is tho use of a too strong " hypo ” bath, rapid washing, excess of, alkali in the developer, and the difference in temperature between the developing, toning, or fixing solutions and the washing water.. The blisters usually appear when the plates or papers are being washed after fixing. It is a curious fact that fewer blisters appear where ordinary tap water is used than where soft water is employed. It is, however, the fixing bath that usually needs attention when bromide and gaslight papers aro prone to blister. The fixing bath is freshly made with cold water, and hypo should not ho used immediately, the temperature of such a solution dropping almost to freezing point, and, of course, many degrees lower than the temperature of the washing water used before and after; lienee tho expansion of the wet gelatine, which is very susceptible to temperature, in the form of blisters. If a fixing bath is needed quickly it should

be made with hot water, and used when the temperature has fallen to the level of the washing water; or, if cold water is used, the bath should be mixed some considerable time before use, in order that it may have time to rise in temperature. When care is not taken about the temperature of the bath, blisters may be prevented by allowing the washing water to run gradually into the fixing bath while the fixed prints remain therein. The water gradually replaces the hypo, the difference in temperature (if any) is gradually made up, and the expansion of the gelatine is too slow to do any harm; this method, too, largely prevents blisters due to the use of a strong fixing bath. The use of an acid fixing bath is widely advocated for the prevention of blisters on bromide papers and negatives. Any formula will serve, but that containing hypo and metabisulphite will bo found best. Another plan is to soak the prints previous to, or immediately after, fixing in a 20 per cent, solution of formaline and then to wash well. There is really no satisfactory cure for blisfgj’s when once they have appeared: pricking the paper at the back with a pin for the purpose of allowing the air to escape from the bubble has been advised, but the loosened film never becomes properly attached to the .paper, and frequently peels off when dry. Another plan is to squeegee the blistered print upon cleaned ground glass and strip when dry; but, as in the previous remedy, the blisters invariably scale off later.” Information given above on preventing blisters applies equally well to negatives and bromide and gaslight papers. Blisters but rarely appear on negatives, but when they do the negatives should be soaked in methylated spirits and dried; a more general trouble with plates is “ frilling.”