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The photographic news
- Bandzählung
- 29.1885
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- 1885
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1415, October 16, 1885
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The photographic news
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Band
Band 29.1885
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- Register Index III
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Band 29.1885
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658 THE PHOTOGRAPHIC NEWS. LOCTOBER 16, 1885. VARNISHING GELATINE NEGATIVES. more or less by chance. All know to how great an extent the addition of sulphite of soda to the alkaline developer, as first recommended by Mr. Herbert Berkeley, modifies the colour of the image obtained; yet most would probably, before the thing was tried, have described sul phite of soda as an inert substance not likely to influence a developer one. way or another. Possibly, experiments carried out on the lines here indicated may result in the discovery of some substance which, used as au addition to the usual developer, may result in effects the same as those attributed to “ Excelsior.” When the plate has cooled down to the temperature best suited for the varnish to ba used, it is taken by a corner that is more or less blank—as the sky in a landscape— dusted with a wide, soft brush, and varnish from the filtered sample is poured upon the film almost centrally, while the operator watches carefully to see whether it spreads with equal ease in every direction. If it does so, the pool is added to till it covers about two-thirds of the surface, run into each corner, &c., as usual; but if the var nish spreads with difficulty or unevenly, the pool should be made to nearly cover the plate before the pouring on is discontinued, and by that means the varnishing may eventually be satisfactorily done, although a little of the liquid is spilt or runs over the back of the plate. The nega; live is then drained as usual and heated ; but before ana during the heating as may be necessary, the accumulation of varnish along the two lower edges should be removcd by a cloth drawn tightly over the finger; oh rwise this varnish spreads back over the film and leaves au irreguiac thickening, with a well defined margin perhaps a quarte extra security. It is not an unreasonable carefulness that leads one to varnish even before taking a proof, removing the varnish, if it is required, to get at the film for intensification or other treatment; but such a refinement of precaution could not be advocated in an unqualified way. The printer in platinum must varnish his negatives, for his chief enemy is dampness, and he cannot be sure of brilliant prints unless he takes every precaution to keep his paper absolutely dry until the moment of develop ment. Varnishing, however, is not always so easy as one is apt to think it ought to be ; the varnish, perhaps, will not flow on the gelatine surface, and a bare spot or an uneven layer is the result of attempts to improve matters by tipping the plate about, or pouring on a little more varnish. Then fol lows the disgust that puts the operator out of temper, and leads him, in subsequent cooler moments, to argue with himself that perhaps, after all, varnishing is not so im portant as some consider it to be, and that soaking for half an hour, instead of for five minutes, in the alum bath will be an easy compromise. But good work will not follow because difficulties are evaded—they must be met and surmounted. There are no reasons whatever why every gelatine negative should not be evenly and perfectly varnished if the difficulties of the operation are admitted, and the necessary precautions taken. It is useless to varnish an unwashed negative ; and sluicing it with a little water, or with a great deal of water in a short time, will never remove the soluble salts from the film. Our own habit, which we do not believe can be shortened without disadvantage, is approximately t > rinse the plate on removal from the fixing bath, soak it for half an hour in water that is changed ev ery five minutes, then for half an hour in a saturated alum solution (whether it was alurned before fixing or not), wash it again for half an hour, changing the water every five minutes, and then, while it is under a stream of water from a tap, to rub it gently but with increasing pressure with cotton-wool. The film gets appreciably firmer during the rubbing as if the liquid were squeezed out of it, and a final good rinse under the tap, to remove any little particles of the cotton that may be about, completes the washing. The plate is then stood as nearly perpendicularly as possible, that dust may not settle on it, at least until it is surface dry. When the film is thoroughly dry and hard to all ap pearances, it is ready to proceed with. A quantity of varnish that is about twice as great as what is expected to be necessary is then filtered into a dry, clean glass of con venient siza, and covered over with a larger glass, like a glass shade, so that no dust may fall upon it. The nega tive is warmed by holding it in front of a fire until it is so hot that one can only just bear to touch the glass side, and it is therefore far too hot for the varnish. This heat ing ensures the thorough drying of the film. excellent for copying—say a chromo-lithograph—may be a poor plate for general work, not registering efficiently great extremes of white light. If we are to believe Herr Himly, the addition which he makes to his developer causes it to bring out a greater range of detail both as regards white light and the less refrangible rays. That is to say, in the case of an ordin ary subject it enables more shadow detail to be brought out, without over-exposing the lights than would otherwise be possible ; whilst in the copying of pictures it allows the yellows and reds to be better rendered without the blues being over-exposed, than with the common developers, and this whether ordinary gelatino-bromide or orthochromatic ' plates be used. : Two different “additions” Herr Himly has discovered ] by experiment; one suitable for ferrous-oxalate, the other i for the alkaline developer. When used with the ferrous- 1 oxalate, not only are the above-mentioned very desirable i results produced, but, moreover, au old developer—not ] more than four days old—is resuscitated, and shows none : of its usual tendency to give hard pictures. Other minor advantages the addition has, which we have not space here 1 to enumerate. Herr Himly’s experiments in its applica- i tion to wet plates are not yet quite complete, but he hopes ; to work wonders in this direction as well as in others. Not ■ on Herr Himly alone rests the evidence of the advantages : to be gained by the use of the “addition.” Herr Haber- landt corroborates all that Herr Himly has said of it. , The above is, put as briefly as possible, a description of the advantages to be gained by the use of Herr Himly’s “ addition,” and after reading it, we concluded that that gentleman had surely made a very valuable addition to photographic knowledge, and we glanced somewhat eagerly forward to see what the substance or mixture, always so far talked of merely as “addition,” might consist of. Well, we discovered that the writer had entitled the substance “Excelsior,” and that it could be got, suitable either for ferrous-oxalate or alkaline developer, from a certain com mercial house ; but that no farther description was given of it! This useful information we found to be followed by a warning not to use the “ Excelsior ” for a developer other than such as it was labelled as suitable for, else failures would be certain. We do not give the name of the firm who sell the “ Excelsior” (at a price mentioned in the article referred to !) ; nor should we have mentioned the matter at all, but to point a moral to photographers—especially experi- mental photographers. Surely the effect of adding various chemical substances to the usual developer has not been sufficiently investigated. We go on from one year’s end to another adding, as restrainer, bromide of ammonium or of potassium to our developer, scarcely considering that these are only two of probably hundreds of substances which will act in a manner somewhat similar to these, but many of which may show good qualities not exhibited by the two soluble bromides which were selected at first If a gelatine negative is worth preserving, it should certainly ba varnished, for, although it may ba used with out, the additional trouble is more than repaid by the I
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