The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186200003
• PURL: http://digital.slub-dresden.de/id1780948042-18620000
• OAI: oai:de:slub-dresden:db:id-1780948042-18620000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
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• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

THE PHOTOGRAPHIC NEWS. [April 25,1861 addition of ether, or your plate will be covered, during the de velopment, with a multitude of blisters about the size of a pin’s head, which spoil the negative. Now the use of this kind of collodion greatly reduces the sensitiveness of the plate because sensitiveness depends, in great measure, upon the state of the excited collodion film. In our new process this objection does not occur, because we commence with the most sensitive and creamy cadmium collodion, and yet avoid all chances of blistering by using a suitable second film. In the next place in the Taupenot process, the second nitrate bath is strongly acidified with acetic acid, which is added in about the same proportion as the silver. This renders the second film insensitive. But in our process the second nitrate bath contains very little acetic acid, and it is not impossible that even that little may be omitted altogether. If, therefore, our process resembles that of Dr. Taupenot in having a double film, and a double excitation, it still differs from it in two very important points. In a word, we have taken the Taupenot process as a basis, and have modified it in those particulars in which it was evident that sensitiveness was sacrificed, through mistaken notions of what was right and necessary.” The details of the process follow, but as they are modified in a subsequent number, we shall quote them from the latter, in which also some further affirmation of the principle is given:— “ Before giving minute directions, we will endeavour to ex plain the principle upon which we believe the rapidity of a dry plate to consist. It is in the retention by the film of a certain small quantity of free nitrate of silver, this small quantity of nitrate being entangled or combined with a coating of organic preservative applied to the iodized collodion film. Our experi ments do not permit us to believe in the possibility of employing any other principle in the production of a rapid dry plate, and we cannot endorse the opinion expressed by Mr. Bartholomew, in a communication which we have copied from the News into the present number, or encourage our readers in the hope that they will obtain any good result in that way. If you take an excited collodion plate from the nitrate bath, and wash it thoroughly in distilled water, it is notorious that you reduce the sensitiveness immensely, and it is equally certain that the lost sensitiveness cannot be restored by the application of any of the known pre servatives to the film. At the same time it is not necessary for the preservation of the original sensitiveness that the nitrate of silver which remains upon the plate should be of the same strength as the nitrate bath. If the excited plate is removed from the 30-grain nitrate bath in which it was excited, and im mersed in another of only one-third the strength, the sensitive ness will remain about the same, and it will only become neces sary perhaps, in some cases, to add a little silver to the developer to give the necessary intensity to the blacks. “ Assuming then the truth of the above principle, our object has been to ascertain the best means of allowing a sensitive plate to dry with a little free nitrate of silver in it, and yet to keep well for a few days, and give clean, good negatives. “ There are three ways of accomplishing this object:—• “ 1st. You may apply a very thick coating of iodized collo dion to the plate—excite it thoroughly by a prolonged immer sion in the nitrate bath—then dip it into a 10-grain bath of nitrate of silver, slightly acidified with acetic acid (say one drop to the ounce of bath), and then pour a preservative over it and let it dry. A plate prepared in this way would closely resemble in its appearance and properties one of Dr. Norris’s rapid dry plates ; that is to say, if freshly prepared it would bo as rapid as wet collodion, and would give a bluish-black picture, with a slight tendency to greyness in the lights, if the development is pushed too far. In this process the drop of acid to the ounce in the second bath is for the purpose of making the plate keep better; and the use of the preservative is to combine with or entangle the free nitrate, so as to prevent it from attacking the iodide of silver in the film. A mixture of honey and gum arabic, dissolved in water, seems to be a good preservative for this pro cess. A thick film of iodized collodion is recommended in pre ference to a thin one, because it will hold more material, and is always more sensitive. The way to get a thick film is to use collodion containing a great deal of pyroxyliuc, made at a high temperature, and very soluble; or to coat the plate twice with collodion. “ 2nd. Coat the plate with iodized collodion in the usual way, that is, so as to get a film of the common appearance, and not a thick one. Excite the plate, and wash it thoroughly with water. Pour over it an iodized preservative, and let it 0 It is now insensitive to light, and may bo put away • for use at any time. In order to excite it a second time' it well before the tiro, and then pour over it iodized collol as before, and excite it in a 30-grain nitrate bath, contaiz one drop to the ounce of acetic acid. Wash, as in the process, in a 10-grain nitrate bath, let it dry, and it is T for use. • “ A plate prepared in this way, with a double coating of' lodion, looks just as creamy and solid as a piece of 1 glass, and the flame of a candle looks dull and red thn it. The object of the preservative intervening between two films is to prevent the second coating of collodion M attacking and dissolving the first. It also entangles the! nitrate. Iodized gelatine solution may be used for the F servative. Say 4 grains of gelatine and 2 grains of iodid potassium to the ounce of water, which is quite strong enoF “3rd. This is simply a modification of the Taupenot^ cess. Coat the plate with collodion of the usual density, 2 excite in the usual way. Wash thoroughly, and pour ovet‘ plate the following preservative :— ozs. grs. y “ Dissolve the three last substances in the water made 3 1} 10 10 20 Albumen Water Honey Gum arabic ... Iodide of potassium then strain the solution into the albumen, and beat all up* stiff froth. When settled it is ready for use. The objed adding the honey and gum arabic to the albumen is to pre" blistering of the film, and the proportions given above* nearly the same as those used by Mr. Macpherson, of Rorb his albumen process. The plate is now insensitive, and ma, put away for use as required. “ In order to excite it, dry it first before a hot fire, and dI ] into a 20-grain nitrate bath for half a minute, and afterv into a 10-grain bath, both baths being being slightly acid with about one drop of acetic acid to the ounce, as before. T put the plate away to dry, and it is ready for use. “ Whichever of these three methods is employed, the plol, as sensitive as an ordinary wet collodion one, and instantan. views of breaking waves, &c. may be taken upon it when 0 . and after it has been prepared some hours or days, accordins ; the season. “The mode of development may either be that recomme” by Dr. Hill Norris, viz., by first moistening the plate, and pouring over it the pyrogallic developer, with a few dW? nitrate of silver added, or it may be developed thus :— “ Without first moistening the plate, put it into a dish 0 taining some very weak pyrogallic acid with very little s0 acid, and no nitrate of silver. Let it remain in this unt/ the details are faintly visible, and then intensify in the u” way. Citric acid is perhaps less liable than acetic to oblite the imago produced by light, and one grain of citric acid* pint of weak developer might be enough to use. The imo§, at first brought out by means of the free nitrate which # tained by the film. If the plate had been thoroughly wasbl would be absolutely necessary to add nitrate to the develop no image would appear. Fix with saturated hypo, and fini® the usual way. “ The first and second of these three methods are rather! rapid than the last, and give softer negatives, but they arc W liable to become veiled in the development. The last p"® gives cleaner pictures. a “ In working with process No. 3, the tourist would takewi him a lot of plates in the first stage of preparation, andai nitrate bath for the second excitation and washing. Son' his plates he would prepare as rapids, in the mannen scribed, and the others as slow ones, by giving thov thorough washing. This he would do from time time *jj wanted them, and in the meantime the rapid plates "v keep two ortliree days, and the others as many weeks, a plan would bo a groat gain upon wet collodion, and the SHH would be better selected, and the negatives quite equal in v lity, if not better. The time is not far distant when wet6 dion will be altogether given up for out-of-door work, wW , the exposure be long or instantaneous. Let us all stmvt hasten the arrival of that good time, and give a now imJ to photography, and render it a tenfold more attractive P | to the amateur than it is at present.” APR REML IsDIA-B been m graphe last mi of my i pale of no sho] procun obtain village ID exc tient w many I The more r Well, larger made and th severa both f the si pieces, the bi settled think cient. "pon must Ha A line pieces of eae onto and t mean of th Very ] Sever thick surfat a nici little easy are w then glue is nc suffic or la the s coats joint