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8 THE PHOTOGRAPHIC NEWS. [January 1, 1869. This is well filtered and poured upon the sensitive plate, after being carefully washed. On this is poured the 1 per cent, solution of gum, mixed with 1 per cent, of sugar- candy recently prepared. Everybody will understand that on the application of the gallic acid to the sensitized film every trace of free nitrate of silver should be removed by a very scrupulous washing of the plate. M. Gordon washes the plates three times in distilled water, then allows them to remain at least one hour in ordinary water, previously to rinsing them again in distilled water and applying the preservative coatings. Major Russell asserts that an inter mediate washing in salt water is necessary. With my ordin ary process, which consists in washing the plates with a copious supply of spring water by means of a rose, both before and after their sojourn in the rain-water bath, I have never experienced either stains or any other misfortunes. I shall not speak hero of M. Gordon’s iron developer formula, as it is well-known, and has already been quoted in the Bulletin; but I ought to remark that this developer is a very excellent one, and particularly suitable with dry plates, for the addition of silver has but a very slow effect upon it, and the mild and progressive action exerted by it upon the more or less lighted portions of the image gradually reproduces all detail, without the appearance of stains or any other defects. I have employed this same gelatinous solution of sulphate of iron with similar success in the development of plates prepared by the coffee process. In a publication relating to M. Gordon’s new processes it has been affirmed that it would be advantageous to mix together the solutions of gum and gallic acid, in order to form a more homogeneous coating, the materials being used in the following proportions :— Water ... ... ... 100 cub. cents. Gum* ... 4 grammes Sugar-candy 1 „ Gallic acid } „ This modification, which would effect an economy in labour and time in the preparation of plates, had already been in dicated and approved of by M. Manners Gordon, who ex plained, however, that he had not adopted it on account of the dark colour which was produced on mixing the gum and gallic acid together, fearing that the tint of the pre servative would exert a prejudicial effect upon the length of exposure. This is no doubt a question deserving of study, for it would be easy to mention preservatives as transparent and colourless as water which require a very .lengthened ex posure, and others of a yellow and red colour which are very rapid in their action. I should very much like to hear the ideas of some of my colleagues upon this subject.t En attendant, I have experimented with the mixture of gum and gallic acid, and have obtained some very satisfactory results ; in fact, so pleased have I been with them, that were my investigations somewhat more complete, I should not delay in recommending the employment of this modifica tion. The exposure, far from being lengthened, appeared to me at least quite as short, andjthe employment of the deve loper in this form recalled to mind certain effects which are obtainable in the simple gum process, and which may be observed in the specimens which I have enclosed with these remarks. It has been stated that M. Manners Gordon recommends in the preparation of his plates a mixture of different com mercial collodions. This is not the case. M. Gordon has merely stated that any English collodion in the market may be employed, if an addition of bromide of cadmium to the extent of 2 grains per ounce were made. This advice I have followed in regard to Mawson’s excellent collodion, which I am at present using. • M. de Constant has called our attention to an error in the formula as stated in the Bulletin, in which the gum is stated at 1 gramme instead of 4 grammes.—En. Photo. News. t Mr. Gordon, in a communication to our Yeak-Book for 1869, states that, after some experience, he does not find any disadvantage from the dark colour of the mixed solutions.—Ed. Photo. News. In the majority of cliches which I have prepared accord ing to the Gordon process, I discovered, after washing and fixing, minute holes in the skies of the negatives of different forms, which I attributed solely to the imperfect filtration of the gallic acid solution; for in the preparation of waxed paper, in days gone by, it will be remembered how difficult it was to dissolve the gallic acid and to render it limpid. To remedy this inconvenience, and to have a solu tion always good and ready, I recollect adopting a sugges tion of Mr. Crookes, who proposed the employment of an alcoholic solution of gallic acid, which was afterwards to be supplemented with water. Possibly a gallic acid solution of this description might be used in the Gordon gum process. As regards the preservative qualities of the mixed gum and gallic solution, it may be kept to the last drop by the addition of a small quantity of essence of cloves. I have already said that in the gum dry process, as is the case with most dry plate processes, it is necessary that the plates should be dried with the utmost care, and every glass should be subjected to a rigid examination before being put away into store. Many curious facts which I have recently noticed convince me that the drying of plates is a subject to which sufficient attention is not given. MM. Baratti, Russell, and Carey Lea have already made some interesting communications on the subject, but they have not been re garded with the attention they deserve. In a future article I myself' propose to say a few words touching this important point. ON THE PRODUCTION OP PHOTOGRAPHIC ENAMELS. MM. GEYMET and Alker have just issued their promised volume on this subject. It is described by the authors as a practical treatise for the photographic enameller, and is stated to contain the whole secret of the production of permanent pictures upon glass and porcelain. We make a few extracts from the preface :— “ It was not our intention to produce a scientific treatise ; we should in that case have had to describe many things irrelevant to the subject in hand; it would have been necessary for us to have entered into the details of the art of enamelling, to speak of the importance of ceramic porce lain, &c.; and, once on that subject, we should have been in a fair way of producing a long, and probably uninteresting, volume, which would not by any means fulfil the object we had in view.” “ We shall be silent, therefore, upon this subject, as also upon the origin of glass and enamel, merely saluting, en passant, the names of Lucca de la Robbia, Bernard de Palissy, Bollger, and Wedgwood; for in a practical work one ought not to stray from the beaten path to touch upon historical and scientific subjects, excepting where such a course is absolutely necessary. Thus, if the reader wishes, for purposes of recreation or otherwise, to bring photo graphic enamelling to a successful issue, ho need only follow our book and adopt our formulae, and he will then find that this interesting branch of industry does not present any serious difficulties; for he may rest assured that any mechanical operation which is successful in the hand of one person may be performed by anybody who possesses a moderate amount of skill and taste.” “ The aspirant must not be scared away by apparent difficulties, for any one reading this work, and not essaying the process, may believe in the impossibility of obtaining perfection. To trace an image of extreme delicacy with a crude badger pencil, which is not that of an artist, by means of vitrifiable powder, upon a glass which has been exposed to light for a few seconds ; to recover the powder upon a film of collodion, and to transport the whole to a plate of enamel; to destroy the collodion without regard to the image which it is impossible to fix, to wash the enamel powder several times in water, to introduce the plate into
