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518 THE PHOTOGRAPHIC NEWS. [October 30, 1868. not as familiar to photographers generally as it ought to be, and that it is worth briefly re-stating. The object of adding alcohol to the developing solution is, as every photographer knows, not to produce any chemi cal effect or to aid in developing, but to harmonize, as nearly as possible, the physical condition of the developing solu tion with that of the free nitrate of silver on the plate, so that the former may flow evenly over the film without form ing greasy-looking lines, which arise when the two solutions are not in the same condition. The suggestion to which we have referred is simply to carry out the practice, employed with developers, to all the solutions employed in developing or intensifying, a thing which, obvious as it may appear, is by no means commonly done. Whatever quantity of alcohol is added to the ordinary developer should be also added to the intensifying solution, and to the silver solution kept for adding to the intensifying solution. We are here assuming that the intensifying is effected, as it now most commonly is, by means of an iron solution. It will be seen in such case that the application of the developer can be followed by the application of the iron intensifier, or that of the silver solution, without either washing between each application, or running any risk of the production of stains from the repulsion or imperfect mixture of solutions contain ing different proportions of alcohol. The convenience in operating which arises from being able to apply one solu tion after another without washing and without risk will be readily appreciated by practical operators who have not hitherto tried such a simple aid to clean and convenient working. NEW METHOD OF MASKING PRINTS. Some correspondence which has reached us, on the subject of the method of masking prints employed by Mr. Fry, which we described in our last, suggests that we had not made the precise purpose and scope of the operation so clear as we intended; and it is pointed out that unless used with judgment, the employment of a transparent positive as a mask might be made to produce, instead of improvement, a negation of all gradation and modelling. This is perfectly true : but we meant it to bo used in the right way and with judgment, although it seems we did not point out the limitations of its use with sufficient detail and iteration. Let us glance, therefore, at the matter a little further. One of our correspondents points out, very truly, that the thinnest or most transparent part of the mask pro posed will be the points of highest light, and that the lights in a print exposed under such a mask will be the first portions upon which light will act, and that degraded lights instead of increased detail will be the result. As there is something ingeniously erroneous in the argument of “R. F.,” it may be worth while, before correcting him, to make his position quite clear by an illustration. He states that the first effect upon a print of using a transparent positive as a mask will be a degradation of the high lights, and then the gradual impress of gradation, but that the gradation will be in the wrong direction, darker towards the lights, and lighter towards the shadows. Thus, if we print an image of a sphere from a negative, assuming it to have been produced in an ordinary glass room, we shall have a spot of light near the top, gradually merging into deeper shade as the surface of the sphere recedes from the light, the under surface being only relieved from absolute blackness by reflected light. If we then take a transparency from the same negative, and print an image on paper from this transparency, we obtain an image exactly the reverse of that printed from the negative. Instead of a light near the top, we have in its place the intensest black, gradually merging into white as the surface of the sphere recedes, producing, instead of the effect of relief, the effect of hollowness or intaglio. Our correspondent then points out that as this is the kind of image which a print from the mask would present, it will produce just such an effect when superposed on the print, limited only in degree by the time of exposure under such a mask. As we have said, this assumption is so ingeniously wrong that it was worth while to state it fully before correcting it. Ail that “ R. F.” has stated would undoubtedly result if the mask were used as he is assuming it would be ; that is, upon the print after it is removed from the pressure-frame. But it is not, under any circumstances, to be so used. Let it be distinctly understood that it is to be used as masks usually are—practically to modify the character of the nega tive during the progress, or part of the progress, of printing. The negative is assumed to be too hard; to possess too much contrast; to allow some portion to become too deeply printed, so as to bury detail in the shadows before the details in the lights are printed through. This mask will practically reduce the contrast, retarding ths printing of the shadows without impeding the printing of the lights, and so bringing about the balance necessary to produce harmony. There is no danger of the lights being degraded, because they are at all times protected by the dense negative; and there is no danger of inversion of grada tion, as however the mask may modify the passage of light, that light must always pass through the negative before it reaches the print. As we said in a former article, the mask may be worked upon to any extent the photographer may desire, in order to produce special effects; but in order to correct the effect of an over-dense negative, it merely re quires to be a good transparent positive from such negative. Mr. Rejlander, in a private letter, makes a capital sugges tion in connection with this subject, one which would be valuable in dealing with subjects in which the inherent con trast is too great to receive full justice from photography. He suggests that if the collodion film could be safely trans ferred from the glass, a negative giving fine results might be formed by the superposition of two films : one thin and soft, with abundance of delicate detail and half-tone, and the other with more contrast, doing full justice to the more vigorous lights. As there is really no difficulty in re moving the collodion film from the glass, after a very little practice, either by the method described by Mr. Woodbury or others, the suggestion of Mr. Rejlander might easily bo put into operation, and some harmonious pictures produced from difficult subjects. Oritical Jlotices. ON THE RETOUCHING OF PHOTOGRAPHS; A Manual of Instruction in the Perfection of Negative and Positive Photographs, and in Colouring the same with Water, Aniline, and Oil Pigments. By Johannes Grasshoff. (Berlin : Louis Gerschel). In a compact little volume of eighty pages, M. Grasshoff gives us very clear and precise directions on the subject of improving and beautifying photographs. The subject is one upon which the author is well qualified to write, and the simple unaffected language in which his ideas are con veyed to the reader render his remarks easily intelligible to the novice, and awaken a spirit of trust and confidence in his teaching. It is essentially a practical book; and, in the preface, M. Grasshoff informs us that he has, as far as possible, eschewed all theoretical dogmas, and confined himself to the description of methods which have stood the test of many years. He pre-supposes nothing further than a slight elementary knowledge on the part of the student, either in regard to manipulation with the camera, or with the brush ; but remarks that, as a natural consequence, in order to produce perfect results, some skill is necessary on the part of the operator. The volume is divided into eight chapters, treating re spectively of the following subjects :—Retouching on the original; retouching on the negative; retouching of ordin-