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THE PEOTOGRAPEIC NEWS, VoL. XXVII. No. 1313.—November 2, 1883. CONTENTS Photographic Tracing Methods 689 distortion in Portraiture G89 rractical Notes 0,1 Retouching. By W. D. Ashman GOO she Photographic Exhibition 692 -he. Dent du Gant. By Professor W. F. Donkin, M.A., F.C.S 693 A Dictionary of Photography 694 French Correspondence. By Leon Vidal 695 Notes C96 609 700 701 703 704 704 PAGE .. 698 .. 699 Patent Intelligence An Autumn Ramble in Shropshire. By II. J. Palmer..*tr**... Among the Mountains with a Camera. By Professor W. F Donkin, M.A , F.C.S Correspondence Proceedings of Societies Talk in the Studio To Correspondents The Photographic News Registry PHOTOGRAPHIC TRACING METHODS. We have received from the publishing house of Liesegang, in Dsseldorf, a very compact and useful handbook* of such photographic methods as have proved to be of prac tical value for the direct reproduction of tracings or writings, and feel sure that some particulars regarding these processes will be acceptable to our readers. The most important of all photographic tracing methods is the cyanotype of Pellet, a process depending upon the reduction of an organic ferric salt to the condition of a ferrous salt by the action of light; and so far it is analogous to the platinotype. Ferric compounds react with ferro cyanide of potassium to form Prussian blue, while ferrous compounds form a white salt with the same reagent. If the prepared paper of Pellet were introduced into the ferrocyanide developer without exposure, it would become blue all over, in consequence of the uniform deposition of Prussian blue ; but should any part have been sufficiently exposed to the light, the paper will remain white, owing to the complete reduction of the ferric salt to the condition of the ferrous salt. It will be thus obvious that the Pellet process will therefore reproduce a positive as a positive, and a negative as a negative ; this circumstance giving it an especial value for copying tracings or drawings by direct contact printing. The paper for the Pellet method is supplied commercially by the patentees of the process ; but it is convenient for those who wish to practise it experimentally to be able to prepare their own ; and the following directions will be found amply sufficient. A solution is made of— Common salt ... ... ... 3 parts Perchloride of iron ... ... ... 8 ,, Tartaric acid ... ... ... 4 ,, in 100 parts of water ; and this mixture is thickened by stirring in 25 parts of powdered gum-arabic. The paper should be a well-sized and rolled paper, that known as cream laid note paper being the most suitable. It is easy to obtain this paper in the original sheets from a wholesale stationer. The sheet to be coated must be laid on a drawing-board, and it is desirable to fasten it down by means of two pins, after which the mixture is applied as evenly as possible with a broad camel’s hair brush. This operation should be performed in a subdued light, and it is desirable to dry the paper as quickly as practicable, in order that the sensitive coating may remain as much as possible upon the surface of the paper. When quite dry, the paper may be stored awny for future use. 1 he tracings from which copies are to be taken should n".Die.Modernen Lichtpaus Verfahren, rar herstellung cxicter Copien 'u teichnungen, Stichen, &c. ; Zweite Auflage, 85 Seiten ; 2 Mark, consist of well-defined opaque lines upon a ground ofclean tracing paper or tracing cloth, and many prefer to use Indian ink into which a little gamboge has been rubbed. It is unnecessary for us to say anything with respect to the kind of printing frames suitable for the process ; but it may be mentioned that large frames on swing stands are required in establishments where the cyanotype process is carried on commercially, as the drawings to be copied are often as much as four feet long. In sunlight an exposure of one or two minutes is gene rally sufficient, and in dull weather it may be necessary to give as long an exposure as one hour. Electric light is often used for work of this character, the time of exposure varying, according to the intensity of the light, from twenty minutes to half an-hour. To develop, the print is trans ferred direct from the copying frame to a saturated solution of ferrocyanide of potassium ; but it is not immersed in this, being merely floated upon it face downwards. In order to prevent the developing solution reaching the back of the paper, it is usual to told back the edges so that the paper forms a kind of dish, and this dish floats boat-fashion upon the developer. In ordinary cases, the development is com plete in less thana minute ; and as soon as the paper is once thoroughly wetted on the face, it may be lifted off the bath, as the solution adhering to the face will complete the deve lopment. A blue colouration of the ground indicates an insufficient exposure, while weakness of the lines indicates over-exposure. The development being complete, the print is floated, face downwards, upon clean water, and in about two minutes it is plunged into an acid bath containing 8 parts of hydrochloric acid and 3 parts of sulphuric acid, with 100 parts of water. From six to eight minutes is sufficient time to allow for the removal of redundant iron com pounds by the acid, and all that is now required is to thoroughly wash the print with water, and to dry it. Any blue spots may be readily removed from the finished print by means of a dilute solution of caustic potash, applied with a camel’s hair brush ; 1 part of potash dissolved in 28 parts of water answers the purpose admirably. When cyanotype prints are to he used in the workshop as a guide to working engineers, it is an excellent plan to saturate them with white hard varnish, as this prevents the penetration of oil and the adhesion of dirt. Other photographic tracing methods will be described in future articles. DISTORTION IN PORTRAITURE. In nine cases out of ten, where it is said that a portrait exhibits “ distortion,” it in reality does not do so, but merely shows the exaggerated perspective which is due to the use of a lens of too short focus, or, what is the same