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MARCH 16, 1883.] THE PHOTOGRAPHIC NEWS. 163 beat of a pendulum of some 39 inches is reckoned about one second. Our collodion plate has an exposure of two minutes, one of the yellow windows of the laboratory being lifted half way up to allow of the transparency or negative being illuminated. The developer contains three grains of iron to the ounce, and is used with a restrainer consisting of a little citric acid and alum. The development, therefore, is rather slow. No intensification follows, care being taken, indeed, not to get the half-tones too marked, as they otherwise get exaggerated in the after manipulations. Our thin collodion transparency has next the margins removed by simply passing the fingers round the plate, and scraping the collodion off. To loosen the film, it may be laid for a time in acidulated water (sulphuric acid four ounces, water one quart), for, as we have said, the glass receives no preparation to facilitate the separation of the film. It is now put into a dark brown solution of iodine, made by dissolving iodine crystals in iodide of potassium and water. The silver image is in this way converted into iodide of silver, and rapidly assumes a yellowish tinge. A few minutes only are necessary for the conversion—the film by this time is generally free of the glass, but this is kept underneath, as a convenient means of support—and then, after careful washing, it goes into the depositing bath. This last consists of iodine, bichloride of platinum, lead, and tin; and, according to Mr. Henderson, no better formula can be given than that mentioned in his specification. Here it is :— Bichloride of platinum 5 parts Bichloride of tin (or its compounds) 80 „ Iodine, to saturation Hydrochloric acid 960 „ Silicate of potash 20 „ Acetate of lead. 40 „ Water 8,000 „ It is necessary, while the film is in the platinum bath, that the solution should always be in motion, otherwise the deposition is not uniform. Mr. Henderson has an ordinary bottle-jack, from which is suspended a shelf, and upon this the platinum bath, containing the film, is placed. The shelf revolves, and thus the solution is never at rest. The film image now undergoes great change. It becomes dark and sooty in appearance. It appears so very much overdone and so opaque, that only firm faith in the process prevents you from throwing it away. The time required for depositing is rather undefined, for the process some times lasts for hours ; but it may be accomplished in a few minutes under favourable conditions, if the liquid is not cold ; and Mr. Henderson, in fact, is, at a pinch, cap able of getting through the whole process of enamelling, from taking the transparency down to firing the plate, in half-an-hour. We now come to the firing. Mr. Henderson uses a most serviceable little muffle furnace, constructed for him by Messrs. Nicole, Nielsen, and Co., of Soho Square, at a cost, we believe, of ten or twelve pounds. It is heated by Bunsen gas burners, so readily, that within twenty minutes after being lit, the inside is of a cherry red, and ready for use. In front of the furnace is a tray which serves to rest enamels upon, towarm them before entry into the furnace, or for withdrawing them for a moment, for examination, during the process of firing. An oval enamel plate is selected, polished with a little putty powder to free it from any traces of oxide, and then rubbed with an alkaline solution (caustic potash dissolved in water) to re move any grease or finger-marks. To avoid air-bubbles between film and enamel is of the greatest importance, and therefore the application of the one upon the other is done under water. The concave enamel plate is immersed side ways, so that it cannot act as a diving-bell, and retain air-bells underneath ; and then the sooty film, attached to the under side of a glass plate, is put under the water too, taking care that the film rests face upwards upon the enamel. In this, as, in fact, in every other manipulation in the process, practised skill is necessary, and hands new to the work are scarcely likely to perform perfect work at the first trial. The film being neatly and closely fitted over the enamel— a penknife is used for lifting the enamel, to avoid fingering—this is withdrawn from the water, and here the position of the image may be re-adjusted by skilful fingers ; indeed, very skilful fingers are necessary to adjust cleanly and nicely, for nowhere on the face of the image must there be 'a touch. The enamel is a very un promising thing to look at now : it is ten times as dark as it should be, and of a dirty opaque black. It is drained, and then put on the tray in front of the furnace to dry and warm. Gradually it turns to a brown, and loses much of its sooty blackness. In five minutes, or even less, it is brown all over, and ready for firing. Too rapid heating, however, induces blisters. Mr. Henderson has in his hand an iron spatula ; he opens the furnace door and takes out by means of this handy tool a porcelain plaque, of which there are several heating, and puts this hot biscuit-looking slab on the tray in front of the furnace. Then the spatula is slipped under the enamel and the latter put upon the plaque, where it gets rapidly heated. A few seconds elapse, and the enamel by this time being very hot, the spatula is slipped under it once more, and it is conveyed into the furnace. A pot of cold water close at hand serves to cool the spatula from time to time, and thus prevent an untoward accident to the manipulator. Gradually the image begins to assume a glaze at the edges. In two or three minutes the high lights are as shining as the enamel plate was before the image was placed upon jit, but the dark shadows still remain dull. Mr. Henderson puts his handy spatula under the enamel, and brings it out of his furnace for our inspection. It is of a lovely primrose colour, but the dark shadows in the hair are still dull; consequently it is remitted to the furnace for a few minutes longer, and now when it is withdrawn, although there is still the bright primrose tint, the whole surface is glossy in the extreme. The enamel is finished. It is permitted to cool, and the yellowness rapidly gives place to a brilliant white. The dark opaque brown shadows have all disappeared, and in their place are delicate and translucent half-tones and glossy blacks. In five minutes the enamel is perfectly cold, and Mr. Henderson presents it to us as a memento of our visit. But he quiekly takes it back again ; in the background are two minute black specks—dust that has dropped from the furnace. These are ruthlessly dug out with a penknife, retouched in fusible pigment by an assis tant, and the enamel once more committed to the oven. In two or three minutes the enamel has been again fused, and before long it is once more in our hands, without a sign of any imperfection. “Many think that/ success depends upon timing the sojourn of an enamel in the furnace to a second,” says Mr. Henderson ; and to show this is not the case, our friend selects a portrait by his side—it is one of a series of family pictures that Mr. Henderson is executing for the King of Siam—and, putting it into the furnace, shuts the door upon it for five minutes. At the end of this time, copper and enamel were so soft that the spatula could cut them in two, but still the image, except that its tint is slightly reddened by the operation, undergoes no change. “ No, the great enemy to enamel photography is dust, and therefore I take care to disturb it as little as possible,” says Mr. Henderson. Putty powder is a wonderful aid in enamel photography. Not only is it invaluable in polishing an enamel surface, but it permits you to modify your image. If this appears too dark, you may withdraw it from the furnace when only half fired, and when the more delicate tints are glazed, but the heavy shadows still unburnt. Then, a little fric tion with putty powder will reduce the darker shadows