Sunday, September 7, 2008

EX CATHEDRA: Liver Toning; Rapid Plates and Donalty; Carbon Printing and Fumes; Simper Paratus; For Print-Out Papers.

Liver Toning.

There seems to be in some quarters a difficulty in getting satisfactory tones on bromide prints with the ordinary sulphide toning process. Instead of obtaining good rich sepia tones a rusty colour is got, due sometimes to a want of density in the negatives, or to over-exposure followed by insufficient development, while in other cases no modification in working will give the desired colour. To those who find themselves troubled in this way we recommend a trial of liver of sulphur (potassa sulphurata) as a toning agent. This has the advantage of giving a variety of colour, ranging from a warm black to sepia, including some very fine purple browns. One of its good points is an absence of the slight reducing tendency of the ferri cyanide bleacher, and another is that even if the prints are inclined to be weak there is no liability to give a "ginger" colour. The process is a simple one; the toning bath consists only of sixty grains of "liver" to a pint of warm water, a few drops of ammonia being added when solution is complete. This should be raised to a temperature of about 100 deg. Fahr, and the print immersed until the desired colour is reached. A little allowance must be made for the further toning action, which goes on in the subsequent washing. Borne papers will stand the heat of the solution without requiring hardening, but if there is any tendency to melt the prints should receive a preliminary bath of formalin, a convenient strength being two ounces to the pint. As with the hypo-alum bath, all papers will not tone to sepia in the liver of sulphur solution, some is refusing to go beyond a purple black similar to P.O. P. A few trials with various papers will show the most suitable makes.

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Rapid Plates and Donalty.

It is commonly believed that it is difficult to obtain full density when using very
rapid plates and some operators prefer to use a slower grade in order to secure plucky negatives. The idea is fostered by the fact that the films of nearly all fast plates appear much more transparent before development than do those of slower ones, and this gives rise to the belief that such plates are thinly coated and lacking in silver. Such is certainly not the case; the fast plates having in some cases twice as much silver bromide spread over the square inch u the "ordinary" ones. We have used plates which were so transparent that ordinary printing could easily be read through the emulsion, but which gave almost perfect opacity when developed. The fact is that much longer development is necessary for a fast emulsion than for a slow one. If we take two plates of the san e make, one an ordinary and the other a "supersensitive" expose both correctly and develop in the same developer for the same length of lime, the difference will be most marked, but if the rapid plate be developed twice or even three times a long the densities will then be pretty even. Instead of prolonging the development the Mine effect may be produced by increasing the amount of alkali, or by raising the temperature of the developer. With regard to the former expedient, a little mishap which recently occurred to us will be instructive. By mistake carbonate of soda was used instead of sulphite in making a stock pyro solution, and by so doing the amount of alkali in the mixed developer was more than doubled. Upon developing for the usual time plates which normally gave thin delicate images became so dense that considerable reduction was necessary before the negatives were printable, a conclusive proof that a full quantity of silver was present.

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Carbon Printing and Fumes

In some unaccountable way the notion, has been created that carbon tissue is extremely sensitive to various fumes, and many have been deterred "from using this charming process because they thought that special precautions had to be taken to avoid "tinting," or what would be called "fog" in other processes. We have recently seen excellent carbon prints, which were produced day after day under conditions which are popularly believed to be impossible. They were made in a work-room in which an evil-smelling dry mounting press was used almost constantly; by the side of the sink a geyser was used to supply the hot water needed, and three feet away the sulphide of bromide prints was constantly done. The reason for the immunity from the ill effects of this combination was a simple one; only ready-sensitized tissue was used. In a dry state the fumes had practically no effect upon it, and the short time it was exposed while wet during the mounting did not allow any action either. The great stumbling-block in carbon work is the drying when home-sensitized tissue is used, and practically all risk of "tint" may be avoided by drying the tissue in an air-tight box or cupboard over chloride of calcium. By so doing, not only is the atmosphere excluded, but the drying is done in the same time whatever the hygroscopic conditions may be outside. Another advantage gained by this method of drying is that the tissue is of uniform sensitiveness, which is not the case when it is dried in the open.

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Simper Paratus

There is an old joke which is sometimes trotted out when anything uncommon presents itself "that you always see these things when you have not got your gun." If for gun we substitute camera we are recording the experience of nearly every photographer. Most of us can recall many occasions when we have seen effects of light and shade, or occurrences, which are not likely to be repeated, and have been compelled to leave them unrecorded because our camera was out of reach. We have known some photographers, mostly enthusiastic amateurs, who never went out without a camera, and at least one professional who did the same, told us that, on the whole, the practice had been a profitable one, besides being the means of securing many pictures of personal interest. This was in the days when the smallest camera was of the dimensions of a cigar box, and it required much more enthusiasm than in these times of pocket Kodak’s and "baby" plate cameras. Apart from the constant carrying of a camera, it is an excellent to keep a small instrument, say, half-plate or less, ready filled with plates or films which can be picked up and used without a moment's delay. In this respect the amateur with his film outfit is usually much better prepared than his professional brother, who often has to assemble his outfit before it is ready for use. Perhaps the most convenient apparatus is of the folding local plane or "press" type, in which plates can be kept for weeks without danger of deterioration. Such a camera is of great value for sports, pictures, street scenes, and the like, while used with discretion it is very handy for home portraiture. The great point is that it should be semper paratus, always prepared.

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For Print-Out Papers.

The consistent reader of the photographic papers is constantly coming upon hints so ancient that, like the anecdotes of Miss Volumnia Deadlock, they have become in the cycles of time new again. At least forty years ago photographers who had need to make a very dense part of a negative impress its detail fully on the print would use for the purpose the concentrated light of a burning-glass. This old expedient must have been disinterred scores of times or, quite possibly, has been invented by those who have heralded it as a new device. Its latest appearance as something original is in a recent issue of a New York photographic paper. None the less, it is a plan which may often be employed with advantage in the case of negatives of interior subjects in which most probably windows or other brightly lighted parts have become too dense in the developer. In place- of risking the negative by reducing or rubbing down the more opaque parts, an ordinary reading-glass of about three inches diameter may be held in front of the negative during printing and, while kept gently in motion, caused to concentrate its light upon the part which needs help. The American writer prefers to fit a disc of black card with a hole in it in the rim of the glass and so to obtain the utmost concentration of light.

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