Smith, of Bath, sent to me for enlargement, and he has kindly given me his formula, which works admirably, the only drawback being a slight liability to stain; the increase of power is obtained solely by change of color, and, as in the above, the solutions keep permanently.
1.- Persulphate of Uranium,................................
And, in a separate bottle,
2.- Ferrideyanide of Potassium,................................
Take a drachm (according to size of plate) of number one, and flood the plate whilst wet; pour back to the measure, and add number two, drop by drop, and work over the plate. It is the latter that gives the intensifying power, and it must be slowly added; the intensity is gradually given, and the result very beautiful. Which of these two systems is preferable I
189. After the negative has run the gauntlet of all the preceding troubles it must be varnished, as has already been stated. (See page 114.) It is then entrusted to the tender mercies of the printer, who, if in sympatic with the manipulator, will secure from it the best possible results. He is not always careful, however. The negative that produces the best results is the most used, and often the most abused. The varnish becomes full of dust and specks which are allowed to fall upon and become imbedded in it, and it must be removed and the plate revarnished. Or it may be that the negative is no longer serviceable, and it is required to remove the film in order to use the glass again.
really find it difficult to say, both are very good; and I fancy the composition of the image equally good in either case. Such negatives, when varnished, are as smooth as the glass itself. - Samuel Fry.
I read of a man whose health suffered from the use of intensifies. Why use mercury, 6ulphuret, etc., when iron will do the work quickly or slowly, as you choose to have it? Beside it works very effectually. Below is a formula for which I am indebted to the editor of the Philadelphia Photographer; since using it I have had no trouble in getting all the intensity I want. If it turns muddy, increase the dose of the acid a little. Here it is:
Sulphate of Iron,............................
Use either before or after faxing, as you like best, with a few drops of silver in it just before use, as in case of the pyro. intensifier. - Ranald Douglass.
189. Many methods have been suggested for removing the varnish from old plates. A mixture of benzine and alcohol in equal parts, agitated and poured on the plate, generally acts very quickly and very well. The last traces of reduced silver which may yet adhere are then removed by iodized alcohol (alcohol 100, iodine 0.50). When the surface is properly cleaned, it is rubbed over with the finger or a tuft of cotton lightly impregnated with tallow, and wiped dry. Plates thus prepared may be kept indefinitely, and are protected from dampness, the enemy which too often imposes itself between the collodion and its support. - Elbert Anderson.
Fill a large, flat, and deep porcelain dish with as many old negatives as it will hold, or that yon may wish to destroy, so overlapping their edges or placing them that there will be small space between the surface of each of the plates. Then pour upon the entire batch sufficient commercial nitric acid to entirely cover it. Add about four ounces of strong alcohol to each quart of the acid. No action takes place immediately; but in about ten minutes ebullition commences, and dense noxious fumes will be violently emitted. In an incredibly short time collodion skins, protected by the hardest and most impenetrable varnish, will entirely leave the glasses, and they are ready for a slight washing, albumenizing, and further use. It is scarcely necessary to suggest that the dish should be placed in the strong draught of a chimney, or in the open air. In half an hour you can more simply and effectually cleanse more old negatives than by days of treatment with alkalies and acids used in any other manner. - John L. Gihon.
Cover the bottom of a dish with the negatives, face upwards; pour oil of vitriol (sulphuric acid) on the top of one, in quantity equal in size to a half - crown. Then place another negative, face down, on the acid. It will soon spread itself all over between the negatives if sufficient is added, and the dish level. Now do the same to all the other glasses lying on the bottom; after which, another layer, face upwards, and another, face downwards, with acid, of course, between them. The varnish is removed almost instantly, and the plate left chemically clean. When the dish is full, tip it up, and pour off the excess of acid into Mother bottle until it ceases to run in a stream, but not longer. The acid is now black with the charcoal from the decomposed organic matter on the plate. This used acid is the first to be employed on the next occasion, but requires a little more to be used, and allowed to rest an hour or two after the excess has been poured off as before directed. The next thing to do is to upset the dish in a pan of water, separate the glasses, and rub their surfaces with the hand under water, and then let a little stream of clean water play on both surfaces for half a minute, and stand up to drain. There is no danger of the acid injuring the fingers under water, nor is it liable to splash when being poured on the plates - it is too oily fur that. This acid is far more rapid than nitric acid, gives off no corrosive fumes, and is very cheap. The bottle ought to have a stream of water played over it before put aside, so as to be clean and dry for the next occasion. I never get a dirty plate by this means.- - T.S.Reeves.
190. Another sort of carelessness also causes trouble with the varied plates. If they are kept in a damp place the film will rise up and form inequalities, which, when pressed upon, burst, and the plate is rained - checkered hopelessly to all appearance, Again, rents oocur in the film, resulting from dirty plates as well as dampness. Often a valuable negative brought out from the rack, where it has been stored for some time, looking pitiful enough. Sometimes racking it away in a cold place, while it is still hot from printing in the sun, will cause such defects.