THE PHOTOGRAPHIC NEWS.
Vol. III., No. 70.--January, 6, 1860.
IT would appear that many of your correspondents who have used the printing process detailed by "Theta" (vol. ii. p.16) regard him as the author of it. This, however, is not the case, nor does" Theta" himself lay any claim to the invention. Indeed, the whole process, with the exception of the toning bath, was published in 1854, by Mr. Sutton, of Jersey, and it may be found in both editions of his work on the calotype process, the first of which bears the date of March, 1855. it is well known that Mr. Sutton is the author of the sel d'or toning process--a vast improvement on the processes which were in use prior to its publication; but, as albumenised paper had then been recently invented, it became the rage, and sel d'or (which was adapted for plain paper only) was given up for a hypo. bath, to which acid chloride of gold was added. and in which albumenised paper could be toned. Most of the prints toned in this way have faded, while those toned by the sel d'or process have generally stood well, and retained their freshness. The author of toning by chloride of gold and hydrochloric acid was M. Le Gray, of Paris. The hydrochloric acid was, after some experience, omitted, its effects being injurious to the permanency of the prints, which soon exhibited unmistakable signs of fading. The usual terchloride was then employed, but still acid with excess of hydrochloric acid, in conjunction with a bath of hyposulphite of soda. Many modifications of this mode of toning have been published, but, owing to a cause no one could find out or explain, the process was far from satisfactory. At length it occurred to some one to neutralise the hydrochloric acid in the terchloride of gold, and make an alkaline instead of an acid toning bath. The idea was put into practice, and succeeded beyond expectation. Who it was first hit on this notion not certainly known, but it seems it had been in private use for two or three years before the public knew anything about it, and I understand that Mr. Francis, of Great Russell Street, London, claims the invention. --If so, it is a pity he did not publish his discovery. It appears also that Mr. Waterhouse, of Halifax, was an independent discoverer of the advantages of employing an alkaline instead of an acid gold bath. He, too, kept the matter a secret, until the printing committee of the Photographic Society was appointed, when he forwarded to the committee some prints to be tested, and, at the same time, communicated his method of toning them. "Finding (said he) that Le Gray's process eats into the picture, I modify it by using an alkaline instead of an acid solution of gold. The alkali I employ is the potassae subcarb., and I add more or less of it, according to the tint desired." Mr. Hardwich suggested the use of carbonate of soda instead of carbonate of potash, not because it is better, but for the reason that it is more easily obtainable; and at the meeting of the London Photographic Society, in December, 1858, he read a paper on "Toning by Alkaline Chloride of Gold," expressly stating that- it was founded on Mr. Waterhouse's modification--the value and importance of which he fully recognized. -
In February last, Mr. Maxwell Lyte sent to the French Photographic Society an account of a new gold-toning process which he had adopted, and which will be found at p.301 of the first volume of the "PHOTOGRAPHIC NEWS." Mr. Sutton has, since that time, published a printing process for albumenised paper, containing some important modifications. As all these systems proceed on precisely the same principles, which are now admitted to be the only correct ones, I have taken the trouble to compare and consolidate them for my own use, and I now forward them to you for publication, should you think them likely to be acceptable to your readers.
1. To Albumenise the Paper.--Beat up to a stiff froth equal parts of white of egg and water, containing 15 grains of salt and 1 minim glacial acetic acid to each ounce. When sufficiently settled, filter into a flat dish. Float plain paper on this for half a minute, and hang up to dry quickly in a warm room. If less salt than the above is used, the prints are liable to turn red in the hype. fixing bath.
2. To Sensitive the Paper.--This is usually done by floating it on a 60 grain bath of crystallised nitrate of silver. Mr. Melhuish, in his paper on this subject- (supra, p. 153), recommends a. bath of 75 grains, and Mr. Sutton has expressed his entire approval of this change, as it produces more brilliant prints. Float the paper for two minutes only on the stronger bath, taking care that the solution does not sink into the paper. if it does, remove it immediately. If floated too long, a dull print will be the certain result: therefore excite quickly, and dry quickly.--N.B. It has been recommended to add one drop of nitric acid to every drachm of sensitising bath, and it is said that this addition will preserve the paper without discoloration for six weeks after sensitising. Should this not be adopted, it will be advisable to add one grain of citric acid to each ounce of bath, to insure red and brilliant prints. -
3. The Exposure.--Print rather deep. On taking the proof from the frame, it should look vigorous and clean, or no toiling process will make it so; neither can a vigorous print be obtained from a feeble negative. The proof must-not be exposed to daylight, and the subsequent operations must be conducted in the dark room, or by yellow light only.
4. To Wash the Free Nitrate of Silver from the Proof.-- Place it in a fiat dish containing a small quantity of water, just enough to cover the print, and let it remain five minutes or longer Then pour off the water into a jug, and pour it from the jug over the surface of the print-. Repeat this six or eight times ; then throw the water into a large pan containing salt, which will in a few hours precipitate the silver in the form of insoluble white chloride of tint metal By this treatment, 95 per cent. of the silver in the print may be- saved. The print must now be finally washed well under a tap, and, if all the free nitrate be thus removed, may be -at once immersed in the gold bath. If, however, free nitrate be left on the print, it will injure the gold bath by throwing down chloride of silver and metallic gold. To prevent this, Mr. Sutton formerly prescribed immersion in a bath of water containing a few drops of ammonia. He does not now advise this course. The simplest form is to use a bath of salt and water, containing a quarter of an ounce of salt to the pint. Leave the proof in this for 8 to 5 minutes, and it may then be transferred to the gold bath without washing.
5. The Gold-toning Bath.--This bath consists of 1 drachm of a solution of auro-chloride of sodium in 4 ounces of clean filtered water. This quantity will tone a whole sheet of Canson's or Marion's paper, or even more. If, however, 4 ounces will tone 16 stereo. prints, each print will require 2 drachms of the bath. No more solution must- be used than is actually necessary for the print or prints to be toned. If it be wished to tone only one stereo. print, pour 2 drachms into the flat dish, and add 2 drachms water, to cover the paper. The quantity used for one print may be used for another. If it becomes turbid, filter it; but when the gold in it is exhausted, throw it away, and use fresh. On no account must fresh chloride of gold be added to strengthen the solution that has been used, as by so doing the subsequent proofs immersed in it become intensely yellow, and consequently worthless.
The auro-chloride of sodium solution is made by dissolving 15 grains of chloride of -gold in 10 drachms of water, and then adding 15 grains bicarbonate of soda; dissolved in 5 drachms distilled water. Do not exceed this quantity of carbonate of soda, or the excess -will act injuriously on the organic part of the silver image, and also loosen or dissolve the size in the paper. Phosphate of soda is not open to this objection, and may therefore be added to the bath, at the rate of 15 or 20 grains phosphate to every grams of auro-chloride of sodium, i.e., to every 4 ounces of bath. -
The proof, on immersion in the toning bath, quickly assumes the Purple hue conferred by gold, and must be removed before it becomes black, and while there is a tinge of redness in it, as it afterwards does not look so red as when in the bath. About a minute will be generally long enough when the solution is fresh.
On removal from the bath, wash the print well in several changes of water before placing it in the hypo. This is important, and should not be neglected.
6. To Fix the Print.--This is done by immersion in a solution of hyposulphite of soda, 3 ounces to the pint of water. Test the solution for acidity, and neutralise it by adding a small quantity of chalk, or carbonate of lime, but not carbonate of soda. Although the hypo. baths must not be acid, neither must it be too decidedly alkaline, or it will injure the purple tone conferred by the gold. English papers are more liable than foreign ones to become red in the fixing bath. When the print has been in the hypo. 10 or 15 minutes, hold it up to the light, and, if it be transparent all over, the chloride of silver is dissolved out of the papers If not, put it back again, till the opaque parts have become transparent ; then remove it, and wash it under a tap for several minutes, after which, place it in running water for three or four hours. Or, to expedite the process, adopt the method of Mr. Warwick (vol. i., p.227), or that recommended at p.71 of vol. ii.. both of which may be combined with advantage. After undergoing this or the usual treatment, the print is dried and mounted.
It must be added that the hypo. used for one printing should not be employed for a second, and that it will be advisable to put aside a bath after a dozen prints have been fixed in it, and use fresh solution for any remaining prints that are to be fixed. This being the case, no greater quantity should be used at a time than is necessary to cover the prints which are immersed in it.
The preceding mode of printing is not only in every respect superior to that employed by "Theta," but shows that his toning-bath, containing from 20-30 grains of carbonate of soda to each grain of chloride of gold, is wrong in principle and injurious in practice, and ought, therefore, to be given up. Those who employ the process here given, manipulating carefully, and doing the various washings efficiently, may calculate on brilliant prints of first-rate quality, the permanency of which may be confidently predicted.R.