THE PHOTOGRAPHIC NEWS, Vol. IV., No. 117, November 30, 1860.
The method of toning silver prints by means of a solution of alkaline chloride of gold has now been before the public for two years, and has, we think, fully justified the hopes which have been entertained from its first introduction regarding its value as a toning agent for permanent prints. The "old hypo" bath is gradually- becoming discarded, except in some commercial establishments where economy is considered more important than the production of permanent photographs.
It must not be overlooked, however, that notwithstanding the success which has attended its use in the main, failures and disappointments in its application have occurred in many instances. A curious illustration has been afforded of a law which seems to pervade the world of physics as well as of ethics; namely, that in proportion to the perfectness of a tart must be the perfectness of the whole, in order to obtain harmonious results. That in order to secure the success of a perfect theory, we must have perfect application of that theory. In using the alkaline gold toning baths we must, if we would attain a satisfactory print, have everything in its best condition, and the manipulations must be conducted with the utmost care throughout.
The negative should be perfect, brilliant, and vigorous, with a few points of perfect opacity for the highest lights, delicately graduating to a few points of perfect transparency for the deepest shadows. Mr. O.G. Rejlander recently remarked, in a conversation we had with him on thus subject, that for producing a perfect print from a perfect negative, tendering with the utmost truth and faithfulness every beauty in the negative, he knew of no process which could equal the process of printing, toning, and fixing recommended by Mr. Maxwell Lyte.
The paper should be good, and selected with a special view to the kind of result desired. If delicate gradations of black or grey tones are desired, then Saxe paper will generally be found to answer. If bold contrasts and reddish tones are desired, a thicker paper more highly albumenized should be used: seine of the English papers, and the papier Rice will be found to meet the latter requirement.
The preparation of the paper by salting and albumenizing should be conducted with an especial view to the use of the alkaline gold toning bath. A maximum proportion of salt should be added to the albumen--Maxwell Lyte recommends as much as four per cent., which is about nineteen grains to the ounce. About fifteen grains to the ounce we have found to give good results. In many establishments where paper is albumenized in a wholesale manner, about ten or twelve grains are used, and in some we have heard that it is added by guess. It will be a fortunate thing for photographers when albumenizers of paper can be induced to state the strength of the salting solutions used in the preparation of various samples of paper, so that they may know exactly with what they are working. The albumenizing should be so conducted as to keep it well on the surface of the paper, instead of sinking into its texture. Short floating and rapid drying materially- tend to this result.
The silver: solution should h)e made strong enough, and the strength well kept up. Sixty- grains of nitrate of silver are generally regarded as a normal strength; if, however, nineteen grains of salt be used, as recommended by Mr. Lyte, the silver solution should 'be much stronger, say about one hundred grains to the ounce of water. If fifteen grains of salt be used, a silver bath of about seventy or seventy-five grains to the ounce will be desirable. A bath of sixty grains will be sufficiently strong for most commercial samples of albumenized paper, as they do not generally contain a larger proportion of salt than twelve grains to the ounce. In all oases, a strong bath, short floating and quick drying, gives the most brilliant prints. It is of the utmost importance that the silver bath should be from time to time tested and the strength of it kept up.
The printing should be effected as soon after exciting the paper as possible. Considerable over-printing is generally desirable; the lights should be of a delicate lavender tint, and the shadows deeply bronzed before the print leaves the pressure frame.
The prints should be washed in two or three changes of water just before toning, and the final washing water may have a little salt added. Long soaking in salt and water renders the toning more difficult. All the processes in connection with printing and toning, with the exception of exposure, should be conducted in the dark or in yellow light, and the most scrupulous cleanliness as to the fingers and dishes be observed. In regard to the latter, it is desirable that each one be kept to its own purpose and never used for any other; and the utmost care should be taken not to put the fingers into the gold solution which have just touched the hyposulphite of soda.
Several different forms of the alkaline gold toning bath have been proposed, all of which have been practised with more or less of success. We shall only refer to those with the results of which we are familiar, and can speak with personal confidence. The first is the process of Mr. Maxwell Lyte, with which most photographers are already familiar. It stands thus :--
Chloride of gold
|Phosphate of soda||18 grains|
|Distilled water, quantum suff.|
The chloride of gold and phosphate of soda should each be kept in solutions of given strength, say one grain of gold to an ounce of water, and eighteen grains of phosphate of soda to an ounce of water; they can be then well mixed in any quantity required for use, and diluted with sufficient water to float the prints in easily. The only effect of using a large quantity of water is to make the process of toning somewhat slower, which is frequently an advantage. Sufficient water tends moreover to secure regular toning. The prints should be kept moving, and prevented from sticking together, or red, imperfectly-toned patches will be the result. The water used for diluting the bath may be previously made warm, as it materially facilitates the process, especially in cold weather.
The process of toning is more rapid in some cases than others, but in most cases a few minutes--from about two minutes to ten--is sufficient. It is in all cases desirable to allow the print to assume a little deeper tint than is desired in the finished picture, as a little will be lost in the hypo fixing bath. If a sepia or purple brown be required, a decided purple tint should be obtained in the toning bath, If a decided purple lie desired, then the tint in the toning bath should be black,
For the phosphate of soda, the bicarbonate of soda, or biborate of soda, may be substituted, but in less proportions--in regard to the carbonate, especially as an excess of it has a tendency to dissolve the size of the print, and in some cases even the albumen. Five grains will, therefore, be generally found sufficient, the only object being to neutralize the free acid in the chloride of gold.
We have seen very fine prints produced by the toning process recommended by Legray, which is as follows:--
Chloride of gold
|Chloride of lime||1 "|
|Chloride of sodium||1 "|
|Distilled water||4 ounces.|
The treatment is similar to the first mentioned, but as it has a strong bleaching tendency, it is necessary that the prints be considerably over-printed.
The last process of gold toning to which we shall refer is one published during the past year as being the suggestion of M. l'Abbé Laborde. We may mention, however, that its advantage had been pointed out some months before by Mr. Hannaford, who states that a peculiarly rich purple bloom is secured, which is absent when any other salt of soda is used with the gold, with the exception of the citrate as proposed by Mr. Hardwich, which has a similar effect. Mr. Hannaford states that it has another advantage, which the Abbé confirms; namely, that it may be used more than once; all other toning baths being useless for toning purposes after once being used for toning. The formula stands as follows:--
Chloride of gold
|Acetate of soda||7½ drachms|
The solution becomes colourless by degrees, and at the expiration of twenty-four hours it is ready for use. On removing the positive from the printing frame it is washed in two or three waters, to remove the free nitrate of silver; it is then immersed in the gold bath, where it must be allowed to remain not more than twenty-five to thirty seconds, when the bath is first used.
If the gold bath has been used before, its action is slower. Experience will enable the operator to see by the successive changes in tone the proof assumes when he should remove it from the bath. If it be removed too soon, the proof assumes a disagreeable red hue after it is fixed with the hypo; on the other hand, if it be allowed to remain too long in the gold bath, the proof assumes a cold blue tint. Between these two extremes there are a variety of tones of sepia and of violet, which can be secured by removing the proof at the proper moment. In proportion to the length of time the gold bath has been used, so we must prolong the toning, until the required tint appears. The strength of the gold bath can be restored by adding fresh chloride of gold; but before making the addition, we must take care that the solution is nearly colourless, for if the chloride of gold is not in combination, it will, like other chlorides, weaken the proof.
In all cases the prints should be washed in two or three changes of water, and then immersed in the hyposulphate of soda, which it is desirable should possess a strength of at least twenty per cent., or four ounces to a pint of water. It is better used fresh each time, and should be neutral or slightly alkaline. Mr. Lyte recommends the addition of a little Spanish white, or chalk, for the purpose. Prints on thin paper are more rapidly fixed than those on thick; but they should not in any case be removed from the fixing bath in a shorter time than ten minutes. They should then be washed in several plentiful changes of water within the first half-hour; and subsequently soaked and washed so as to thoroughly remove all traces of hyposulphite of soda.--Photographic News Almanac.