The Barnet Book of Photography Part 15

7. The following bath claims to have the advantage that it will keep in working order for a short time at any rate, but the disadvantage that it cannot be used until it has been mixed twelve to twenty-four hours.

Soda acetate 60 grains.

Ammonium sulphocyanide 20 "

Gold chloride 1 grain.

Water 12 ounces.

Toning should be conducted in very weak daylight, or what is much better, gas or lamplight. The latter, being practically constant, enables the operator to judge the relative colour of the prints from time to time. Care must be taken so that the prints do not stick together in the toning bath, and preferably only a few, say half-a-dozen or so, dealt with at a time, so that each print can be frequently turned over and examined. The change of colours proceeds somewhat slowly at first, but when once it begins it seems to gain in rapidity of rate of change, so that a careful watch must be kept.

Let it be remembered that the print, after fixing and drying, will appear a little darker and more blue (less red) than when wet in the toning bath. The temperature of the bath must not be too cold or toning is very slow, nor too warm or the gelatine may melt and toning be uneven. From 60 to 65 F. will be found a convenient range. The prints should not be touched on their printed surface more than can be helped. The fingers must be quite clean, the solutions uncontaminated with other chemicals, and a dish set apart for toning operations only. This dish should always be washed out well with tepid or cold water before and after use, and when put away should rest flat, opening downwards, on a shelf covered with a sheet of clean blotting paper. Many failures in toning are entirely due to lack of care in details and sufficient attention to cleanliness.

When toning is judged to be carried far enough, the prints should be placed in a roomy dish containing a solution of common salt, strength one ounce to twenty or thirty ounces of water, to stop further toning.

Fixing is done with a "one in ten" solution of sodium thiosulphite--_i.e._, hypo. This should be prepared with tepid water, or some time before use, as the dissolving of hypo in water is accompanied by a fall of temperature. A convenient method is to place a couple of ounces of hypo in a clean pint jug, and add about half a pint of fairly warm water and stir with a gla.s.s rod until the salt is dissolved, then fill up the jug from the tap with cold water. It is highly desirable to have plenty of fixing solution, and never attempt to use the same lot twice. Place each print face down in the bath and submerge by pressing on its back. Again see that the prints do not stick to each other, and turn each print two or three times. They should be in the fixing bath not less than twelve or fifteen minutes, and a few minutes longer will do no harm. At the end of, say, fifteen minutes, pour away about one half of the fixing bath and slowly fill up with water. Turn the prints again, and then transfer them one by one to another roomy dish and wash in running water for a couple of hours, or in a dozen changes of water every five or ten minutes. Then hang up to dry, using either clips or pin a corner to the edge of a wooden shelf or long lath suspended in a cool, airy place.

_Alum Bath._--Hot weather considerably increases the danger of the gelatine melting. To meet this trouble the following plan has to be resorted to:--

8. Dissolve common (potash) alum, one ounce in a pint of tepid water. Let it stand until cold and pour off gently the clear part should any sediment appear. After washing and before toning, place the prints in this alum bath for about ten minutes and _again_ wash before toning for ten or fifteen minutes in running water.

_The Combined (Toning and Fixing) Bath._--The general weight of opinion is _not_ in favour of combining these two operations at one time when reliable results are desired. Nevertheless, there are times when this method may be found a convenience and yield results which are all that may be desired. The following bath is a favourite with some workers:--

9. Ammonium sulphocyanide 15 grains Table salt 30 grains Hypo 2 ounces Water 10 ounces

To this is _slowly_ added one grain of gold chloride in half an ounce of water. The prints first washed for five or ten minutes in running water, and placed in the combined bath and kept moving by being constantly turned over and over for about ten or fifteen minutes. The longer they remain in the bath the more blue and less red will they be when dried.

Here is another bath which finds some stout supporters:--

10. Ammonium sulphocyanide 20 grains Hypo 1 ounce Alum 30 grains Water 10 ounces

Shake well, until thoroughly dissolved, then add

Lead nitrate 20 grains

Again shake well and set aside to settle, pour off the clear part, and add

Gold chloride 1 grain

dissolved in half an ounce of water.

Others recommend a still more simple bath as follows:--

11. Hypo 1 ounce Water 8 ounces Gold chloride 1 grain

It is said that this bath gives better results if it is prepared a few hours before use, _e.g._, prepared in the morning and used in the evening. Meanwhile, it should be kept away from daylight, and not in a very cold place.

_Drying and Glazing._--Some workers are of opinion that it is better to first "rough dry" the prints, _e.g._, by suspending by clips, or pinning one corner to a strip of wood, etc., and then to wet again and dry on a rough or smooth surface according as a matt or glazed final effect is desired. If however, the print has been through the alum bath (No. 8.) this preliminary rough drying may not be necessary.

_Matt Surface._--The matt paper when rough dried has a matt or slightly rough surface, but it may be desired to accentuate the effect. This may be done as follows:--Thoroughly clean with soap water and a nail brush a sheet of "fine-ground" gla.s.s similar to that used for a focussing screen. When quite dry, lightly dust it with fine talc powder (French chalk) and polish off again with a bit of clean rag. Now slip this plate rough side up into a dish of cold water, which also contains the print face downwards. Bring the print and gla.s.s into contact under water, carefully avoiding any air bubbles between them, as the two together are now raised from the water; firmly, evenly, but lightly pa.s.s a squeegee over the back of the print now in contact with the gla.s.s. Then lightly press a sheet of blotting paper over the print to take up all adhering water, and set up in a cool airy place to dry, _e.g._, in a pa.s.sage or between the door and half-open window. When quite dry, the print will very probably of itself come away from the gla.s.s, but if not, the finger nail inserted under one corner and a gently backward pull will separate it from the gla.s.s. In place of the fine ground gla.s.s, rougher gla.s.s of course may be employed. Some workers also use for the same purpose a sheet of roughened celluloid. This is more costly than gla.s.s, but being not so fragile may prove cheaper in the end.

_Glazing Prints_ is done exactly in the same way, with the single difference, of course, that we use a _smooth_ piece of gla.s.s, vulcanite, celluloid, paper mache slab, sheet of ferrotype metal, etc., etc., in place of a ground-matt, or rough surface. All the above-named substances have their partizans; perhaps the greatest favourite being good plate gla.s.s free from scratches. In all cases it is important to attend to two points, _viz._, thoroughly cleaning the support and waxing it. Various substances and mixtures have been recommended for giving a glaze, polish to the gla.s.s, etc. Many workers adhere to the powdered talc or French chalk already mentioned. Others prefer some of the mixtures given below:--

12. Bees wax 20 grains Turpentine 1 ounce

13. Spermaceti 20 grains Benzole 1 ounce

A few drops only of the lubricant are applied to the gla.s.s plate with a bit of clean flannel, and well rubbed all over. Then a final polish is given with a clean old silk handkerchief, or clean dry wash leather. On no account attempt to strip the print from the gla.s.s until the print is _quite_ dry or failure is more than likely to arise.

_Mounting._--Care should be taken that the mountant does not give an acid reaction. Test with litmus paper. Clearly it is no use being at the trouble of producing a high gloss on the print if we are going to damp the print and so destroy the gloss in the operation of mounting. To avoid this, various plans have been adopted.

(1.) If a cut-out mount is used it will suffice if the print be attached to the mount by glue at the edges only of the "cut-out."

(2.) Another method is to paste down on to the back of the print before it is quite dry, and while still on the glazing support, a backing of thin waterproof paper specially prepared for this purpose. This prevents the moisture of the mountant penetrating to the print. (3.) Another plan is to use a mountant which does not contain water. The following mixtures are recommended:--

14. Masticated rubber 10 grains Benzole 1 ounce

A thin layer of this is applied by means of a short, stiff, flat hog's hair brush to the back of the print. It is then allowed to evaporate for a minute or so, and when tacky is applied to the mount, covered with a sheet of glazed paper, and a roller squeegee pa.s.sed over the surface.

15. Saturated solution of bleached sh.e.l.lac in alcohol.

This must be applied as thinly as possible.

16. Le Page's fish glue applied to the edges only of the back of the print.

A fourth method is to first carefully clean the edges of the gla.s.s surrounding the print still adhering to it. Then to paste down the mount to the print and let all dry. Then strip the print from the gla.s.s now already mounted. This is, however, a process not to be recommended, because requiring a long time for the print to dry, as the evaporation has to take place through the substance of the mount.

ADDITIONAL PROCEDURES WITH P.O.P.

_Development of Partially Printed Proofs._--This method of procedure is sometimes a matter of convenience in dull weather, etc. The printing is to be carried on until one can just see a very slight indication of detail in the high-lights. It is then washed in running water for about ten minutes, and then put into a ten per cent. bath of pota.s.sium bromide, and there it remains for another ten minutes or so. In this bath some of the image seems to fade away, and generally the print takes on a yellow tinge. The print is next washed in running water for about ten minutes, and then developed with ortol, metol, or preferably, hydroquinone. A considerable variation in the proportions of the const.i.tuents of the developer are possible. In general terms, one may say that a developer which gives a good black and white lantern slide when diluted with about an equal quant.i.ty of water will give a satisfactory print.

17. As an example of a thoroughly practical developer for this purpose we may give just one example:--

A Hydroquinone 70 grains Pota.s.sium metabisulphite 5 "

Pota.s.sium bromide 30 "

Water 20 ounces

B Soda sulphite 1 ounce Caustic soda 60 grains Water 20 ounces

Take equal parts and mix just before use, wash for at least ten minutes in running water at once after development.

Developed prints may be toned in the combined bath 9, 10 or 11, or may first be fixed, then _thoroughly_ washed, and then toned and again washed.

If good results are wanted by the development process it is important to be careful that the paper is not exposed even to weak daylight more than can be helped, and not even to strong artificial light more than is necessary. At the same time it is quite practicable to do the operation of the bromide bath and developing in fairly strong gaslight, _i.e._, one need by no means be limited to the ordinary dark-room light as when developing plates.

Another point worth noting is that it is quite practicable to use magnesium ribbon for printing. For a rather thin negative it will be perhaps found sufficient to burn about a foot of the metal ribbon about three or four inches from the gla.s.s. The printing frame should be set up on edge in the vertical plane. The strip of metal ribbon is held by a pair of pliers, and ignited at the flame of a candle or spirit lamp. The lid of a biscuit box just in front of the frame does very well to catch the white magnesium oxide formed by burning.

It is as well to move the flame of the burning metal opposite various parts of the negative during the exposure. It will be found a comfort to wear a pair of rather dark blue gla.s.ses during this operation, as the bright light of combustion prevents one seeing anything with ease for a little while.

After development the print may be fixed only, and under certain conditions it is possible to obtain a fairly satisfactory black or brown colour without toning, but there is usually a slight tendency towards rather too much yellow.

_Platinum Toning._--This method of toning is a favourite with many workers. By it a considerable variety of colour tones may be obtained, from a rich red chocolate brown through sepia brown to a warm black.