Chapter VIII: Part 8

_Metol Developer._--With this, and the other developers I shall mention, an acid bath is not necessary and so one cause of failure (and extra work) is obviated. I have somewhat amended the Barnet formula to meet the needs of workers on a small scale and have also arranged A and B to balance each other without disturbing the relative proportions of the ingredients.

A.
Metol 120 grains
Water (cold) 24 ounces

Dissolve _completely_ and then add

Sodium sulphite 2-1/2 ounces
Potassium bromide 15 grains

Shake until completely dissolved but do not apply heat.

B.
Potassium carbonate 350 grains
Water 8 ounces

For use, mix three parts by measure of A and one part of B.

With this developer and a normal exposure, the image should appear in a few seconds and development should be complete in about two minutes. As fast as the prints are developed they should be immersed in

Salt 2 ounces
Water 20 ounces

to stop development. When all are developed, they must be rinsed for a minute or two in clean water and then fixed. Over-exposure is remedied by the addition of potassium bromide solution (as in the case of ferrous oxalate); under-exposed prints should be developed in a weak solution such as

A 3 parts
B 1 part
Water 4 parts

Development will take longer, but the weaker solution will help to bring up the detail without the harshness of the shadows that would be the case if the normal developer was used.

_Hydroquinone and Eikonogen._--The advantage of combining eikonogen with quinol lies in the fact that one provides what the other lacks, the eikonogen tending to give detail without density and the quinol (in inexperienced hands) giving density without detail. The following formula will be found very satisfactory:--

A.
Quinol 40 grains
Eikonogen 120 "
Sodium sulphite 480 "
Citric acid 20 "
Water to 20 ounces

Dissolve the sodium sulphite and citric acid in 15 ounces of water, then add the other ingredients and enough water to make a total bulk of 20 ounces.

B.
Sodium carbonate 60 grains
Sodium hydrate 30 "
Potassium bromide 5 "
Water to 20 ounces

For use, mix one part of A, one part of B and two parts of water. The same remarks as to over and under-exposure apply as in the case of metol.

_Toning Bromide Prints._--The "tone" or colour of the deposit depends largely upon the accuracy of exposure and the developer employed. Ferrous oxalate gives a rich black deposit, but to my mind metol and the combined eiko-quinol give tones at least as beautiful with pretty gray half-tones.

But some people prefer warmer colours, brown and red for instance, and some get brownish blacks (through over-exposure and the use of bromide) which they would like to change.

The colour of the deposit may be changed in various ways by treating the print in baths of different metals. I will give a brief outline of the methods employed, leaving readers to modify them to suit each particular case.

_Black and Blue-black Tone._--Brownish black prints can be much improved after fixing by immersion in a strong bath of gold chloride; the following is the strength used by me:--

A.
Ammonium sulphocyanide 20 grains
Water 1 ounce

B.
Gold chloride 2 grains
Water 1 ounce

When quite dissolved add B very gradually to A, shaking almost continuously. The fixed print should be washed for at least fifteen minutes before toning and should then be placed in a clean tray while the toning bath is poured over it. The solution must be kept moving and the print must be removed and washed directly the desired tone is reached. Prolonged immersion will cause the print to acquire a deep blue tone.

_Brown and Red Tones with Uranium._--Prints immersed in the uranium toning bath gradually become warmer in tone, changing from black to brown and brownish red until they assume a deep red nearly approaching the well-known Bartollozzi chalk.

Prints to be toned by this process must be _thoroughly_ free from hypo or stains will be the inevitable result. The toning bath should be made up as follows, and it must be used at once as it will not keep after mixing A and B:--

A.
Potassium ferricyanide 20 grains
Water 20 ounces
Glacial acetic acid 1 ounce

When quite dissolved add

B.
Uranium nitrate 20 grains
Water 1 ounce

Immerse the print and keep the solution in motion until the desired colour is produced, then wash the print for half an hour in several changes of water acidulated (1 dram in 30 ounces) with acetic acid. Weak, under-developed prints are much improved by this method of toning.

At the end of half an hour, if the whites are at all yellow they may be cleared by immersing the print for a minute or two in the following bath:--

Ammonium sulphocyanide 20 grains
Water 10 ounces

After immersion, rinse the print for five minutes and dry.

_Intensification._--It sometimes happens (especially when too little light has been used to properly judge development) that one acquires a collection of prints that, owing to under or over-development, are useless; let us see how they may be rendered serviceable.

An under-developed print, though weakly looking and "washed out," simply needs intensification to give it the requisite pluck. The foregoing uranium bath acts as an intensifier while conferring a ruddy tone on the deposit. A black deposit can be obtained by intensifying the well-washed print with mercury. The print must first be immersed in a saturated solution of mercuric chloride until the image disappears; it must then be again thoroughly washed to remove all traces of free mercury and may then be redeveloped by flowing over it an old ferrous-oxalate developer. If ferrous oxalate is not at hand, an old metol developer may be substituted, but the former is the more reliable.

When the image is sufficiently intense, the print must once more be thoroughly washed. All the toning and intensifying operations may be conducted by daylight.

_Reduction of Density._--Over dense prints can be made fit for many purposes by means of a "reducer" capable of dissolving part of the deposit. The best for the purpose and the one least liable to cause stains is know as the Belitzski's; it is prepared thus:--

Water 60 ounces
Potassium ferric oxalate 3 "
Sodium sulphite 3 "

Dissolve and add to the red solution so obtained.

Oxalic acid 1 ounce

Shake until the solution turns green and then immediately pour off the solution from any crystals remaining undissolved. To this solution add

Hyposulphite of soda 15 ounces

and shake until dissolved, when it is ready for use.

The print to be reduced need not be free from hypo, but should be rinsed for a few minutes after fixing (or soaked until limp, if previously dried) and may then be placed in a tray and flooded with the reducer. The tray must be well rocked and the print, when sufficiently reduced, must be removed without delay and rapidly washed in running water.

_Some Cheap and Useful Trays._--If large-sized prints are made, the cost of suitable trays becomes a very serious item. The expense of these may be reduced to a mere nothing, without loss of effectiveness, by the substitution of home-made ones. All that is required to make a tray of any size is a thin wooden confectionery box (or the bottom part of a larger case) lined with the shiny white marbled oilcloth known as "American moleskin." This is fitted inside the box (the corners being turned under) and secured by a row of tacks around the top edge. No further lining or preparation is required and the tray will stand all sorts of ill-treatment. As for durability: I had three such trays made out of old herring-boxes picked up at Calgary and lined with moleskin that had already seen service as cover to a wash-handstand and chest of drawers in a Canadian boardinghouse. For upwards of a year those trays were used daily and travelled many hundreds of miles by mule and dog train, and were not worn out when I returned home. My porcelain trays were smashed by a fall from a refractory mule, but the rough and ready makeshifts were a priceless boon.

It seems to me that by practising economy of this kind and in various similar ways (_i.e._, where economy is necessary as, unfortunately, it sometimes is) the cost of practising our pet recreation is very materially reduced.

_W. Ethelbert Henry, C.E._

_The Gum-Bichromate Process._

Pictorial photography is answerable for the revival of this, one of the almost forgotten methods of printing. Results unacceptable to bygone requirements have been reintroduced with advantage, where suggestive individuality and artistic effect have been desired.

The gum process has an unlimited range of possibilities, it would be impossible to describe them all. The minutest details, or the broadest diffusion together with the power of working from the highest to the lowest keys of _chiaroscuro_ are values that can only be realized when the infatuation consequent on successfully working the process is experienced.

This method of printing, as with the so-called "carbon process," is dependent upon the characteristic behaviour of the chromic salts when in combination with organic substances, such as gelatine, gums of various kinds, starch, etc.

When any of these mixtures are submitted to the action of actinic light, they become more or less insoluble.

This property was partially discovered as far back as 1798, by Vauquelin. Professor Sucrow, Mungo Ponton, Beauregard and others advanced its application to photography up to about 1840, but it was not until some ten years later that its great value as a photographic agent was definitely established.

Hunt, Fox Talbot and Poitevin, each worked indefatigably to bring the application of the chromic process to a successful issue; but to Poitevin must be accredited the honour of being the original inventor of the chromated pigment or carbon process. This brings us up to about 1855.

None of these investigators appear to have been remarkably successful, beyond having established definite, but valuable facts of the changes produced.

This want of success may possibly be accounted for by the general employment of gelatine and direct printing. It was not until Pouncey and others, about 1859, employed gum as the colloid medium, that any great advance was made.

About this time an important commission of inquiry decided that to Pouncey, Gamier and Salmon, and Beauregard the honour of producing permanent prints must be equally credited, and accordingly divided the Duc de Luyue's prize between them, giving to Poitevin the credit of the priority of invention.

Pouncey appears to have followed up the process with some considerable success, as some of his existing examples are excellent; it is much to be regretted that we have not more detailed particulars of his methods of working; but he evidently was before his time and met with but little encouragement.

To Alfred Maskell and M. Demachy must be accredited the revival of this long neglected process, and during the last three years much advancement has been made towards perfecting it.

Serious workers, both at home and abroad, are industriously exhausting the possibilities of the process, and crude as some of the earlier examples of this revival have been, improvements and simplicity of working are giving us productions of every description, of such excellent quality that it may soon be expected to satisfy even the caustic criticism that has so persistently opposed its re-introduction.

Dexterity in the various stages of practical manipulation is necessary before skilful efficiency can be secured, and in order to arrive at this, due consideration must be given to the selection of the paper the colour most suitable to the subject and the effect desired.

Almost any kind of paper will be found workable, if it be of fairly good quality. Those that are thickly coated with soluble sizing media are unsuitable, for although they may give clear whites they sometimes produce harsh prints, the half-tones are also liable to be lost in development unless very deeply printed. Several of the continental kinds are well adapted to the process and work in an excellent manner, giving soft and even results; of course, it will be understood that for definition and fine detail the finer grained descriptions are the best, but where diffusion is desired those of a coarser texture may be advantageously used, they give a granulation that tends materially to secure the peculiarities of gradation characteristic of this process.

A few of the continental papers that will be found to work with ease to the beginner, are as follows:--

Michallet paper is rather coarse, but takes the gum coating easily, it has a series of lines running in both directions, which are rather objectionable for some subjects; but it is an excellent paper for first experiments.

Ingrés, is also a paper of similar character, and can be worked with equal facility. Lallane is another paper of the same class, but much finer.

Allongé paper is entirely free from the markings peculiar to those previously mentioned. This paper is best worked on the reverse side, which can be distinguished by examining the name marked in one corner.

Among the English papers the ordinary cartridge, Whatman's drawing papers and many others are adaptable, but it must be borne in mind that those with a toothed or grained surface are preferable.

There are two methods of working, and results of equal excellence have been produced by either. Some of the most proficient workers of the process adopt the easier one of coating the paper, without previous preparation, with a mixture of gum, bichromate of potass and pigment. Others adopt the precaution of first saturating the paper with a strong solution of bichromate, and when dry coating it with a mixture containing only gum and pigment.

Experience is in favour of the previous saturation of the paper, this is recommended especially for beginners, as there are several kinds of paper that will not work efficiently by the first method; but when skill and practical knowledge of the special behaviour of the materials employed is acquired, either method can be adopted.

We may presume that the advantage of the previous saturation of the paper with the chromic salt is, that should there be any inequality in its structural character, or should it be unequally sized, the bichromate appears to act as a kind of resist to the penetration of the pigment, thereby securing an increased range of tone and a corresponding purity of the whites.

The process may be divided into the following operations:--

Saturation or sensitizing of the paper.

Preparation of the gum mucilage.

Mixing and preparing the pigments.

Coating the paper.

Printing and exposure.

Development.

For working by the previously chromated paper method, the sensitizing solution is made up of one part of bichromate of potassium dissolved in ten parts of water. This strength will not keep at all temperatures. Should the salt crystallize out, it is necessary to warm a portion of the solution and re-dissolve the crystals. The solution may be used repeatedly, but it will be necessary to filter it occasionally.

Before saturation it is convenient to cut the paper into the most useful sizes--quarter sheets are handy. Having decided which is to be the working side, mark the back distinctly. Into a dish of sufficient depth pour in the one in ten bichromate solution to a depth of about one inch, and immerse your paper sheet by sheet, until you have in it all you intend to sensitize. As each sheet is placed in the solution, remove air bells and turn it over and repeat this precaution. The time necessary for immersion is of no importance so that the saturation is absolute, about five minutes being generally sufficient for the thickest of papers. By removing the bottom sheet to the top and passing through the whole in this manner, turning over each sheet and removing all air bells, even saturation is secured. Each sheet is carefully and slowly removed from the solution and dried in the dark. The paper is now very sensitive to actinic light, which must during all future operations be carefully guarded against.

After the paper is dry, it will--if kept so--be in good condition for a long time.

To prepare the gum mucilage, take two ounces of Soudan or Turkey gum and dissolve it in five fluid ounces of cold water, strain out the floating impurities through fine muslin, and allow others, and finer to subside. This mucilage will keep in good condition in a well-corked bottle, for a considerable time. M. Demachy employs gum mucilage of twice this density.

Pigments in powder are more suitable than in any other form, if in cakes or paste. The medium in which they are prepared, does not work kindly with the gum, and it is also difficult to accurately measure quantities. No advantage is gained by using expensive colours, they can all be purchased at a good colourman's, and at a small cost.

Lamp or any carbon, black, red ochre, yellow ochre, burnt sienna, and raw sienna, all work well; there is some uncertainty with the umbers and sepias. It will be found that much time will be saved if a combination of these dry colours is made up in bulk, as for instance--one hundred and seventy-five grains of vegetable black and one hundred of burnt sienna, give a rich soft brown colour. These must be finely and intimately mixed with each other, which is conveniently accomplished by grinding with a small pestle and mortar; after which the mixture may be kept in a wide-mouthed bottle. Another advantage in thus keeping combinations of dry colours in bulk, is the absolute certainty of repeating the actual tint when required.

Various combinations of similar mixtures can be made. Of course it will be understood that any or all of the above-named colours may be used singly.

The grinding of the pigment with the mucilage is easily done on a stone slab with a palette knife. Take half a fluid ounce of the two in five gum mucilage, to which add the same quantity of water and thoroughly mix. Weigh out fifteen grains of the mixed pigment and place in a heap on the slab, add a few drops of the diluted mucilage, grind and regrind the mixture until it is completely smooth, then remove it to a cup, and clean the stone with another portion of the reduced mucilage, finally adding the whole of the ounce, intimately mix, and it is then ready for coating the paper.

For extra fine work on smooth paper, and in fact for all classes of work, the fine grinding of the colours adds materially to extend the range of gradation, and although the trituration may be carried out fairly well with a palette knife, when the finest possible grades are desired, recourse must be had to the muller and stone. Mullers are obtainable of any artist's colourman, they are made in glass, and a convenient size is about one inch in diameter.

The most convenient brush for applying the mixture of combined gum and pigment to the paper, is of the description known as bear's hair, these are usually set in tin; a flat one about two inches wide is a useful size.

In order to coat the paper evenly, pin it down to a drawing board by each corner with a double layer of blotting paper an inch or two larger than the paper to be coated. The blotting paper will absorb the excess of colour at the margins and enable you to secure an even coating up to the extreme edge.

Take a fairly full brush of the mixture after thoroughly incorporating the colour and spread it evenly over the paper, crossing and recrossing it with the brush. Allow the mixture to lie upon the paper for a second or two so that the paper may expand; now release each of the corners and pin the paper down again. Upon the next operation depends the evenness of the coating.

Take a four inch wide artist's badger's hair softener, hold it vertically and lightly by two fingers and the thumb about an inch and a half from the top of the handle, and pass it rapidly over the whole surface of the paper as quickly and evenly as possible. The motion producing the best effect is not the usual sweeping action, but a series of sudden short jerks, difficult to describe but easily acquired. Continue this softening down until the paper has an even semi-transparent surface without uneven cloudy spots. Allow it to dry spontaneously, but before it is stored for future use dry it carefully by the fire, but avoid overheating.

Uncertainty of result is a defect often brought into argument against this process; but absolute uniformity is not difficult if strictly accurate quantities only are employed. With constant strength of bichromate and gum, uniform weights and combination of pigment, similarity of repeats are obtained: but these can only be secured when each sheet of paper is coated identically with its fellow. To get this evenness the badger hair softener must be washed out and dried after coating each sheet. This is very quickly accomplished by an energetic shaking and drying upon a smooth towel. If the paper has been coated properly, it has an even semi-transparent surface slightly glassy.

Failures often occur from using an excess of pigment and allowing the gum to become too thick in consequence of evaporation. Excess of pigment gives dense heavy shadows and increases the difficulty of printing; excess of gum gives clear high-lights, tending to hardness and easy solubility endangering the half-tones.

The paper, if it has been correctly coated will work satisfactorily, if on steeping a small piece of it downwards upon cold water, the pigmented gum dissolves and drops from the surface leaving the paper nearly clean. From ten to fifteen minutes should complete this test.

The method of working without previously chromatizing the paper is as follows:--Take half a fluid ounce of four-in-ten gum mucilage and add to it an equal quantity of saturated solution of bichromate of potass; to this, with all care as to grinding and mixing, add the pigment; coat the paper as before directed. This method will be considerably slower in printing than that in which the paper had been previously saturated with the bichromate; neither are the whites as a rule quite so clear; but it will possess a peculiar grain and softness not otherwise obtainable, which is much approved by some workers of the process.

Exposure is so much dependent on circumstances that it is difficult to give precise directions, being governed by the density of the negative, the thickness of the coating and the intensity of the light. Even and not too dense negatives are the more suitable, for if the intermediate and high-lights are over dense the shadows are considerably over printed before the lighter parts can be brought out. Skill in development can do much to overcome these defects, but they may be considerably modified by the judicious employment of matt varnish, and by other methods of locally retarding printing.

The greatest assistance in obtaining uniformity in printing is the employment of a reliable actinometer, Wynne's print meter is probably the most useful for this purpose, with ordinary gelatino-chloride paper as a register; from twelve to sixteen numbers will be mostly sufficient for an ordinary negative, on not too thickly coated paper. Another method of judging exposure is by the appearance of the shadows; they may frequently be seen by transmitted light, and when well out printing may be judged to be correct, but this is a slovenly method and only approximately correct at the best.

If the bichromate is used only in the pigmented gum, without previous saturation of the paper, exposure must be much more prolonged.

By no other process is it possible to obtain such diversity of effect as by this; much will, however, depend on the skill which is exercised in development. Should the printing exposure have been fairly correct it is a simple procedure. The print is floated face downward upon cold water contained in a deep dish; see that all parts are equally acted upon by the water, and that no air bells exist; if any, they may be easily removed by gently raising the print and immersing it again once or twice. After it has been soaking some five or ten minutes it may be examined; if all is going well, and the exposure has been approximately correct, the pigmented gum on the unexposed margins will have left the paper, and possibly some of the high-lights and half-tones may be making an appearance, if so, the treatment must be of a gentle character, and the print may be safely left for some time longer in the same position face downward; never allow it to lie either in or out of the water face upwards for any long time, or unremovable stains will be developed. Many prints will develop almost entirely without assistance, or with only an occasional laving of water if allowed to lie in this position for a long time. On the other hand some may, even when only slightly over-printed, give no indication of development. When this is the case remove the print from the water and place it face upwards upon a thin, smooth board, fix it in position with one drawing pin on the extreme margin, then gently lave cold water over it; should some of the darker parts still resist this action, longer soaking will be found advantageous. If there are still parts on which the colour will not move, recourse must be had to the brush, and for this purpose nothing is better than a large camel's hair mop. Keeping the brush always full of water, touch where necessary very softly; do not sweep it up or down, but just dab here and there as may be required, constantly flowing over the surface a copious supply of water.

If there are still parts in the shadows, or even in the high-lights that will not move, a jet of water from an enema syringe or from the household service pipe is very useful.

As a last resource a prolonged steeping in water of varying degrees of temperature, even up to the boiling point, may be resorted to, but the application of increased temperature requires judicious management.

When the print is sufficiently developed, if the creamy yellowness of the chromate stain is not desired, the print must be cleared or bleached, either in a solution of alum, sulphite of soda, or hyposulphite of soda, strength being immaterial with a careful after-washing. If the print is only just sufficient or only slightly over-printed, care must be taken that the clearing bath is not acid, neither must the washing be too prolonged, but if the print is first dried and submitted to light, this precaution is unnecessary.

Always allow the prints to dry spontaneously. It will not do to use any kind of pressure or blotting paper, for the surface of the colour is very tender and delicate.

_Jas. Packham, F.R.P.S._

_An Introduction to Carbon Printing for Beginners._

In the article that follows next will be found a complete exposition of the carbon process, with its various adaptations from the preparation of the paper and material forwards.

Whilst at the present time carbon printing is more largely used by professional photographers, yet its simplicity, the absence of chemical formulæ and complications combined with the beauty of the results, makes it eminently suitable for amateur workers, and hence it has been thought desirable that as an introduction to the subsequent article, a brief and simple outline of the process should be given for the benefit of those who have not hitherto made its acquaintance.

In the first place then let it be understood that in carbon printing instead of depending on light to make a visible alteration of the sensitive salts as in silver printing, we expose the prepared paper or "tissue," as it is called, under a negative and secure a positive in insoluble gelatine, the gelatine having combined with it a pigment, and hence we get an image in pigment, not in platinum, or silver, or gold, but in a simple pigment which may be of any colour.

If bichromate of potash is mixed with an organic substance such as gelatine, that gelatine becomes insoluble after exposure to light, and if that gelatine carries with it a pigment, then on becoming insoluble it holds the pigment with it. If now, paper or other material be coated with bichromate, gelatine, and pigment, and exposed to light under a negative in the usual way, the thin portions of the negative will admit of the light acting on this coating and making it insoluble, whilst the parts which are protected from light, as for instance the sky or white objects, will remain unchanged and soluble, and on being washed in water will dissolve away, leaving white paper, whilst the light-affected portions which have become insoluble remain in proportion as the light has penetrated the various densities of the negative. This then is how we obtain our print.

For fuller explanation of the paper or "tissue" and its manufacture the reader is referred to the next article.

The beginner will certainly first obtain his tissue ready made, and he can purchase it ready sensitized or otherwise. The former will be best at the outset, but it must be borne in mind that it should not be kept longer than can be helped before use, and never more than ten to fourteen days at the utmost. Various shades of blacks, browns, and reds are the usual colours, also grey, green, and blue. The tissue is rather more sensitive to light than silver paper, and should therefore be opened and handled in subdued light. It must be kept as dry as possible. A rather vigorous negative is best for carbon printing, one not too strong in contrasts. Before placing the negative in the frame, we must give it what is termed a "safe edge." This is done by making a narrow border, say of about a quarter of an inch or less, round the negative, either on the glass or film side, with opaque black varnish, or it may be done by gumming on narrow strips of paper, such as lantern-slide binders. If binders and not black varnish are used, they must be applied to the glass side.

The Carbon printing paper which will hereinafter be called the "tissue" will be found to present an unpromising appearance, and as the coating is the full colour of the pigment in which the print is eventually to appear, it follows that the progress of printing will not be visible, and a mechanical means of gauging the exposure must be resorted to. An actinometer, similar to that described in the article on Platinotype, will do, and another and simpler form is described in the next article.

Printing will occupy about one-third of the time occupied by gelatino-chloride of silver paper.

Development is conducted in daylight, but not too close to a window.

The absence of chemical solutions has been suggested as an advantage, in this process the developer being merely hot water.

It is not necessary to have this laid on, a can of hot water close at hand and a kettle on the fire or gas stove not far off are all that are required.

We shall require four or five dishes, one at least of which should be a good deal larger than the size of the prints we are to develop and several inches deep--a good-sized pie-dish or a basin will do.

Development merely consists of washing away the unaffected and therefore soluble coating, but it must be remembered that the less affected portions representing the half-tones have received their modicum of light on the surface, and therefore the soluble part of the film is underneath the part that has like a surface skin become insoluble. This necessitates the printed film or tissue being transferred to another paper or "support," so that we may develop or wash away from the back.

In procuring your carbon tissue order at the same time a packet of Single Transfer Paper, which is paper with a thin coating of hard gelatine. Now to proceed. Place a piece of single transfer paper into a dish of cold water, and in three or four minutes the coated side will feel slimy, then place in the same dish a piece of the printed tissue face upwards. This will probably curl up at first and afterwards flatten out again. When this has happened or in a few minutes after immersion bring the piece of single transfer paper and the print together, film to film, so that they may be in contact, and square one with the other. Now holding them by one edge, withdraw them together by sliding them out of the dish on to a sheet of thick glass, a large cutting glass serves well, or stout sheet of zinc.

This should be supported in readiness at the rim of the dish.

Having the transfer paper and print now on the glass or zinc, hold them firmly and with a rubber squeegee press them closely into contact, squeezing as much water out as possible.

A better way perhaps is, if the dish is large enough, to place the glass or zinc under the two papers whilst in the water and so raise them out.

The squeegeeing must be done thoroughly, firmly, and all over--several strokes being given in each direction.

Next lift the papers, now in firm contact and sticking together, and place them between blotting paper on which is a heavy weight. The next print may now be proceeded with and so on.

The print should be between blotting paper and under pressure for about twenty minutes, after which it is removed to a dish of hot water--almost as hot as the hands can comfortably bear, say 100° to 120° F.

After lying in this for a few moments the dark pigment will be seen to be oozing out from between the two papers. When this has begun to come pretty freely take one corner of the print and pull it away from the transfer paper. It should come quite easily, and on being peeled off entirely it is thrown away. We have now the transfer paper bearing the printed film reversed, that is, the side which was previously at the bottom and next the original paper support, is now uppermost and can therefore be got at.

If we splash it or lave it with the hand, using the hot water, we shall soon see what happens. The smudgy mass of pigment begins to wash away and the picture gradually appears.

This constitutes development and we continue working it with hot water until the whole is clear and bright, being careful not to touch the film with fingers or anything but water, for being in a very delicate and soft condition it would be certain to sustain injury.

The hotter the water the greater its washing-off action, and hence in cases of over-exposure very hot water may go far to recover the print. When the desired result is secured, transfer the print to a dish of cold water, this instantly tends to slightly harden the film by cooling it, and after two or three minutes it is passed into a dish of alum and water, which further hardens it and also "clears" the print of any bichromate salts which may still remain. In the alum bath the print should remain until any sign of yellow stain has disappeared, when after a final rinse of a few minutes in cold water to remove the alum, the print may be hung up to dry.

It will be seen that there is no prolonged washing as with those processes in which hypo is employed, and the print is absolutely permanent.

It must be remembered, however, that in the finished picture we are looking at the back of the printed film as it received the light impressions from the negative, and hence the image is reversed, that is, the left is on the right and the right on the left. For landscape and views this reversed position will probably be of no importance, but if it is desired to have things right way round--in portraits it will be essential--we must either work from reversed negatives, or we must again transfer the film which will then constitute a _double_ transfer. We shall now understand why previously we called the paper to which the film was transferred _single_ transfer.

Inasmuch as it will be seen that the print is not on paper, but consists of a transferable film of pigmented gelatine, it will be understood that the paper employed is merely a support to that film, hence it is customary to speak of the paper as the support, whilst moreover it maybe, and as often as not is ivory, glass, textile fabrics, wood, or other substances.

If now we wish to again transfer the film so as to correct the lateral reversal, we substitute for the single transfer paper a "_temporary_ support."

The temporary support which is to receive the film merely whilst it is being developed, and with the intention of its being subsequently transferred again to a _final_ support, may be paper or many other things.

Moreover, remembering that the film is mainly gelatine, it should be clear that whatever the nature of the surface of the temporary support, the soft glutinous film will take that surface just as we may make the impression of a seal in sealing-wax.

The normal carbon print is shiny, due to the gelatine, and so, if as a temporary support we were to use ground glass or matt "opal," the carbon print film would receive the fine granulated surface and give a matted print as a result. This merely by the way as suggesting an additional advantage offered by the double transfer process as a set-off against the slight extra trouble.

If double transfer is determined upon, and it is not intended to experiment with ground glass, etc., then when purchasing the carbon tissue, some _temporary_ support (sheets of paper coated with gelatine and shellac) should be procured, also some pieces of _final_ support.

Whatever the temporary support, it must receive an application of waxing solution. This also may be bought, or can be made of:--

Yellow resin 36 grains.
Yellow wax 12 "
Ether 2 ounces.

Melt the wax, add the resin, stir together and then add the ether.

Pour a little of this mixture on to the temporary support and spread with a tuft of cotton wool, and rub over to make it even.

The final support for double transfer may be purchased, and is made ready for use by soaking for ten minutes in alum.

The temporary support, after being waxed and the waxing solution having become dry, is to take the place of the single transfer paper in every respect, and the film developed as already described. When it has reached the final washing, after the alum clearing bath, it is brought into contact with the final support (which has been for ten minutes in alum bath as just described) and is removed to the glass or zinc plate and squeegeed.

It is now hung up to dry, and when quite dry the blade of a knife should be inserted at one corner and the temporary support gently pulled off.

Such is the carbon process, neither difficult nor lengthy, and with this brief outline to form an introduction, the reader who is a tyro will the better appreciate the fuller description which follows.

* * * * *

Whilst the article that follows is more comprehensive than the beginner may require at first, he is nevertheless advised to read it carefully through, and some points which may not seem clear at first will explain themselves after a very little experience.

_The Carbon Process._

Before proceeding to practical details of working, it may be as well to realize what a piece of carbon tissue is, and what takes place in the process of exposing such tissue to light. Mr. J. W. Swan, who is to be regarded as the inventor of carbon process as we now know it, was justified in giving the name "tissue" to the film of pigmented bichromatized gelatine, as at first it was a tissue unsupported by paper backing and containing pigment practically, if not entirely, carbon. The terms "carbon" and "tissue" have been generally accepted as describing a pigmented paper containing permanent colour, therefore little if any misunderstanding is caused by such general description. The carbon process, like other kindred methods, is based upon the well-known hardening action of light upon a bichromate salt in combination with organic matter. When paper is coated with a mixture of gelatine pigment and a bichromate salt, dried under favourable conditions and exposed to light under a negative it naturally follows that a positive image is produced. The negative acting as a screen, prevents any undue hardening of such portions of the picture as are intended to form the high-lights, only slightly interfering with what are to be the middle tints, and practically permitting full play in the shadows. The latent image is imprinted on and into the film of tissue compound with the most delicate portions on the surface, and means must therefore be adopted to protect the surface during the washing away of all parts of the film not intended or desired to form any part of the finished picture.[7] In Swan's process this object was secured by cementing the surface of the printed tissue to its temporary support with rubber solution, but after J. R. Johnson discovered that the printed tissue would adhere without any cement to any surface impervious to air and water simply by atmospheric pressure, the same end was gained by soaking the undeveloped print in water until about _half saturated_, then bringing it into contact _under water_ with either its temporary or permanent support, slightly squeegeeing or sponging to remove as much water as possible without injury to the print; as to _air_, _there ought not to be any present_ if care is taken to exclude it before lifting from the water bath. The half-soaked tissue after mounting absorbs every particle of water from between the surfaces, and thus secures optical contact.

[7] It is generally asserted by non-practical carbon printers
that all portions of the film behind that which finally forms
the print, are unacted upon by light. That is to say,
unchanged and quite as soluble as if not printed at all. The
upholders of such a theory should try the following
experiment:--Take a piece of tissue, cut it through the
centre, expose one piece, then mount both under precisely
similar conditions and wash in the same warm water bath.
Paying special attention to the backing papers, they will
find the one unacted upon by light will have parted with its
load of coloured material in much less time than the piece
that formed the backing of the print.

The squeegee, handy tool as it is, ought to be used with great care, in no case with any degree of force, or serious injury will result, particularly to the finer kinds of work, such as double transfer prints of all kinds, either on paper, ivory or opal. The rubber edge of the squeegee should be free from notches, often caused by contact with the sharp edges of glass plates. The notches can be removed by rubbing on a sheet of glass paper placed on a plane surface.

TISSUE MAKING.

The tissue compound consists of a mixture of the following ingredients:--Gelatine, sugar, pigment and water. The proportions are of infinite variety according to season, the nature of the pigment used, and the purpose for which the tissue is intended. For convenience it is the rule for tissue makers to prepare what is termed stock jelly by dissolving, by the aid of a water bath, gelatine and sugar in water, in varying proportions--roughly speaking:--

Gelatine 2 parts.
Water 4 to 7 "
Sugar[8] 3/4 to 1-1/4 "

[8] For some purposes (instead of sugar), glycerine, sugar of
milk, or treacle may be substituted.

The pigments are made up into what are termed jelly colours, which are ground either by hand on a slab of glass, marble or granite, using a suitable muller for the purpose, or when large quantities are required a paint mill driven by steam or other power is employed. In hand grinding the colour is kept moist by syrup on greatly reduced stock jelly. After grinding by hand the pigment is lifted from the slab with a palette knife and stirred into melted stock jelly. When the mill is used, the pigment is mixed with the jelly before grinding. The proportion of pigment to jelly varies enormously according to the nature of the pigment, and may be anything between 2-1/2 per cent. and 25 per cent. Having prepared stock jelly and jelly colours, and allowed both to set, they are weighed out in proper proportions, the jelly being dissolved in a tin vessel placed in a water bath. The colour, generally speaking, is dissolved in a small proportion of the stock jelly placed in the mill and again ground into the bulk of the jelly. In some cases the pigment is dissolved in warm water and filtered through cotton wool, fine felt or flannel. After adding powdered recrystallized bichromate, the jelly compound is ready for coating or spreading on the paper. The coating may be done by hand or machine. Several forms of machine are in use, including the first form invented by Mr. Swan. When only a small quantity is required, it is the general practice to coat by hand.

In hand coating, the tissue compound may be strained through fine muslin into a flat tin dish placed on a water bath; the surface cleared of air bubbles by dragging over it a strip of stiff paper. The sheet of paper to be coated is held in an upright position at the further end of the dish with its bottom edge just touching the surface of the solution, gently lowered until the whole surface of the sheet is in contact with the solution. If the lowering is properly done there will not be any default in contact, but if allowed to rest on the solution a few moments, the presence of air bubbles, if any, will be detected by the presence of little lumps on the back of the paper, these may be removed by raising a corner and touching the spots with a finger tip. The sheet is then raised with a rather slow and steady motion, allowed to drip, then clipped to a line by its top corners and left to dry in a warm dry room from which white light has been excluded. When this method of coating is adopted it is best to have the sheets of paper an inch longer than the dish; the blank edge prevents contamination of the fingers and distortion of the sheet caused by contraction in drying. Another method of hand-coating is to roll the sheet into a tube shape, placing the roll on the surface of the jelly compound one and a half inches from the top of the free end, raising with rather slow and steady motion as before. When the second method is chosen an oblong and somewhat deep dish will be found better than the flat shape; the flat dish may be used if tilted to give greater depth of solution in a corner.

In the manufacture of tissues the greatest care must be taken to avoid over or long-continued heating of the gelatine solution. Either a too high temperature or a lower temperature, long continued, destroys the solution by rendering a considerable portion of it soluble in cold water and to a great degree reducing its gelatinous character.

The samples of gelatine used in tissue making are of two kinds, although both of good quality they differ in solubility, in hot weather a larger proportion of the "hard" sample is used, in cold weather _vice versa_.

INSENSITIVE TISSUES.

All insensitive tissues are made with a single sample of hard gelatine. They are stocked by dealers and must of necessity be fit for use at any season of the year, to say nothing of those exported to hot climates.

TRANSFER PAPERS.

Papers of many kinds are necessary for single transfer prints, the tint of the paper must blend and harmonize with the tone of the tissue or by contrasting help to produce a pleasing effect. For prints of warm tones such as red chalk, terra cotta and the various tints of sepia, a yellowish or cream-toned paper forms the most harmonious basis; the various tints of black, blue, and purple look best on a slightly bluish-tinted paper. For instance, a copy of an old engraving in tissue, of the brown tone of the original would be utterly spoilt by a blue-tinted basis. The above remarks apply only in a limited degree to double transfer papers which in general use are confined almost exclusively to portraiture. Such papers are sometimes modified by tinting mauve, rose, opal, etc., etc. Such tints are only in small demand and are in all cases confined to papers coated with enamel preparations. The best and most durable form of double transfer paper is that prepared on fine chemically pure paper with colourless gelatine and made insoluble by the smallest possible quantity of chrome alum, entirely without white or tinted pigment of any kind. The best variety of double transfer paper only differs from the finest form of single transfer paper in having on its surface a rather thicker and softer coating of colourless gelatine.

All transfer papers, either for single or double transfer, may be coated in the same way as tissue, with the exception of those having a very rough surface. All drawing papers and in fact all papers of very rough surface are prepared by brushing over their surfaces several coatings of a very thin solution of gelatine containing a larger proportion of chrome alum or formalin than is used in making ordinary single transfers. A flat camel-hair brush is best for this form of coating, care must be taken to avoid air bubbles.

FLEXIBLE TEMPORARY SUPPORT.

Is paper coated with a gelatine solution in the first instance, and after drying, again coated with an aqueous solution of shellac.

SENSITIZING THE TISSUE.

Pour the bichromate solution into a deep flat dish (porcelain, ebonite, zinc, wood or tin) to the depth of half an inch to an inch; place a sheet of tissue in it face upwards, remove air-bubbles with a camel-hair brush or soft sponge, using as little pressure as may be; turn the sheet and remove bubbles formed on the paper, turn the sheet again face upwards, and passing brush or sponge gently over the surface, keep it evenly wet until it is fairly limp; remove from the solution, place face downwards on a perfectly clean glass or zinc plate, squeegee to remove excess of solution, blot or wipe with a soft cloth, remove any solution from the fingers, lift from the plate, handle by edges only, clip to a line, small sizes by one corner only, larger sheets by two corners, leaving a little slackness between the two clips to allow for contraction in drying, otherwise the sheet will be distorted and difficult to press into contact with the negative.

The sensitizing _may_ be done in ordinary daylight. The drying _must_ take place in a room from which actinic light is excluded, and in a current of warm dry air, free from impurities, such as the products of combustion from burning gas, or an escape of sewer gas, etc., and at a temperature not higher than 120° F. The drying should be done as quickly as possible, otherwise the tissue's keeping property will be greatly reduced, and in all probability a thin film formed on the surface, of insoluble gelatine, known to printers as "decomposed tint," degrading the high-lights, and, except in the case of very "hard" negatives, spoiling the work.

It will be evident to anyone that the fancy forms of sensitizing have been carefully avoided--floating on the back, floating on the face, etc., etc. All the results desired can be obtained by immersion. If a hard negative has to be dealt with, a stronger solution, or longer soaking in the bichromate solution, is all that is needed; for weak negatives _vice versa_.

_Note._--In the dry frosty air of winter, sensitized tissue will dry without heat, and continue soluble for a considerable length of time, often as long as a month, or even longer.

In hot weather it is recommended that the solution of recrystallized bichromate be made immediately before using, as in dissolving the crystals a considerable reduction of temperature is produced. Should the temperature then be over 60° F., ice must be used, not in the solution, but roughly broken up and mixed with salt in an outer vessel. If ice is placed in the bichromate bath allowance must be made by keeping out part of the water. The ice should be encased in several thicknesses of fine muslin to prevent the solid impurities it generally contains getting into the solution. When recrystallized bichromate is not procurable, a few drops of liquid ammonia added to solution of crude bichromate is recommended. As bichromate is cheap, a fresh solution should be made for each large batch of tissue.

PRINTING THE NEGATIVE.