PhotoHistory

From: THE BARNET BOOK OF PHOTOGRAPHY

By Thomas S Skelton 1898

An Introduction to Carbon Printing for Beginners.

In this article 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 formulas 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, 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 color.

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 pro portion 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 colors, also gray, 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 color 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 gelatine-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.

When obtaining 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. The paper should curve upward at the edges, then flatten out after a few moments.

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 dis appeared, 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 not, 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 oi 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 pur chased, 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 introduc tion, 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.