ON THE SIMPLICITY OF THE CALOTYPE PROCESS, BY DR. DIAMOND.

(Read before the Photographic Society, Nov. 3, 1853.)

I feel that some few words are required to explain to the Society the reasons which have induced me to call their attention to a branch of photography, which of all others has been dwelt upon most fully, and practised with such success by so many eminent photographers.

The flourishing state of this Society, which is constantly receiving an accession of new Members, indicates the great number that have lately commenced the practice of photography, and to those I hope my observations will not prove unacceptable, because of all others the calotype process is undoubtedly the simplest, and the most useful; not only from that simplicity, but from its being available when other modes could not be used.[[2]]

I am also induced to urge on the attention of the Society the advantages of this, one of the earliest processes, because I think that there has been lately such an eager desire for something new, that we all have more or less run away from a steady wish to improve if possible the original details of Mr. Fox Talbot; and have been tempted to practise new modes, entailing much more care and trouble, without attaining a correspondingly favourable result.

Amongst antiquaries I have long noticed, that many who have especially studied one particular

branch of archæology, think and speak slightingly of those departments in which they are not much interested. One fond of research in the early tumuli is esteemed to be a mere "pot and pan antiquary" by one who, in his turn, is thought to waste his time on "mediæval trash;" and this feeling pervades its many sections.

I hope I shall not give offence in saying, that amongst photographers I have noticed somewhat of a similar spirit, namely, an inclination to value and praise a production, from the particular mode of operation adopted, rather than from its intrinsic merits. The collodion, the waxed paper, or the simple paper processes have merits pertaining to themselves alone; and those who admire each of these several processes are too apt to be prejudiced in favour of the works produced by them.

Before proceeding farther, permit me to observe, that if some of my remarks appear too elementary, and too well known by many assembled here, my reason for making them is, that I have myself experienced the want of plain simple rules, notwithstanding the many able treatises upon the subject which have already been written: I hope, therefore, I shall receive their pardon for entering fully into detail, because a want of success may depend upon what may appear most trivial.

I think the greatest number of failures result from not having good iodized paper; which may be caused by

1. The quality of the paper;

2. The mode of preparing it;

3. The want of proper definite proportions for a particular make of paper;

because I find very different results ensue unless these things are relatively considered.

I have not met with satisfactory results in iodizing the French and German papers, and the thick papers of some of our English makers are quite useless.

Turner's paper, of the "Chafford Mills" make, is greatly to be preferred, and therefore I will presume that to be used, and of a medium thickness. The great fault of Turner's paper consists in the frequent occurrence of spots, depending upon minute portions of brass coming from the machinery, or from the rims of buttons left in the rags when being reduced to pulp, and thus a single button chopped up will contaminate a large portion of paper; occasionally these particles are so large that they reduce the silver solutions to the metallic state, which is formed on the paper; at other times they are so minute as to simply decompose the solution, and white spots are left, much injuring the effect of the picture.

Whatman's paper is much more free from blemishes, but it is not so fine and compact in its texture; the skies in particular exhibiting a minutely speckled appearance, and the whole picture admitting of much less definition.[[3]]

All papers are much improved by age; probably in consequence of a change which the size undergoes by time. It is therefore advisable that the photographer, when he meets with a desirable paper, should lay in a store for use beyond his immediate wants.

It may not be inappropriate to mention here, in reference to the minuteness attainable by paper negatives, that a railway notice of six lines is perfectly legible, and even the erasure for a new secretary's name is discernible in the accompanying specimen, which was obtained with one of Ross's landscape lenses, without any stop whatever being used, and after an exposure of five minutes during a heavy rain. The sky is scarcely so dense as could be desired, which will be fully accounted for by the dull state of the atmosphere during the exposure in the camera.

Having selected your paper as free from blemishes as possible, which is most readily ascertained by holding it up to the light (as the rejected sheets do perfectly well for positives, it is well to reject all those upon which any doubt exists), mark the smoothest surface;—the touch will always indicate this, but it is well at all times not to handle the surfaces of papers more than can be avoided. There is much difference in various individuals in this respect; some will leave a mark upon the slightest touch, whereas others may rub the paper about with perfect impunity.

I prefer paper iodized by the single process; because, independently of the case and economy of time, I think more rapidity of action is attained by paper so treated, as well as that greater intensity of the blacks, so requisite for producing a clear picture in after printing.

To do this, take sixty grains of nitrate of silver and sixty grains of iodide of potassium, dissolve each separately in an ounce of distilled water, mix and stir briskly with a glass rod so as to ensure their perfect mixture; the precipitated iodide of silver will fall to the bottom of the vessel; pour off the fluid, wash once with a little distilled water, then pour upon it four ounces of distilled water, and add 650 grains of iodide of potassium, which should perfectly redissolve the silver and form a clear fluid. Should it not (for chemicals differ occasionally in their purity), then a little more should be very cautiously added until the fluid is perfectly clear.

The marked side of the paper should then be carefully laid upon the surface of this fluid in a proper porcelain or glass dish. Then immediately

remove it, lay it upon its dry side upon a piece of blotting-paper, and stroke it over once or twice with a glass rod; this as effectually expels all the particles of air as complete immersion; it is also more economical, and has the advantage of requiring much less time in the after-immersion in the hypo. when it is required to remove the iodide. Either pin the paper up, or lay it down upon its dry side, and when it becomes tolerably dry (perfect dryness is not requisite), immerse it in common cold water for the space of four hours, changing the water during that time three or four times, so that all the soluble salts may be removed; often move the papers, so that when several sheets are together, one does not press so much upon another that the water does not equally arrive at all the surface.

If this paper is well made, it is of a pale straw colour, or rather primrose, and perfectly free from unevenness of tint. It will keep good for several years; if, however, the soluble salts have not been entirely removed, it attracts damp, and becomes brown and useless or uncertain in its application.

Some of our oldest and most successful operators still adhere to and prefer the iodized paper prepared by the double process, which certainly effects a saving in the use of the iodide of potassium. The following is the easiest way of so preparing it:—Having floated your marked surface of the paper on a 30-grain solution of nitrate of silver, and dried it[[4]], immerse it for 20 minutes in a solution of iodide of potassium of 20 grains to the ounce, when it immediately assumes the desired colour. It is then requisite, however, that it should undergo the same washing in pure water as the paper prepared by the single process.

Upon the goodness of your iodized paper of course depends your future success. Although it is not requisite to prepare it by candle-light (which in fact is objectionable from your inability to see if the yellow tint is equally produced), I think it should not be exposed to too strong a light; and as the fly-fisher in the dull winter months prepares his flies ready for the approaching spring, so may the photographer in the dull weather which now prevails, with much advantage prepare his stock of iodized paper ready for the approach of fine weather.[[5]]

Many other ways of iodizing paper have been recommended which have proved successful in different hands. Dr. Mansell, of Guernsey, pours the iodide solution upon his paper, which previously has had all its edges turned up so as to resemble a dish; he rapidly pours it off again after it has completely covered the paper, and then washes it in three waters for only ten minutes in all: he considers that thereby none of the size of the paper is removed, and a more favourable action is obtained. In the experiments I have tried with the use of the air-pump, as recommended by Mr. Stewart, I have met with much trouble and little success; and I am inclined to attribute the very beautiful specimens which he has produced to his own good manipulation under a favourable climate.[[6]]

To excite the paper take 10 drops (minims) of solution of aceto-nitrate of silver, and 10 drops of saturated solution of gallic acid, mixed with 3 drachms of distilled water.

The aceto-nitrate solution consists of—

Nitrate of silver 30 grains.
Glacial acetic acid 1 drachm.
Distilled water[[7]] 1 ounce.

If the weather is warm, 6 drops of gallic acid to the 10 of aceto-nitrate will suffice, and enable the prepared excited paper to be kept longer.

This exciting fluid may be applied either directly

by means of the glass rod, or by floating, as before, and then the glass rod. But if floating is resorted to, then a larger quantity must be prepared. As soon as it is applied the paper should be blotted off by means of blotting-paper (which should never be used more than once in this way, although preserved for other purposes), and put into the dark frames for use.[[8]] It is not requisite that the paper should be perfectly dry. This exciting should be conducted by a very feeble light; the paper is much more sensitive than is generally supposed; in fact, it is then in a state to print from by the aid of gas or the light of a common lamp, and very agreeable positives are so produced by this negative mode of printing.

I would advise the aceto-nitrate of silver and the solution of gallic acid to be kept in two bottles with wooden cases differing in their shape, so that they may not be mistaken when operating, in comparative darkness. A ¼ of an ounce of gallic acid put into such a 3-ounce bottle, and quite filled up with distilled water as often as any is used, will serve a very long time.

I would also recommend that the paper should be excited upon the morning of the day upon which it is intended to be used; no doubt the longer it is kept, the less active and less certain it becomes. I have, however, used it successfully eight days after excitement, and have a good negative produced at that length of time. The general medium time of exposure required is five minutes. In the negatives exhibited, the time has varied from three minutes to eight, the latter being when the day was very dull.

The pictures should be developed by equal quantities of the aceto-nitrate of silver and the saturated solution of gallic acid, which are to be mixed and immediately applied to the exposed surface. This may be done several hours after the pictures have been removed from the camera. Care should be taken that the back of the picture does not become wetted, as this is apt to produce a stain which may spoil the printing of the positive.

If upon the removal of the paper from the dark frame, the picture is very apparent, by first applying little gallic acid, and immediately afterwards the mixed solutions, less likelihood is incurred of staining the negative, which will be more evenly and intensely developed. If a browning take place, a few drops of strong acetic acid will generally check it.

Should the picture be very tardy, either from an insufficient exposure, want of light, or other cause, a few drops of a solution of pyrogallic acid, made with 3 grains to the ounce of water, and a drachm of acetic acid, will act very beneficially. It sometimes gives an unpleasant redness upon the surface, but produces great intensity upon looking through it. Until the pyrogallic solution was added, there was scarcely anything visible upon the specimen exhibited, the failure having in the first instance happened from the badness of the iodized paper.

As soon as the picture is sufficiently developed it should be placed in water, which should be changed once or twice; after soaking for a short time, say half an hour, it may be pinned up and dried, or it may at once be placed in a solution almost saturated, or quite so, of hyposulphite of soda, remaining there no longer than is needful for the entire removal of the iodide, which is known by the disappearance of the yellow colour.

When travelling it is often desirable to avoid using the hyposulphite, for many reasons (besides that of getting rid of extra chemicals), and it may be relied on that negatives will keep even under exposure to light for a very long time. I have kept some for several weeks, and I believe Mr. Rosling has kept them for some months.

The hyposulphite, lastly, should be effectually removed from the negative by soaking in water, which should be frequently changed.

Some prefer to use the hypo, quite hot, or even boiling, as thereby the size of the paper is removed, allowing of its being afterwards readily waxed.[[9]] I have always found that pouring a little boiling water upon the paper effectually accomplishes the object; some negatives will readily wax even when the size is not removed. A box iron very hot is best for the purpose; but the most important thing to attend to is that the paper should be perfectly dry, and it should therefore be passed between blotting-paper and well ironed before the wax is applied. Negatives will even attract moisture from the atmosphere, and therefore this process should at all times be resorted to immediately before the application of the wax.

Some photographers prefer, instead of using wax, to apply a solution of Canada balsam in spirits of turpentine. This certainly adds much to the transparency of the negative; and, in some instances, may be very desirable. Even in so simple a thing as white wax, there is much

variety; some forming little flocculent appearances on the paper, which is not the case with other samples. Probably it may be adulterated with stearine, and other substances producing this difference.

Before concluding these remarks, I would draw attention to the great convenience of the use of a bag of yellow calico, made so large as to entirely cover the head and shoulders, and confined round the waist by means of a stout elastic band. It was first, I believe, used by Dr. Mansell. In a recent excursion, I have, with the greatest ease, been enabled to change all my papers without any detriment whatever, and thereby dispensed with the weight of more than a single paper-holder. The bag is no inconvenience, and answers perfectly well, at any residence you may chance upon, to obstruct the light of the window, if not protected with shutters.

I would also beg to mention that a certain portion of the bromide of silver introduced into the iodized paper seems much to accelerate its power of receiving the green colour, as it undoubtedly does in the collodion. Although it does not accelerate its general action, it is decidedly a great advantage for foliage. Its best proportions I have not been able accurately to determine; but I believe if the following quantity is added to the portion of solution of iodide of silver above recommended to be made, that it will approach very near to that which will prove to be the most desirable. Dissolve separately thirty grains of bromide of potassium, and 42 grains of nitrate of silver, in separate half-ounces of distilled water; mix, stir well, and wash the precipitate; pour upon it, in a glass measure, distilled water up to one ounce; then, upon the addition of 245 grains of iodide of potassium, a clear solution will be obtained; should it not, a few more grains of the iodide of potassium will effect it. It may be well to add that I believe neither of the solutions is injured by keeping, especially if preserved in the dark.

I would here offer a caution against too great reliance being placed upon the use of gutta-percha vessels when travelling, as during the past summer I had a bottle containing distilled water which came into pieces; and I have now a new gutta-percha tray which has separated from its sides. This may appear trivial, but when away from home the greatest inconvenience results from these things, which may be easily avoided.[[10]]

Dishes of zinc painted or japanned on the interior surface answer better than gutta-percha, and one inverted within another forms, when travelling, an admirable lid-box for the protection of glass bottles, rods, &c. On the Continent wooden dishes coated with shellac varnish are almost entirely used.

Footnote 2:[(return)]

In a communication I formerly addressed to my friend the Editor of "N. & Q.," one of the arguments I used in favour of the collodion process was, that the operator was enabled at once to know the results of his attempts; and was not left in suspense concerning the probable success, as with a paper picture requiring an after development.

I made that observation not only from the partial success which had then attended my own manipulations, but from the degree of success which was attained by the majority of my photographic friends. But that objection is now almost entirely removed by the comparative certainty to which the paper process is reduced.

The effect was illustrated in two negatives of the same subject, taken at the same time, exhibited to the meeting, and which may now be seen at Mr. Bell's by those who take an interest in the subject.

For this purpose, strips of wood from 1 inch to 1½ square will be found much more convenient to pin the paper to than the tape or string usually recommended. The pressure of a corner of the paper to the wood will render it almost sufficiently adherent without the pin, and do away with the vexation of corners tearing off.

Some difference of opinion seemed to exist at the reading of the paper, as to the propriety of preparing iodized paper long before it was required for use, and I have since received some letters from very able photographers who have attributed an occasional want of success to this cause. I have, however, never myself seen good iodized paper deteriorated by age. Many friends tell me they have used it when several years old; and I can confirm this by a remarkable instance. On Tuesday (Dec. 6) I was successful in obtaining a perfectly good negative in the usual time from some paper kindly presented to me by Mr. Mackinly, and which has been in his possession since the year 1844. I should add, the paper bears the mark of "J. Whatman, 1842," and has all the characters of Turner's best photographic paper. It appears to be a make of Whatman's paper which I have not hitherto seen, and, from its date, was evidently not made for photographic purposes.

The paper may be iodized by pouring over it 30 minims of the iodizing solution, and then smoothing it over with the glass rod. Care must however be taken not to wet the back of the paper, as an unevenness of depth in the negative would probably be the result.

Much more attention should be paid to the purity of the distilled water than is generally supposed. In the many processes in which distilled water is used, there is none in which attention to this is so much required as the calotype process. I mention this from having lately had some otherwise fine negatives spoiled by being covered with spots, emanating entirely from impurities in distilled water purchased by me during a late excursion into the country.

It is very requisite that the glasses of the frames should be thoroughly cleansed before the excited papers are put into them. Although not perceptible to the eye, there is often left on the glass (if this precaution is not used) a decomposing influence which afterwards shows itself by stains upon the negative.

If boiling water is carefully poured in the negative in a porcelain dish, it will frequently remove a great deal of colouring matter, thereby rendering the negative still more translucent. It is astonishing how much colouring matter a negative so treated will give out, even when to the eye it appears so clean as not to require it.

Mr. Shadbolt suggested a remedy for the disasters referred to by Dr. Diamond with regard to the gutta-percha vessels. Gutta-percha is perfectly soluble in chloroform. Mr. Shadbolt therefore showed that if the operator carries a small bottle of chloroform with him, he would be able to mend the gutta-percha at any moment in a few seconds. It was not necessary that the bottle should hold above half an ounce of chloroform.