George Smith Cundell’s Calotype process.

“Meanwhile Mr. Fox Talbot, continuing to improve on his original discovery, thought fit in 1842 to make it the subject for a patent, under the name of the calotype process. In this he is accused of having incorporated the improvements of others as well as his own, a question on which we have nothing to say, except that at this stage of the invention the tracks of the numerous exploring parties run too close to each other to be clearly identified. As to the propriety of the patent itself, no one can doubt Mr. Fox Talbot's right to avail himself of it, though the results show that the policy may be questioned. For this gentleman reaped a most inadequate return, and the development of the art was materially retarded. In the execution of a process so delicate and at the best so capricious as that of photography, the experience of numbers, such as only free-trade can secure, is required to define the more or less practical methods. Mr. F. Talbot's directions, though sufficient for his own pre-instructed hand, were too vague for the tyro; and an enlistment into the ranks of the "Pilgrims of the Sun" seldom led to any result but that of disappointment. Thus, with impediments of this serious nature, photography made but slow way in England; and the first knowledge to many even of her existence came back to us from across the Border. It was in Edinburgh where the first earnest, professional practice of the art began, and the calotypes of Messrs. Hill and Adamson remain to this day the most picturesque specimens of the new discovery. It was at this crisis that a paper published in the "Philosophical Transactions" of May, 1844, by Mr. George Cundell, gave in great measure the fresh stimulus that was needed. The world was full of the praise of the daguerreotype, but Mr. Cundell stood forth as the advocate of the calotype or paper process, pointed out its greater simplicity and inexpensiveness of apparatus, its infinite superiority in the power of multiplying its productions, and then proceeded to give those careful directions for the practice, which, though containing no absolutely new element, yet suggested many a minute correction where every minutia is important.”  The words of Lady Elizabeth Eastlake in her essay titled "Photography,",

( The London Quarterly Review, No. 101, April 1857, pp. 442-468. ).

George Cundell’s process was a significant step forward in making the Calotype accessible to the Amateur photographer . He was referred to as “Most Worthy Master”by the great engineer of the day James Nasmyth. And indeed his instructions were still being cited well into the 1850s. One contemporary quoted in Humphrey’s Journal in 1856 that “ Amateurs date their success from the time Mr Cundell published. His comprehensive instructions were printed in the London , Edinburgh and Dublin Philosophical magazine in May 1844 . This was followed up in August 1846 by a paper titled “on the Gallo Nitrate of Silver” published in the same magazine.

Born in Scotland he was based in London whilst maintaining important connections in Edinburgh. He was a member of the original Edinburgh Calotype Club.

Here are the bare bones of his Calotype process.

Paper . R Turner of Chafford Mill.

Cut the paper to size. Dark room. Brush on the Silver Nitrate. 30 grains to one ounce of Distilled water. 1.94 grams. To 28.41 mill dh2o. Hang up to dry. This was double the strength suggested by Talbot. To produce silver Iodide the paper is now plunged in to a bath containing 200 grains of Potassium iodide in 1 pint of distilled water. As discovered by the London photographer Antoine Claudet 50 grains of sodium chloride were added , the resulting “chlorinated iodide of silver is infinitely more sensitive than the simple Iodide”. 12.96 grams Potassium iodide 3.24 grams sodium chloride 568 mill distilled water. This is poured in to a flat bottomed dish and the paper is floated on it for no more than a minute . *1

Hang up until "half dry".

Wash thoroughly and hang up to dry taking care not to touch the wet paper surface. *2

TO SENSITIZE Silver nitrate – 50 grains of silver nitrate in 1 ounce of distilled water.
To which is added one sixth if it’s volume of glacial acetic acid. 3.24 grams silver nitrate 4.74mill acetic acid 28.41 mill distilled water. This is Aceto Nitrate. If not required for immediate use this can be diluted or if sensitivity isn’t an issue this can be diluted to half strength. Mix a saturated solution of Gallic acid Take equal measures of this and the aceto-nitrate and float the Iodized paper on it (or brush ) As soon as the gallic nitrate is applied it should be immediately dipped in to a dish of clean water. Do not let the gallo nitrate rest on the paper for more than 5 to 10 seconds or it will embrown. Draw the paper under the surface of the water several times and then through 2 or 3 more dishes of water which of course should be perfectly clean. The paper can then be used moist or it can be hung up to dry. It should maintain its sensibility and whiteness for 24 hours. Exposure is from a few seconds to 3 or 4 minutes.

To develop mix the gallo nitrate as before and apply as before.
When the paper is thoroughly wetted it should be held in front of an iron and the image bought out by radiant heat , whilst taking care that the paper does not dry out . *3 Once the resulting image is of sufficient strength it should be transferred to a dish of clean water where it can remain until it is ready to be fixed.


Place the calotype in warm water (as hot as the finger can bare) . Change the water twice. Blot dry. Immerse in Sodium thiosulphate 1 ounce to 40 ounces of water for 2 to 3 minutes . 31 grams of sodium thiosulphate in 1136 mill of water. Wash for 12 to 24 hours depending on the thickness of the paper.

POSITIVE PAPER. Whatman Turkey Mill paper.

Salt the paper in 30 to 40 grains salt in one pint of water. Dry for use. 1.94 to 2.59 grams of salt in 568 mill of water. 0.34 to 0.46 %. Ammonio-nitrate of silver Dissolve One part of silver nitrate in twelve of distilled water. 2 grams silver nitrate in 24mill distilled water. 8.33%.
Add strong liquid ammonia until the precipitate is just dissolved. Fix as before.

​1846 Revision.

Because the sensitizer was too strong it had to be dipped in water to dilute it or the Iodized paper would embrown. A better solution was to dilute the sensitizer strength.

If required for immediate use the gallo nitrate can be diluted 10 times.

It can be diluted up to 40 times and in favourable circumstances still produce an intense picture. This extends it’s longevity but reduces it’s sensitivity.

Take 1 mill of Gallo Nitrate and add it it to 10 to 40 mill of distilled water.

*1 two to three minutes is probably better.

*2 two hours minimum the longer the better.

*3 float or brush on the gallic acid.

my own experience is that diluted 10 times it is extremely sensitive.

Interestingly in the 1850s both Marcus Sparlings and Robet Hunts manuals refer back to Cundell’s process and both misquote the original Iodizing solution.  As 17 grains of silver nitratein an ounce of distilled water and 400 grain of potassium Iodide with 100 grains of common salt
In one pint of distilled water in other words double the strength of Cundell’s original instructions.

“There is considerable latitude in the degree of dilution in which these salts may be used, and also in the manner and order of their application; but as the thickness and regularity of the coating depend upon the strength of the solution of nitrate of silver and upon the manner in which it is applied, I think it ought by all means to be applied first, before the surface of the paper is disturbed; and I am inclined to believe, that if the solution be used of double the strength suggested by Mr. Talbot, the coating will be found more perfect and continuous, and will produce better pictures. I use, accordingly, a solution of the strength of thirty grains to the ounce of distilled water”

Hunt omitted the sentence “and I am inclined to believe, that if the solution be used of double the strength suggested by Mr. Talbot, the coating will be found more perfect and continuous, and will produce better pictures.” It is possible that Sparling used Hunts manual as a source , but it must be noted that Hunt had a reputation  of trying everything before he commented on it. (Sparlings 1856 Theory and Practice of the Photographic Art , Hunts 1852 Manual of photography ).

Another possibility is that they both automatically referred back to Talbot’s original formula, noting the addition of Common salt and giving due deference to Antoine Claudet . Then of course there is the possibility that Cundell had revised his original findings to account for 1850s resources. Given Lady Eastlake comments and how often Cundell’s process is referred to ,then I don’t know what to make of this. But as Cundell says there is latitude in the strength of the Iodizer . There is only one way to find out.

In practise using Ruscombe Timothy 2 paper , the process was lightening fast , using the Gallo Nitrate sensitizer as per the 1846 revision with a pezval lens in bright sunshine with an exposure of 15 seconds there was a clear image on the paper when it was taken out of the dark slide. The sensitizer in this instance was one part aceto nitrate , one part gallic acid and 20 parts distilled water.

The full text of Cundells articles can be read here -


well worth the effort if you have time.


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