[WHFT, "An Account of the Processes employed in Photogenic Drawing", read before The Royal Society on 21 February 1839 and published in the Literary Gazette, no. 1153, 23 February 1839, pp. 123-124. A synopsis was also published in the Proceedings of the Royal Society, v. 4 no. 37, 21 February 1839, pp. 124-126. For a draft of WHFT's cover letter for this, see Doc. No: 03813.]
AFTER routine business, amongst which we noticed the election of Lieut. Col. Held, the author of the very interesting 'Theory of Storms,' the following letter from Mr. Fox Talbot to the secretary, was read by Mr. Christie:-
Dear Sir,- In compliance with the request of several scientific friends, who have been much interested with the. account or the art of Photogenic Drawing, which I had the honour of presenting to the Royal Society on the 31st of last month, I will endeavour to explain, as briefly I can, but at the same time without omitting anything essential, the methods which I have hitherto employed for the production of these pictures.
If this explanation, on my part, should have the effect of drawing new inquirers into the field, and if any new discoveries of importance should be the result, as I anticipate, and especially if any means should be discovered by which the sensitiveness of the paper can be materially increased, I shall be the first to rejoice at the success: and, in the meanwhile, I shall endeavour, as far as I may be able, to prosecute the inquiry myself.
The subject naturally divides itself into two heads.; viz. the preparation of the paper, and the means of fixing the design.
(1.) Preparation of the paper-.- In order to make what may be called ordinary photogenic paper, I select in the first place, paper of a good firm quality and smooth surface. I do not know that any answers better than superfine writing paper. I dip it into a weak solution of common salt, and wipe it dry, by which the salt is uniformly distributed throughout its substance. I then spread a solution of nitrate of silver on one surface only, and dry it at the fire. The solution should not be saturated, but six or eight times diluted with water. When dry, the paper is fit for use.
I have found, by experiment, that there is a certain proportion between the quantity of salt and that of the solution of silver, which answers best and gives the maximum effect. If the strength of the salt is augmented beyond this point, the effect diminishes, and, in certain cases, becomes exceedingly small.
Now, suppose we take a sheet of paper thus prepared, and wash it with a saturated solution of salt, and then dry it. We shall find (especially if the paper has been kept some weeks before the trial is made) that its sensibility is greatly diminished, and, In some cases, seems quite extinct. But it is again washed with a liberal quantity of the solution of silver, it becomes again sensible to light, and even more so than it was at first. In this way, by alternately washing the paper with salt and silver, and drying it between times, I have succeeded in increasing its sensibility to the degree that is requisite for receiving the images of the camera obscura.
In conducting this operation it will be found that the results are sometimes more and sometimes less satisfactory in consequence of small and accidental variations in the proportions employed. It happens sometimes that the chloride of silver is disposed to darken of itself, without any exposure to light: this shews that the attempt to give it sensibility has been carried too far. The object is to approach to this condition as near as possible without reaching it; so that the substance may be in a state ready to yield to the slightest extraneous force, such as the feeble impact of the violet rays when much attenuated. Having therefore prepared a number of sheets of paper with chemical proportions slightly different from one another, let a piece be cut from each, and, having been duly marked or numbered, let them be placed side by side in a very weak diffused light for about a quarter of an hour. Then, if any one of them, as frequently happens, exhibits a marked advantage over its competitors, I select the paper which bears the corresponding number to be placed in the camera obscura.
(2.) Method of fixing the images.- After having tried ammonia, and several other reagents, with very imperfect success, the first thing which gave me a successful result was the iodide of potassium, much diluted with water. If a photogenic picture is washed over with this liquid, an iodide of silver is formed which is absolutely unalterable by sunshine. This process requires precaution; for if the solution is too strong, it attacks the dark parts of the picture: It is requisite, therefore, to find by trial the proper proportions. The fixation of the pictures in this way, with proper management, is very beautiful and lasting. The specimen of lace which I exhibited to the Society, and which was made five years ago, was preserved in this manner.
But my usual method of fixing is different from this, and somewhat simpler, or at least requiring less nicety. It consists in immersing the picture in a strong solution of common salt, and then wiping off the superfluous moisture, and drying it. It is sufficiently singular that the same substance which is so useful in giving sensibility to the paper, should also be capable, under other circumstances, of destroying it; but such is, nevertheless, the fact.
Now, if the picture which has been thus washed and dried is placed in the sun, the white parts colour themselves of a pale lilac tint, after which they become insensible. Numerous experiments have shewn to me that the depth of this lilac tint varies according to the quantity of salt used, relatively to the quantity of silver. But, by properly adjusting these, the images may, If desired, be retained of an absolute whiteness. I find I have omitted to mention that those preserved by iodide are always of a very pale primrose yellow; which has the extraordinary and very remarkable property of turning to a full gaudy yellow whenever it is exposed to the heat of a fire, and recovering its former colour again when it is cold. - I am, &c.
H. FOX TALBOT
44 Queen Ann Street, Feb. 20th. 1839.
We are much pleased with the frank and ingenuous manner in which our countryman has come forward to give publicity to his process and state the results of his experiments. This is the way to promote the general benefit, and lead others into the method of pursuing similar inquiries, by which the discovery may be improved and perfected. In this c1ass we rejoice to learn that Sir John Herschel has devoted his attention to the subject, and has already, we understand, made curious progress, inasmuch as he has obtained the pictures from the light of Daniell¡¯s great galvanic battery. Sir David Brewster too, we are informed, has taken up the investigation; and when such men set to work, we may look for much to follow.
Before laying down our pen, we should mention that, at the Royal Society, Mr. Talbot shewed us the perfect picture of a riband, some three inches broad, and of a ribbed and watered pattern, taken in this manner, but not by the sun, the only active agent being the common daylight! and in a London atmosphere of the month of February too. After this, who can doubt the extreme sensibility of the prepared paper?- Ed. L. G.
[The Royal Society holds WHFT's orginal manuscript, which was faithfully transcribed in the above publication. WHFT's own draft is preserved in the Talbot Collection at the NMeM:]
to S.H.C. Esq. Secy of ye R S.
In compli w ye reqst of sev. sc. frds. who h.
kly taken an intst in been mch intered wth ye art of Ph. Drw wh I had wh ye honr of presentg to R.S. on the 31st of last mt I will endeavour to expln as briefly as I can, but at ye s. time without omitting anyng essential (really) importt to explain the method by wch I h. hitherto Employed for the productn of these drawings picts.
If this explann on my part, shd h. the effect of Drawg new enquirers into the field, & that new discvs of impce shd be the result,
is as I anticte & esply in regards if any mns shd be discd by wh the S. of the pap can be matly incrd the senty of exp. I sl be ye 1st to rejoice at ye success & In the meanwhile I intend sh. endevr as far as I may be able to proste ye enqy myself.
The subjt nat. divs itself it 2 hds the pr. of the p. Y
ye means of fixing ye design.
[illegible deletion] (1) Pn of the p.
In r to m. wt m. b. calld ordy ph. pap I
m. chse select in the 1 plcd of a pap of a gd firm qual.& smooth surface & I d. nt knw of any answg bett than superfne wr p.- I dip it into a weak soln of cn st. and wipe it dry, by wch the salt is unifly distd thrt its sce.
I then spread a sol<>sup>n of nitr. silv. on 1 surface only, & dry it at the fire. The N.S. shd note be satd but
used wth 6 or 8 times the qy of dil. w. wat.
I hfd b expt that there is a certn propn betwn the qy of salt & that of
that the soln of sil. wh answrs best & gives the max effect.
If the strth of the salt is augmd bend this point, the efft dimshes & in certn cases becomes excly small.
This paper if propy made, is very useful for all ordy photgc purposes. For ex. nothg can be m. perft than the imges it give of leaves & flowers, expecy with a summer sun; - the light passng thro' the leaves delineates every ramnificatn of their nerves.
Now suppose we take a sht of p. thus prep. was it over[overwritten] with a
In this havg ¡à prepd a no of shts of paper with
slightly difft chemical propies for each slightly difft fm 1 anther let a strip ofa piece be cust from each havg been markd or no.d - let th. be placed altogether side by side in a wk diffused day light for about [illegible deletion] ¼ an hour. Then if any one of these No as genlly freqly happs, exhibits a marked advantage over its competn I select the paper wch bears the correspg No. for to be placed in my Camera obscura.
Method of fixing the images
After havg tried ammonia & several other reagents with very imperfect success, the first thing
I met with wh gave me a succssful result, w. the iodide of p. mch dil. w. watR
If a phc picture is wsed over wth this liquid, an iodide of silver
frms itself is formed. wch is absy unalterable by sunshine. This process reqs precn. For if the soln is too stg it attacks the dark pts of the picre. It is reqste ¡à to find by trial, the propr proptns- In the The fixatn of the pictures in this way w. pr. mangt is v. beautl & lastg-
But my usual method of fixing is diff. fr this, & somewhat simpler, or a least requiring less nicety- It consists in
B bathing immersing the picture in a saturated strong soln of comn slat, & then wipe off the superfluous moisture, & [illegible overwriting] drying it.
It is suffly singular that the same
solut substce which is so useful in giving sensibly to the p. shd also be cap. under other circtces of dest' it: but such is neverless the fact.-
Now, if the picture wch has bn thus washd & dried, is
re placed in the sun the white par if the proportns the wh. parts colour themves of a pale lilac tint, after wch they become insensible- Nums expts have shown to me that the depth of this lilac tint varies accg to the quan & also accg to the other circces of the expt But by prop