nous remercions Manuel et Annick Pourny pour la traduction de ce texte.

responsabilité du texte: J Roquencourt

Question à :


retour à:


To understand the contract consult the excellent: Les excellents conseils_de_Monsieur Daguerre. (Niépce)


Definition: article: Name given to the clauses and terms of a contract (Lawyers' jurisprudence Register 1827)



© Basis for a provisional treaty.

Clause 3 and clause 4 of the treaty between Niépce and Daguerre.

The physico-chemical principle of the invention.

by Jacques Roquencourt.


"I designate under the name of Héliographie the discovery that is the subject of this book. It is due to the observation of a phenomenon of light, (..)

solidifying the property, (..) which in its remarkable effects is the solution that I proposed and

which now fix my attention." (Nicéphore Niepce 1829.)


Following the proposal of Daguerre to use silver iodide as a light-sensitive layer:

"So after a few more attempts, I remained there, although regretting deeply, I confess, to have gone wrong for so long, and what is worse, if unnecessarily &&"

"But, I repeat, Sir, I do not see that we can boast to take advantage of this method, nor of those who hold to the use of metallic oxides ..."

Niépce to Daguerre: letters dated 8 November 1831 and 3 March 1832.

These comments Nicéphore confirm the following. 

The result suggested and procedures recommended by Daguerre in August 1827.

Daguerre's advice was so great that the Niépce mention in all correspondence England.

"When the mode of application in metal engraving, it is far from depreciating, but as it would be necessary to edit and dig with the chisel, he believes that this application does not succeed very imperfectly for the views, what seems much better for this kind of burning, the glass using hydrofluoric acid (vapors), he is convinced that the printing ink applied carefully to the surface corroded by acid, produce on white paper, the effect of a good test, and would again, something that would appeal to original advantage. &&& "

"and I hope to give based representations of objects of silver plated, all gradations of color from black to white, important thing that was well recommended to me by Mr Daguerre ..." Niépce Curley November 28, 1828.

Consulter les excellents conseils_de_Monsieur Daguerre. (Niépce)

Following the advice of Daguerre, Niépce wrote in 1829:

"The discovery that I made and I refer to as Heliography

is to reproduce spontaneously by the action of light, with the gradation from black to white,

the image received in the camera.

Summary: We'll specify the basis of the contract between Niépce and Daguerre and give a reminder of the articles restricting the enforcement of the contract. We'll insist on the physico-chemical principle of the discovery of heliography and give precise details about the names of the different processes. We'll prove too that the process using the residue of the Essence of Lavanda isn't the "Physautotype" , but the physiotipe.


"...hoping that I won't ask in vain the support of so many people more able than I to ensure its success..." Niépce

"...bound by the agreement which stipulates that my invention will only be made public when the required perfection has been attained, this job will be the special charge of my associate...(Mr. Daguerre)..."

(from Niépce to de Curley : on the 18th of february 1830)

"In 1829 Mr. Daguerre entered into partnership with Mr.Niépce in order to perfect Mr.Niépce's process."

(Daguerre 1839)

This discovery consists of the spontaneous reproduction of images obtained in the camera obscura.

Art.3: ...Mr.Niépce will confide to Mr.Daguerre... the principle on which is based his discovery

Art.4: ...Mr.Daguerre commits himself... to keep silent, as much about the fundamental principle of the discovery as... and to cooperate as much as he can on doing the required improvements.


What I discovered and named "heliography" consists in spontaneously bringing out the sunlit images received by the camera obscura, and this with all the shading off black into white.


Basic principle of the invention.

"Light chemically acts on the bodies either in its composed or decomposed state. Light is absorbed, combines with these elements and transmits them new properties. Thus, increasing the natural consistency of some of these bodies, it even solidifies them and makes them more or less insoluble, depending on the length and intensity of its action. This is in a few words the principle of the discovery."

The following text, which is very important and was published at the beginning of the eighteen twenties, proves that Niépce's physico-chemical principle (1) was known by the chemists.

"Comments on the solubility of resins and varnishes in alcohol. After a series of very simple tests, it's easy to convince ourselves that these substances are composed of molecules the chemical properties of which vary depending on their degree of solubility. We have to consider these substances as a compound of parts : some of which are very soluble in alcohol at low temperature or even by contact with alcohol; some other parts which are less soluble require a higher temperature; and finally some on which the action of air, sunlight or even heat of infusions leads to some modification which is put in evidence by their resistance to the action of the spirituous liquid. However these three parts constitute an homogeneous whole in the resin.

There is only the dissolution process which can show them in their real attribute. But whatever the quantity of liquid which is added to the resinous residue, it will not be possible to obtain a complete dissolution.

Thus, when we mix up too much matter with alcohol, it firstly dissolves the most soluble parts and has got very little dissolution effect on the less soluble ones. The dried parts of the resin escape from the liquid's action if we only work at moderate temperature. In this case, the varnish shows only feeble color, but if it gains in elasticity, it loses consistency and solidity. It's an advantage to combine these three qualities. We obtain such a combination by using limited amounts and by operating with much more care and slowness."

This physico-chemical principle was the basis of the treaty between Niépce and Daguerre1.

Niepce and Daguerre's research was continuously directed by this physico-chemical principle.

Colored asphalt applied on a black plate could not agree more


The initiative to provide a product photo-sensitive white.

In the instructions on the heliographic, Daguerre indicates footer this important detail and obvious:

"The lightest shade that gives this process is not white."

On February 26, 1830, so at the very beginning of the association, Daguerre wrote:

"Bitumen of Judea seems to me, and you have the necessary properties except the white ...... however we must look for the white and its opposite. Iodine does not seem appropriate, it is always iridescent or greenish. "

In the same letter, the code adds Daguerre agreed for correspondence:

52: White.

This observation made by Daguerre, the research will aim to meet these requirements.

Following an important observation of Daguerre, the two inventors in 1832 will make a discovery and develop the physautoype based on the principle of Niepce (bitumen). Subsequently, Daguerre invented the physiotype (resin).

We've already and often written that the process of residue from Essence of Lavanda is not the physautotype !

The photosensitive varnish of the physautotype is constituted with a compound of petroleum oil residue and of the residue of the Essence of Lavanda. This same residue was discovered by Daguerre. In this compound, the photosensititve part is the petroleum oil residue. Oil is classified in the family of bitumen2. The varnish constituted of different proportion of both residues being not colorated will give an image without coloration: this was what Daguerre wanted3.

After exposition to the light, the image was obtained with the successive actions of vapour of sulfuric ether and of liquid solvent, this method was developped by the diorama's director.

Daguerre discovered the sensitivity to light of the residue of the Essence of Lavanda residue.

When Niepce died, our two researchers' work was at this stage.

Then, Daguerre will bring out an image thanks to petroleum vapours and this will constitute his contributions to Niépce's process5.

(au sujet de l'utilisation des vapeurs lire: les excellents conseils_de_Daguerre.)

With the residue of oil (physautotype) there is no latent image.

Concerning the name of the process using the residue of the Essence of Lavanda, Jean-Louis Marignier, making a pretext of Daguerre's lapse of memory, attributes the invention of the process to Niépce as well. Daguerre, after Niepce's death, will mention physiotipe and not physautotype as the appellation of this process.

Daguerre wrote to Isidore:

"Physiotipe or natural print".

This comes from Phusis = nature and Typos = print.

This demonstrates that Daguerre remembered the code.

Jean-Louis Marignier's argument is not acceptable. His argument is misleading and despoils Daguerre6, and reading the correspondence demonstrates that Daguerre was not mistaken and remembered perfectly the code developed by Nicéphore Niépce. This process only belongs to Daguerre and to convince ourselves of it, we only need to read Isidore Niépce's comments on the subject in his lampoon against his "Dear Associate"4.

"As soon as Mr Daguerre was initiated into the secret of Niépce's discovery, he kept really busy about it : he replaced the bitumen of Judea used by my father by the residue from the distillation of lavender oil; there was an improvement about the whiteness of the layer which was also more sensitive to the luminous flux; but, because of the same reason, the destruction of the image was gradually brought about even in the shade and was prompt and complete if the prepared metallic plate was exposed to the light. This improvement could not have a favorable result."

See also the Law of August 7th,_1839 Law.


To sum up:


The names of the successive processes are in direct relationship with the photosensitive product used:

Heliography = Judea Bitumen = bitumen = physico-chemical principle of the treaty between Niépce and Daguerre: invented by Niépce.

Physautotype = residue of petroleum oil = bitumen residue = physico-chemical principle of the treaty between Niépce and Daguerre: invented by Niépce and Daguerre.

Physiotipe = residue of the Essence of Lavanda = resin residue = physico-chemical principle of the treaty between Niépce and Daguerre: invented by Daguerre.

Daguerréotype = silver iodide = silver salt = physico-chemical principle different from the physico-chemical principle of the treaty between Niépce and Daguerre: invented by Daguerre.


As we've already written2, the sensitivity of the varnish and the visibility of the image will only depend on the compounds which constitute the varnish.

After exposition to full daylight, the plate is dipped in a liquid solvent, the image is stripped bare, the residue which was not exposed to the daylight is dissolved.

When exposed to the vapours of petroleum oil, the image is not stripped but developed because, in this case, the molecular change (chaining of carbon atoms) of the residue, more or less exposed, will be put in evidence by the vapours of petroleum oil.

The principle is identical in the Daguerréotype: the vapours of mercury brings out, in the same way, the image according to the exposure to light of the silver iodide.


1- Since Isidore's pamphlet and the polemic cleverly carried on by the family (4), there is no choice but to accept that one doesn't know how to read a contract!

-We've already mentioned that in the annals of the "Société L J M Daguerre" published in 1989.

-See our writings contesting the different methods used to distort the truth.

2- Daguerre and optics by J.Roquencourt in Etudes photographiques n°5- 1998, notes 3 and 20 (Société française de photographie).

3- See Daguerre's comment in his opuscule on the colour of the process of Niépce. (page 39 in "edition Giroux")

4- It's possible that for Jean-Louis Marignier, Isidore can't remember either!

This pamphlet was reprinted in 1972 &endash;not for sale to the general public- with a circulation of 1000 by the company OFMI-GARAMONT*, with the contribution of André Jammes and Janine Niépce. In it, you can find the photographs of the first iris diaphragm, naturally attributed to Niépce, the chamber with bellows which is nothing but the bellows of the "Pyréolophore" as well as the "laid table" which is not by Nicéphore. (We'll get back to that point later).

Jean Dereck, by way of warning, acknowledges that "the text may suffer from a content and a tone more polemical than historical, no doubt, (he writes), but we thought it was of the greatest interest to remember the precariousness of Niépce's means and that he had his share of all kinds of traps, and thus, specifying the respective duties which the inventor respected…. If this small book somewhat contributes to the acknowledgement and fame of one of the most essential French invention, we'll have achieved our aim."

In his introduction, Jean Dereck quotes from Victor Hugo: "Loving is half way to believing" and finishes by specifying that this text has been republished as a tribute to Niepce.

Jean Dereck is dead; we would have liked to tell him how his sincerity has been deceived.

*The firm Ofmi-Garamont has changed its corporate name to Heidelberg France Company since March 31st, 1998.

5- See the summary written by Daguerre in his opuscule published by Giroux about the "Modifications made by Daguerre to Niépce's process".

6- This researcher wrote numerous articles spreading this mendacious information:

We denounce such a deception!

- We confess to not understanding this researcher: he may admire one of these inventors but why does he need to falsify texts?

- Falsification of texts with the backing of the CNRS and the Academy of Science!

- JL Marignier stands for the scientific authority of the "House of Niépce" which is guaranteed by the Academy of Science!...

We'll point out that his works, introduced as new, had already been carried out by Niépce de St Victor.

Arago when tracing the past history of the inventions of the processes of Niépce and Daguerre, points out that the use of the residue of lavender as a photosensitive element and petroleum vapours to bring out the image, are solely Daguerre's achievements.

One could be surprised that not one of the historians noticed the contradictions between JL Marignier's affirmations and all the documented sources.

Commentary by Arago, page 16, in the opuscule by Daguerre, in Giroux Edition.

"Mr Daguerre imagined a method which is named the improved Niépce Method. Firstly, he replaced bitumen by the residue from the distillation of the Essence of Lavanda, because of its better whiteness and higher sensitivity. This residue was dissolved in alcohol or ether. The liquid was then allowed to settle in a very thin and horizontal layer on the metal which left a powdery and uniform coating after evaporating. This result could not be obtained by dabbing.

After exposition of the plate (prepared as described above) in the camera obscura, Mr Daguerre put it horizontally above a recipient which contained essential oil at room temperature. In these appropriate conditions, one could appreciate at a glance that the oil vapours left intact the spherical particulates of the powdery coating which had received the action of a bright light. Vapours penetrated more or less the same area of the coating which corresponded to the halftones in the camera obscura."


Read too this copy of the Academy of Science Report.

"…because in the last ones, the varnish is only entirely removed when there are great intensity, and as the halftones are only produced by more or less thickness of varnish, it's impossible that acid reacts in the same proportion, which I've already mentioned in a Note I added to Mr Niépce's process. This drawback hasn't occurred any more since I've modified the process and replaced the bitumen by the residue of the Essence of lavender oil, and this residue dissolved in alcohol and spread on a metal or glass plate doesn't produce a continuous layer but creates on the surface a series of small spherical particulates areas of resin which leaves in between the metal bare. That's why it's possible then for an acid to etch the plate and that's what I did using fluoric acid on a glass plate with an image obtained with a camera obscura. To be able to see the result, I darkened in black the parts of the glass eaten out by the acid. But this image was very faulty because as the acid reacted on the entire surface there wasn't enough gradation of tones. This is an inconvenient which is impossible to avoid using only one acid on a plate which was not especially prepared for it. These details are by themselves sufficient to demonstrate that I worked on the etching of images and that if I didn't speak about it in the description of the modifications that I brought to Mr Niépce's process, it's because I judged the results too imperfect. "


We publish below (in french) the text changes only by the process of Daguerre and Niepce, Jean-Louis Marignier has the imprudence to call Physautotype, allowing him to attribute these improvements to the two inventors.


Napthe ou huile de pétrole blanche. (1829)


7- Après l'image latente avec le bitume de judée, avec les acides c'est maintenant avec le physautotype que J L Marignier veut nous démontrer que c'est Nicéphore le découvreur de celle-ci!

(copie d'écran du site de la maison Niépce)

With oil residue (physautotype) there is no latent image.

the image is visible, the whites are slightly gray.

Removing the residual oil or bitumen for other pure whites, Daguerre discovered the sensitivity of the residue lavender and it is only in this case, the image is often invisible.

  After the death of Niépce, it will show the image with oil vapors.

It is necessary that this residue is pure, that is not the case with the oil residue and the obtained image is visible.

"Utilisant les techniques apprises auprès de Niépce, il inventera un troisième procédé, le daguerréotype, premier

procédé photographique praticable du fait d'un temps de pose abaissé à environ quinze minutes.

Ce dernier procédé est bien entendu redevable à Niépce car bon nombre d'aspects découlent de l'héliographie. (J L Marignier)"

Rien n'est plus contraire à la vérité. (Jacques Roquencourt)

consulter: les excellents conseils_de_Daguerre.

"Using the techniques learned from Niépce, he invented a third process, the daguerreotype, the first

photographic process practicable due to an exposure time reduced to about fifteen minutes.

The latter method is obviously indebted to Niépce because many aspects arising from the engraving. (J L Marignier) "

Nothing is more contrary to the truth (Jacques Roquencourt)


"The greatest derangement of the mind is to believe things because we want them to be,

and not because we have seen that they are indeed. "Bossuet.

Text written in July 1998 and put on internet in November the 28th 2007.

références :

- premières remarques dans les annales de la Société L J M Daguerre 1989.

-** article de J B BIOT dans le Journal des Savants en mars et avril 1839.

-Daguerre et l'optique : J Roquencourt.

Études Photographiques: n°5 1998 (Société Française de Photographie).

-Note sur le portrait de M Huet : J Roquencourt, A Gunthert.

Études Photographiques: n°6 1999 (Société Française de Photographie).

- L'invention de la photographie: une tragédie (à paraître)

-JL Marignier we wrote September 26, 1990, when we questioned the presentation of his research: "you distort the results of my research in making me say the opposite of what they show in a way poutant so bright. .... for my part, I am not in the camp or in the camp Niepce Daguerre ...... I want my research and experimental results speak for themselves and their conclusions can be drawn .. (underlined in the letter) "



May unscrupulous authors respect the intellectual property and copyrights.