Saturday, June 7, 2008

Reminiscences of an Active Life #5 -- June 7, 2008

Doctor Peter Henri Van Der Weyde was born in Nymegen, Holland in 1813. He went on to live a remarkable life of achievement in the sciences and the arts. He died in America in 1895.

While serving as editor of Manufacturer and Builder Magazine, he wrote many articles, including the ones which gave this blog its name. In 1893 and 1894, he published a 23-part (!) memoir in the same periodical.

Here is the fifth part. He discusses his career as a photographer.

Louis Daguerre built on the work of Joseph Nicéphore Niépce in developing photography. François Arago was an influential scientist and politician.

William Henry Fox Talbot invented the calotype, the first photographic process to use a negative to produce a positive. The Doctor criticizes him for patenting his work.

The image comes from the first installment, in the February, 1893 issue.

Part One

Part Two

Part Three

Part Four

Reminiscences of an Active Life.


From Manufacturer and Builder, Volume 25, Issue 6, June 1893

(Continued from page 99.)

4th. Career as a Photographer.-- The French government published in 1839 the description of an invention made by Daguerre, and consisting in the production of pictures of natural objects by the chemical action of the light itself, requiring no artistic training, but only mechanical manipulation guided by the judgment and knowledge of the manipulator.

As soon as I had read the description, my love for experimenting in the fields of physics and chemistry induced me to bring this invention at once to a practical test, and after some failures in the first attempts, I succeeded at last, and became soon one of the pioneers in that interesting pursuit, which was especially fascinating by reason of its novelty and the astonishing results so easily obtained.

It is not as well known as it deserves to be, that the world is indebted to Arago for the immense progress made in that invention. It was his eloquence and powerful influence which induced the French government to prevent the taking out of a patent by the inventor, and the consequent monopoly which would have resulted when this art had become private property. Arago, therefore, proposed that the government should buy the secret of the method of Daguerre’s invention by granting him a pension of several thousand francs for the rest of his life, and then publish it for the benefit of the world at large.

Arago held that so important a step in the practical application of science for the benefit of art, would, for its full development, require that the combined activity of the brains of several men should be directed in this pursuit, by making the process public property, and not smothered by patent privileges and consequent monopoly. As proof, he pointed to England, where, several years previously, Talbot had made a similar invention, intended for the same purpose, but by entirely different methods, and took out a patent for it, so as to secure for himself the exclusive benefit of its application. Arago pointed out that no progress had been made in England, where this novel art had remained perfectly stationary. He predicted that if the details of Daguerre s invention were published to all the world, scores of investigators would be induced to apply their ingenuity and make experiments to find improved methods.

The results confirmed the anticipation of the great philosopher, who had previously become known over all the world as the discoverer of many new electric phenomena, and was also the principal founder of a new magneto-electric theory. He was acknowledged as a most fascinating speaker on scientific subjects, and it was by his eloquence that he induced the government to grant to Daguerre the liberal pension referred to above. Daguerre’s previous collaborator, Niepce, died a few years before Daguerre perfected the method, of which he gave a full description, explaining the different steps of the operation, which were then at once published by the French government.

After the details of this important invention were made public, they were at once translated in the different languages of Europe and soon published in different countries. In consequence of this, many scientists began experimenting, and met with more or less success in proportion to their ability in practical manipulation. Some of them even improved upon it, and published their improvements, which again stimulated others, so that in a very few years the art was so far developed that it became possible to make it the basis of a well-paying business, which, by further improvements, has been generally prosperous, and more so now than ever before. These improvements have been continued even to the present day, and will be described later.

The original invention of Daguerre consisted in three different manipulations: first, a thin plate of silver, or silvered copper, was taken, and after cleaning the polished surface carefully with a piece of cotton wadding, Paris red, and a few drops of alcohol, it was exposed to the vapor of iodine contained in a closed box, and when it had assumed a yellow color, it was placed in the focus of a camera obscura to receive the influence of different shades of light, pertaining to the image of exterior objects; after some ten or fifteen minutes it was taken out of the camera (guarding it carefully against exposure to daylight) and placed in a box on the bottom of which was a little iron cup with mercury in it, which was then heated to the temperature of 1800 Fah., when the picture appeared.

The third step was to remove the iodine film which was easily done by immersion in a solution of common salt, or, better, of hyposulphite of soda, by which washing the picture was made permanent and could be exposed to daylight, when the image was seen to be formed by an extremely thin film of mercurial vapor, or rather by an amalgam of silver and mercury, adhering to the plate.

The first improvement made on the process of Daguerre was to make the picture more permanent, as the mercurial film could easily be rubbed out. This was accomplished by a solution of chloride of gold and hyposulphite of soda, which was poured over the plate and heated over an alcohol lamp. The second improvement was to shorten the time of exposure, which was accomplished by adding to the previous exposure of the plate over iodine, a second exposure to the vapor of bromine. Then the film, which was an iodide of silver, was changed to the double film of iodide and bromide of silver, which was so much more sensitive to light that the time was reduced from about ten minutes to a single minute or half a minute, and even less.

As Daguerre had expressed the positive opinion that the process was only adapted to produce landscapes, I confined myself to those in the beginning. I had for some time been making a collection of lenses of different kinds, such as biconvex, plano-convex, periscopic, chromatic and achromatic, and was therefore not in need of calling in the help of venders of lenses (often calling themselves opticians, without understanding the a, b, c’s of optics). As I had more than one camera obscura, it was easy enough to adapt the proper lens to one of these cameras, make a wooden frame for a plate-holder to be substituted for the ground glass, and the principal part of the apparatus was complete, as the other parts -– the iodine box and mercurial-vapor box were comparatively mere trifles.

The explanation of the interesting facts I have related is very simple indeed, when we consider the fact that sunlight has the property of decomposing certain compounds. Thus, for instance, it acts continually on the leaves of plants, where it decomposes the carbonic acid always present in the atmosphere, and which is the product of the combustion of carbon and of the animal respiration. This almost magic influence of the sunlight separates the oxygen from the carbon, setting the oxygen free, which, being a gas, is diffused in the air, while, by the circulation of the sap in plants, the carbon is deposited as woody fiber under the bark, and so the plants grow. A similar action takes place in the Daguerrean process; the influence of the light, which differs in quantity in different parts of the silver plate, decomposes the combination of the silver with the iodine, setting the volatile iodine free and leaves the silver as a fine, delicate, spongy film on the surface, which then easily absorbs the mercurial vapor, forming a delicate amalgam.

(To be Continued).

No comments: