We're exploring Oliver Wendell Holmes' 1859 story about the birth of photography. Yesterday, I looked at his description of photographic printing as an allegory for the political circumstances of his day. Today, I'm just going to look at the way he writes about chemistry. It's so vivid and precise. You get a sense for the raw materials. Holmes lends you his eyes as he peers through his magnifying glass at what's unfolding on the metal and paper.
The only thing to know before you read it is that the chemicals he's describing were relatively recent discoveries, having been isolated earlier in the 19th century. I think they may still have had a little bit of shininess, as if they were molecular gadgets. (Which they are, I suppose.)
Here is his wonderful description of how to make a daguerrotype.
A silver-plated sheet of copper is resilvered by electro-plating, and perfectly polished. It is then exposed in a glass box to the vapor of iodine until its surface turns to a golden yellow. Then it is exposed in another box to the fumes of the bromide of lime until it becomes of a blood-red tint. Then it is exposed once more, for a few seconds, to the vapor of iodine. The plate is now sensitive to light, and is of course kept from it, until, having been placed in the darkened camera, the screen is withdrawn and the camera-picture falls upon it. In strong light, and with the best instruments, three seconds' exposure is enough,‐but the time varies with circumstances. The plate is now withdrawn and exposed to the vapor of mercury at 212 degrees. Where the daylight was strongest, the sensitive coating of the plate has undertgone such a chemical change, that the mercury penetrates readily to the silver, producing a minute white granular deposit upon it, like a very thin fall of snow, drifted by the wind. The strong lights are little heaps of these granules, the middle lights thinner sheets of them; the shades are formed by the dark silver itself thinly sprinkled only, as the earth shows with a few scattered snow-flakes on its surface. The precise chemical nature of these granules we care less for than their palpable presence, which may be perfectly made out by a microscope magnifying fifty diameters or even less.
The picture thus formed would soon fade under the action of light, in consequence of further changes in the chemical elements of the film of which it consists. Some of these elements are therefore removed by washing it with a solution of hyposulphite of soda, after which it is rinsed with pure water. It is now permanent in the light, but a touch wipes off the picture as it does the bloom from a plum. To fix it, a solution of hyposulphite of soda containing chloride of gold is poured on the plate while this is held over a spirit-lamp. It is then again rinsed with pure water, and is ready for its frame.
Read the rest of Holmes' "The Stereoscope and the Stereograph."
Revisit more pieces from The Atlantic's archives with the Technology Channel.
Image: John Hanson.
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