Capturing Light

Once upon a time (1232 – 1315), there was a Catalan mystic, Raymond Lull, so brilliant he was known as  Doctor Illuminatus.  Medieval mysticism being rather at a discount, he is best remembered today for having found that if you combine “oil of vitriol” (sulfuric acid) with “spirits of wine” (ethyl alcohol), you get “sweet vitriol.”  Which is completely useless unless you also know that sweet vitriol is now called “ether.”

Ether lay around as a scientific curiosity until the middle of the eighteenth century when people discovered you could get drunk inhaling the stuff.  After that, it was wildly popular and “ether frolics” became a favorite social event.  Noticing that the intoxicated revelers seemed insensitive to pain led, eventually, to its use as an anesthetic.

But ether also led down another path.  Around the same time another scientist (Schönbein) wiped up some nitric acid in his lab with a cotton cloth.  As the cloth dried, it burst into flame.  The nitric acid had reacted with the cellulose in the cotton to make a new substance, nitrocellulose.  Since nitrocellulose (guncotton) is a powerful explosive, and since humans love blowing things up almost as much as they do getting intoxicated, nitrocellulose, too, became wildly popular.  (Nitrocellulose, treated with camphor, produces celluloid, one of the earliest thermoplastics.  This was first used to make billiard balls.  These had an unfortunate tendency to explode.)

Two such popular chemicals were bound to meet one day.  When they did, the nitrocellulose dissolved in the ether and created a brand new product called collodion.  Collodion, which has a  consistency about like egg white, first found a home in everyone’s medicine chest.  Applied to a cut, it soon hardened into a tough, reasonably flexible protective shell.

But that is only half the story.

By 1834 an Englishman named William Henry Fox Talbot was completely frustrated with his bad drawing.  He longed to “capture” the scenes he saw.  But even using a camera obscura or a camera lucida (devices to project a scene onto paper for tracing) his results were mediocre.  An amateur scientist, he began to search for another method of “capturing” fleeting images.

Knowing that silver chloride darkened in sunlight, he alternately washed a piece of paper with solutions of table salt and silver nitrate.  This left him paper with silver chloride crystals embedded in the fibers.  Placing the paper in a camera obscura, he left it pointing at a building on his estate for an hour.

Et voilà!  He found, faithfully copied on his paper, an image of the oriel window from the building.

Well, not really.

He had managed to capture “fleeting reality,” but gotten it all wrong.  The darned thing was backwards.  The clear panes of glass were all dark, the dark walls light, and left and right sides were switched.

It looked just awful, but Talbot had actually made the first photographic negative.

During the following year, he discovered that he could place his backwards original in contact with a fresh piece of sensitized paper to sunlight, expose them to sunlight, and make a copy of his original.  His first process had reversed light to dark, so his copies re-reversed them to make true images.

After this brilliant initial work, Talbot temporarily abandoned the project to work on other things.  This was unfortunate because, over in France, a stage designer name Daguerre was engaged in his own experiments with the camera obscura.

The Daguerreotype system took a highly polished silvered plate and fumed it with iodine.  Next the plate, now coated with light-sensitive silver iodide, was exposed in a camera obscura.  The latent image was developed by heated mercury vapor.  Finally, washing the result with hyposulfite “fixed” the image onto the plate.

Once Talbot heard of Daguerre’s discovery, he published his own, indignantly claiming precedence and pointing out that his process was superior as a) Daguerre’s metal plate images were on the surface in extremely fragile crystals, b) they were reversed, left to right, and c) they couldn’t produce copies as his own process could.

Talbot had a fair claim and might have won the day except that he set a very high licensing fee.  Daguerre more cannily convinced the French government to purchase his rights and then give them away free to everyone.  So it was Daguerre’s process that swept the world and made him the Father of Photography.

Still, Talbot was right.  Daguerre’s images were very fragile.  Being captured on a reflective silver plate, they looked positive from one angle, negative from another, and completely absent from a third.  No matter which way you looked, though, right and left were still reversed.  Not being able to make copies was a real flaw.  And even without a license fee, silvered copper and all those chemicals made it pretty expensive.  It might have been only a temporary fad if it hadn’t been rescued by that wonderful new material collodion.

Suppose, instead of plating a piece of metal with silver and then forming light sensitive crystals on the metal surface, you were able to “paint” the surface with a transparent “paint” that would hold your photographic chemicals without reacting with them.  Suppose, in short, you had a nice, gooey, transparent liquid like collodion?

The first use of this new idea was in something called an ambrotype.  In an ambrotype you mixed some bromides and iodides into collodion.  You coated one side of a glass plate with your solution, then sensitized the coating with a silver nitrate bath.  With the coating still wet, you then exposed the plate (many looooong seconds).  Finally you developed the image, fixed it, and let it dry.

Photographers soon learned that there were two great advantages to an ambrotype.  First, being a negative image on glass, it could be used to make multiple copies.  Of course, copying was expensive, since it doubled the labor costs.   Then, too, darkroom enlargers not having been invented, the copies were almost always what we would call contact prints.  This meant that only big, expensive plates of glass gave large enough copies to satisfy those rich customers who could afford copies at all.

Then someone noticed that the actual negative images on the glass were not really black but a silvery gray.  If the glass plate was placed on a jet black background, you could see the black background through the clear areas of the plate and the image appeared as a gray picture on a black background.  In other words, without any more darkroom time, the image suddenly looked like a (fairly dark) positive image.

Of course, it was a one-shot, like a daguerreotype, and usually pretty small, but it was a true likeness of good old aunt Susie that many could afford.  As an extra added wrinkle, depending on whether the collodion side of the glass was towards or away from the black background, the right to left error could be reversed.

Last step in making photography truly “for the millions” was the invention of the tintype.  Reducing the whole process to a bare minimum, you take a piece of sheet iron and paint it black.  Then you do exactly the same as you would for an ambrotype.  Only in this case the black “background” is already in place before you put the collodion on as that coating of black paint.  Develop the negative and you have a dirt cheap (around 25¢) picture of Johnny in his brand new Civil War uniform to send home to the folks.

In time, safe celluloid film was derived from the same processes that gave birth to collodion.  George Eastman coated it with chemicals and put it in a small box for everyone, others made it into long strips to make movies and still others into multiple layers to give us colors.

But it all goes back to Talbot and his stupid, backwards oriel window.  Odd things can happen when you get it all wrong.

0 thoughts on “Capturing Light

Leave a Reply

Your email address will not be published. Required fields are marked *