As a medium, the daguerreotype is unequaled in detail. Whereas modern film employs an emulsion of light sensitive
silver crystals to capture light, the daguerreotype's surface is solid, .999 pure silver. Photons of light act on this surface at the
molecular level to create the image. There is no "grain" to be seen and therefore the daguerreotype is much finer than any modern film.
To see what makes up the image, a scanning electron microscope must be used that can record in the millionths of an inch.
One such image
Daguerreotypes made today are made no different than in the 1840s and 1850s. The same chemicals and materials are
used as well as the many details of the process itself. The only differences now are new cameras and lenses and
modern materials used to make fuming boxes, mercury units, and other equipment. Also, a stopwatch is a lot easier
than counting "1 mississippi, 2 mississippi, etc..." for several minutes. A spot meter is very helpful too.
There are two common ways of making a daguerreotype. The most well known is that with mercury development.
The other, a recommended place to start if you are interested in producing daguerreotypes, is the Becquerel method.
The Becquerel process does not require mercury or bromine, two potentially dangerous chemicals. Also, with less equipment,
it is easier and quicker to be at the point of making images.
The Becquerel Process
Named after its discoverer,
Edmond Becquerel, the Becquerel method remains one of fascination and mystery and a convincing explanation of why it works
does not exist. A polished silver plate is sensitized with iodine vapor. After the sensitized plate is exposed to light in
a camera, the image will develop if the plate is further exposed to bright light through a red or amber filter. He called
this the action of “continuation rays.” The curious aspect is you can watch the image form much like a Polaroid.
Depending on how the subject of the image, how the plate was prepared and the development time, Becquerel images can be indistinguishable
from mercury developed plates.
The Mercury Process
In Daguerre’s original methodology
iodized plates were developed over mercury vapors. Around 1845 it was found that bromine fumes added to the iodine would increase
the sensitivity of the plate and reduce exposures from several minutes to several seconds. There was a tendency for the plates to
be bluish in high exposure areas and later it was found that an additional exposure to iodine vapors would eliminate this effect.
There are advantages and disadvantages
to both methods. Mercury developed plates are about 3 f-stops faster than Becquerel and they have less contrast, better shadow
detail and a somewhat wider exposure range. Mercury development brings with it more variables, any one of which can mess things
up. Becquerel takes a lot of work and it is not easy to get good images but is simple compared to mercury and requires less
equipment and chemicals.
There are commonalities between the two processes, namely, plate polishing, fixing, gilding, and packaging.
Some subtle differences exist in these areas but generally these steps are the same.
Easy as making bread! More examples of daguerreotype images: