
Originally Posted by
pnoize2k7
to quote another forum:
Daguerrotypes (after Louis Jacques Mande Daguerre) involves photography on silvered metal plates sensitised by bromine and iodine and 'developed' by mercury vapours. The images are unique since there are no negatives or positives involved. Each photograph is unique. A daguerrotype is both negative and positive- it needs to be viewed at a certain angle to be seen as a positive. The image is really a deposition of whitish mercury on a mirror-like silver surface.
Making daguerrotypes is a very complicated and TOXIC process. The current view cameras can be used once their slides are adapted to take in copper plates. The rest is really hard to do. The copper plate is plated with silver, then buffed to a mirror-like finish.
Then it is sensitised by exposing it to bromine and iodine vapours in a fuming box. The box contains a small dish of bromine or iodine. After sensitisation, the plate is loaded into the slide and exposed. Exposures will be in the order of about 30 seconds even in bright sunlight.
After exposure, the plate is then 'developed' by placing it in a box containing a dish of mercury. The mercury is heated so that it vapourises. Its vapours will settle only on the exposed parts, and doing so produces a visible image. Ones the deposition is complete, the plate is fixed by pouring thiosulphate solution on it. Then finally, the plate is washed carefully. The mercury amalgam image is very delicate and can rub off.
The most toxic step in the process is obviously the developing part. Mercury in open containers at room temperature is already toxic... when heated it becomes even more. Remember that recent incident in a high school here which had to be closed for weeks because some mercury spilled in their science lab? Many students got sick because of this.