Taken from an 1840 Daguerrian
Manual Published in New York
The daguerreotype has been described as the "Mirror with a Memory" and
the process, discovered by Louis Jaques Mandé Daguerre, was first
publicly announced in January 1839 in the Gazette de France.
Its development had been aided by a partnership with Joseph Nicéphore Niepce who experimented with capturing images on pewter plates. After Niepce's death, Daguerre formed a partnership with his son, Isidore Niepce.
At around the same time, in England, Henry Fox Talbot published an account of his process for creating "Photogenic Drawings."
The daguerreotype image is made using a copper plate that has been silvered. The process is divided into 5 operations:
Polish the silver surface using cotton dipped in olive oil and covering the plate with finely powdered pumice giving a gentle rubbing action with rounded strokes. Renew the cotton and pumice frequently.
Remove the oil from the surface using clean cotton and more pumice.
Use another piece of cotton and a dilute solution of Nitric Acid (1 pint acid : 16 pints distilled water) to spread a thin and even coating of the acid over the surface. Any runs at this stage will cause a stain on the finished plate.
Sprinkle pumice on using a muslin bag and clean using more cotton.
Heat the plate, silver surface uppermost, for at least five minutes or until a strong white coating is formed on the silver.
Cool suddenly by placing the plate on a cold surface (cold stone or rock)
Polish again with pumice to remove "gummy" surface.
Repeat all above three times.
If the plate is to be stored before use then the last acid treatment should be missed. Plates could be purchased that had been processed to this stage. When the plate was needed it would be given its last acid coating.
During this process the plate could not be touched or breathed on. Before using cotton all dust had to be removed.
Coating the Plate
Fix plate silver down in a box with a reservoir of Iodine below. Fuming is to continue
until a gold colour is achieved. This is critical and can be over
(violet) or under (pale yellow) fumed. This takes between 5 mins and
1 hour depending upon the conditions (temperature).
Exposure in the Camera Giroux
Exposure times range from 3-30 minutes depending
upon light levels. This made portraits almost impossible to achieve
in the early days. Images are mostly landscapes.
Mercurial or Disengaging Process
Plate fixed into another box fitted with a thermometer, silver side
down at a 45 degree angle over a tray of Mercury (at least 3oz). Heat
is applied to the tray and the plate is warmed to 60 degrees C. (process
stops below 45-55 degrees). A viewing window allows the plate to be
observed until the image appears.
Fixing the "impression"
This can be deferred by placing the plate in a box.
Mix 1 part common salt or weak solution of Hyposulphite of pure soda (preferred to remove more Iodine) to 4 parts water in a wide mouthed vessel and filter through paper to leave a saturated salt solution. Pour this into a trough.
Fill another trough with pure water
Plunge plate into the water trough and remove to give the plate a wetting
Dip plate into salt solution (without previous wetting this solution would have an action on the image) and wash until yellow colour has gone.
Return plate to the water trough
Plate must then be placed on an angled holder and hot (not boiling) water poured over to remove the salt
Blow hard on plate to remove water.
Place plate on a board (strong paste board) and cover with glass.