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Titlepage of Daguerre's manual
“The process is divided into five steps.”
1. Polishing and cleaning the plate.
2. Applying the light-sensitive layer.
3. Exposing the plate to light in the camera obscura.
4. Making the latent image visible.
5. Removing the light-sensitive layer so as to prevent further development.
Step 1 | “One should begin by scrubbing the plate well.”
Polishing | 19th century engraving
Requirements: olive oil, a piece of very finely combed cotton, extremely finely ground pumice in a muslin bag, nitric acid dissolved in water (1:16), iron rack, spirit burner.
Let some pumice fall through the muslin onto the silver surface of the plate. Rub this in a circular direction with a piece of cotton soaked in olive oil. Regularly refresh the piece of cloth. Remove the oil and grit with a clean cloth. Apply the acid with a wad of cotton wool. Make sure that the acid does not fall in drips but is spread equally. The plate should assume an even film. Polish again, this time lightly.
Lay the plate on the rack, with the silver in the flame of the burner. After about five minutes the surface acquires a whitish film. Lay the plate on a cold surface and polish away just the whitish layer. Treat with acid another two times. Repeat this one more time before using the plate, followed by light polishing. Finally clean the plate well with a piece of cotton.
Step 2 | “The plate should be left in place until the silver surface is covered with a fine golden yellow veil.”
Box for vaporising iodine, 1839 | Illustration from Daguerre’s manual
Requirements: box for vaporising iodine, plate holder, cassette for the camera obscura, four metal strips, a punch and a box of pins, iodine.
Plate holder, 1839 | Illustration from Daguerre’s manual
First clamp the plate in the holder with the aid of the strips of metal. Use the punch to push the pins into the side. Spread the iodine in the basin at the bottom of the box. Cover it with muslin to equalise the vapour and at the same time to prevent it from rising in a cloud onto the plate when the cover is snapped shut. Place the cassette with the plate facing downwards on the four corners at the opening and gently close the cover.
Cassette of the camera obscura, 1839 | Illustration from Daguerre’s manual
For the following procedure there is no fixed time span, since it depends on various factors. Usually it takes between five and thirty minutes. The silver surface should be golden yellow. Make sure that it does not acquire a purple colour. In order to see this the best thing is to place the box in a space with just enough light. A room with the door ajar, for example, is suitable. Inspection of the plate should then be done quickly.
When the colour is good, the holder can be placed into the cassette that fits onto the camera obscura. Light can be provided by a candle, but avoid exposing the plate to direct light. Preferably make the exposure immediately, or otherwise within an hour.
Step 3 | “All that remains now is to open the diaphragm of the camera obscura and to consult a watch to count the minutes.”
Making the exposure in the studio | 19th century engraving
Requirements: camera obscura
Position the camera in front of an object on which a lot of light falls. Adjust the focus through the viewfinder by moving the focusing screen forwards or backwards. Place the cassette onto the camera, taking care not to dislodge it. Cover the lens and then open the doors of the cassette in the camera with the handles. Everything is now ready for the exposure. Open the lens and count the minutes.
“In Paris the exposure time varies between three and thirty minutes, in more southern countries it is shorter. The season and time of day are of considerable influence.”
Step 4 | “The impression of the image of nature exists on the plate, but it is not visible.”
Box for vaporising mercury | 19th century engraving
Requirements: at least a kilogramme of mercury, spirit burner, box for vaporising mercury, glass funnel with a long tube, box with slits.
Box for vaporising mercury, 1839 | Illustration from Daguerre’s manual
Use nothing more than a candle to illuminate the workplace during this operation. Pour the mercury with the aid of the funnel into the basin at the bottom of the box, until the bulb of the thermometer is submerged. Place the closed cassette diagonally in the box so that the plate can be seen through the little window.
Box with slits, 1839 | Illustration from Daguerre’s manual
Ignite the burner and heat the mercury to 60ºC. Then immediately remove the burner. The temperature must not rise above 75ºC. In the meantime follow the development of the image through the little window with the extremely frugal use of candlelight.
Terminate the development when the temperature falls to 45ºC. In case of overexposure one can stop at a higher temperature. Remove the plate from the holders and let it slide into the intended box. As long as the plate it stored in this, no changes take place for at least a few months, provided that one does not look at the results too often and not during the day.
Step 5 | “The mercury that draws the images is partly deposited and adheres to the silver.”
Tilted tray for rinsing the plate, 1839 | Illustration from Daguerre’s manual
Requirements: hypo (sodium thiosulphate), a tilted tray, two tinned copper tubs, a jug of distilled water, a pair of tongs.
First fill one tank with hypo and the other with tap water. Heat the water bath without allowing it to boil. Immerse the plate for a moment in the water and then transfer it to the hypo. Agitate it gently with the tongs. The yellow film on the light-sensitive layer disappears. Put the plate back into the water bath. At the same time bring the distilled water to the boil. Now lay the wet plate into the corners on the tilted tray and pour the boiling water over it. One litre is usually more than enough to rinse away the remaining salt and iodine.
The image obtained can be permanently damaged through the slightest touch. Varnishing results in the image being totally ruined. Plates should be placed behind glass and be glued down in order to preserve them; “they are furthermore unchanging, even in sunlight.”
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Hoe een daguerreotypie te maken met moderne middelen. |
