When was it first discovered and by whom?
Details of the process were made public on 19 August 1839, and Daguerre named it the Daguerreotype.
What is special about the technique?
you can only make one copy of the picture and it goes through and bounces back causes the image to be shown uside down
How does this technique work? Can you find or describe the processes needed to make it work? Maybe illustrate how it is made.
the daguerreotype method is an image which is exposed directly onto a copper sheet that's been covered with a mirror-smooth surface of silver which has in turn been coated with silver halide particles. The silver is sensitized with iodine, exposed, and then developed in mercury.
Step 1. Start with a silver-plated piece of copper and polish it to as close to a mirror finish as possible. Most daguerreotypists use a bench grinder outfitted with a polishing wheel to prepare their plates.
Step 2. The next step is to "sensitize" the plate. Place the plate into a sealed box containing a shallow tub filled with iodine crystals. After a few minutes of exposure to the iodine vapors, your silver plate should take on a purplish hue. Most "dag artists" use specially-constructed coating boxes with a sliding element at the top, allowing them to slide a plate into the vapor-filled box, then slide it out without touching the plate or exposing themselves to the vapors. Iodine vapors are extremely harmful and dangerous to work with, so precautions such as ventilators and respirators are a must.
Step 3. Mount the sensitized plate onto your camera's film holder and seal the camera.
Step 4. Pick a well-lit, stationary subject to capture. Choose something as close to totally stationary as possible, as exposure can take between 1 and 7 minutes depending on the light. Obviously, bright sunlight works best.
Step 5. In a darkroom, remove your exposed plate and tape a sheet of Amberlith film on top of it. Seal the edges with light-proof tape (both can be purchased at an art supply or photo supply store) and place it in the sun for two hours. This will develop your image, and you should start seeing results within the first 30 minutes or so. This is actually different than Louis Daguerre's original method -- he used mercury vapors to develop the image. This method is much easier, safer and less expensive.
Step 6. Now it's time to wash your plate. Mix up a Hypo clearing agent in a developing tray place the plate into the solution-filled tray. Don't let any bubbles form on the surface of the plate when you're getting it wet, otherwise your image will be ruined. Once the plate is fully submerged, gently stir the solution until your image shows on the plate as clear black and white. Follow with a water bath (using the same care in immersion) to wash away any remaining silver halide particles.
Step 7. At this point, your image is just dust on a silver plate. Touching it, brushing against it, or dropping water directly onto it will ruin it. Quickly preserve it by mounting it behind a piece of glass in a specially-constructed daguerreotype holder. You can buy an antique holder, make your own, or have one constructed by a frame shop.
Can you comment how important this technique has been for the history of photography. For example was it popular and is it still used today?
it is still used today but mostly by specialist, the dagerroetype has changed the look of photography and has enabled it to progress but it didn't last long as you could only get one copy of the photo and no extra's