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67. Silver Pictures
Have you ever wondered how photographs work? With this simple experiment, we will find out.
For this experiment, you will need:
- a key
- a saucer or plastic bowl large enough to contain the silver object
- a cardboard box large enough to cover the silver object
- Something made of silver or something silver plated. It should be something that is easy to polish, as you will have to polish it twice. Flat surfaces work much better, so a spoon or knife will work very well. The experiment will not damage the silver, but I suggest that you avoid ornate pieces with lots of hard to polish areas.
- Tincture of Iodine (with the medical supplies at your local store)
Warning! Iodine is toxic and will stain skin and clothing.
Polish the silver until it is very shiny. In a dimly lighted area, place the silver object on a saucer or in a plastic bowl. Carefully pour some iodine over the silver and then cover it with a box, to keep out as much light as possible. Wait for about two minutes.
Remove the cover and quickly place the key on a flat part of the silver. Shine a very bright light, such as a bright lamp onto the silver and the key. Hold the light there for about four minutes. Then remove the bright light and rinse the iodine from the key and the silver. Remove the key and look at the surface of the silver. You will see the image of the key.
Polishing will remove the resultant tarnish from the silver, with no harm done.
OK, so what happened. The iodine reacted with the silver to form a chemical called silver iodide. Silver iodide is sensitive to light. In bright light, it change into silver oxide, a dark colored chemical. That reaction does not happen under the key, where the light does not reach, so that part of the silve stays light colored. Together, this produces a negative image of the key.
This is basically the same thing that happens in a photograph. The parts of the film that are hit by light are changed, while the parts that remain in the dark are not. This produces a negative image. Shining a light through the negative onto treated paper produces a negative image of the negative, in other words a positive image.
Have a wonder-filled week.
