1. This workshop shows how a photograph is made. Visitors use a special red transparent acrylic "camera".

  2. This workshop shows how chemical reactions lead to colourful new chemical compounds.

Click to enlarge
   Description of the Experiment   
  1. The object to be photographed, a person for example, is positioned in a well-lit place. The camera is loaded with the light-sensitive paper with the lens closed. The camera is pointed as precisely as possible at the object and set solidly in position with the aid of an adjustable stand. The lens cover is removed and photograph is exposed for a suitable time, e.g. 5 seconds. The lens cover is then replaced.

    The camera is lifted onto a table with the paper side downwards. The camera turns into a developing dish when developer is poured into it. The developer is rinsed out after a minute or so. After the developer is removed, fixer is poured inside. After the fixer is added the box can be removed and after a minute the photograph is ready.

    The photograph is a negative that can be changed into a positive image if desired.

  2. The visitor will create three Heureka colours (blue, yellow, and red) simply by adding different chemicals to a basic chemical, which is ammonium iron(III) sulphate.

    The binding agent used in the workshop is casein, which is obtained from milk.

    The colours are mixed with casein to produce a paint.
   Material and Equipment   


  • a box for loading the camera with the light sensitive paper (size 50 x 50 x 50 cm)
  • a water proof camera box made from red plexi with a top that can be opened for cleaning. A 300 mm lens adjusted to the other end of the box.
  • tap water.


  • light-sensitive paper
  • developer
  • fixer

The whole workshop lasts about one hour.

  1. The idea is that the camera acts as a developing box the chemicals are poured into it. Inside the camera, there is a sheet of light-sensitive paper. The lens is opened for a suitable length of time. At the very moment of the exposure, the audience sees the actual image of the object on the paper. After the exposure, the lens is closed. A small amount of developer is poured inside the camera and the box is shaken. The same procedure is repeated with the fixer. Now, the camera can be opened and the negative image can be seen.

  2. The paints are made by mixing: a suitable binding agent is chosen and the desired colour pigment is mixed into it. The binding agent binds the paint's colour pigments and forms a film that sticks to the painting surface.
   Detailed Conclusion   
  1. ) Photography is based on a chemical reaction in which silver bromide is used. The development of the pictures is a reduction reaction in which the silver ions of the silver bromide (AgBr) are reduced to silver metal. A photograph therefore consists of a number of small silver crystals.

  2. In this workshop we first make the binding agent, for which we have chosen milk casein. The casein is denatured; i.e. it is separated from water by adding acid, e.g. vinegar, to milk. Around 30 g of casein can be obtained from one litre of milk.