specks. This is usually achieved by prohibiting the chemical maturity during manufacturing. During the first exposure therefore almost only internal grain specks are produced. The first development will destroy the tendency to produce internal grain specks so that after the second exposure also grain surface specks are produced. These are only produced on grains which have still no internal grain specks. The reason for this is that during the second exposure electrons emerge which are much faster caught by the stable and big internal grain specks than they can serve to build new and smaller surface grain specks. The second development in a surface developer will now attack those grains which remained unchanged by the first exposure so that an image reversal will occur. The fact that instead of a second exposure electron donating systems (e.g. chemical fogging) can be added to the second developer supports this theory. In the darkroom Careful choice of the amount of light used and the precise moment in development to provide the additional exposure gives rise to different outcomes. However, pseudo-solarization is very difficult to manage to yield consistent results. As a guide, an exposure of one second to a 25 watt incandescent lamp at two metres distance at around the end of the first minute of a 2-minute development can produce acceptable results. If the exposure is made with the developing print still in the tray of developer, it is important to stop agitation at least 10 seconds prior to exposure to allow any bubbles on the surface to disperse and to ensure that the print is lying flat. Pseudo-solarizing colour prints is more difficult because of the more careful control of temperature and timing that is required and because most amateur processing is undertaken in a processing drum rather than a dish. As lightsource also an enlarger without negative in the carrier can be used. In colour photography, different coloured lights can be used to affect pseudo-solarization, but the results become even less predictable. Using the Sabattier effect it should be obvious that it is very difficult to manage all parameters for yielding consistent and predictable results and therefore other means have been pursued such as Agfacontour and special pseudo-solarizing developers In scientific photography it was observed that when using photographic films with very high contrast (also known as lith films), the image produced by the Sabattier effect exhibited a multitude of