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Hello William, Your second description sounds like my RAINBOW RIVERS
exhibit. It was at the Cleveland conference a few years ago. By metering the
soap solution and then starving the soap film you can control the thickness
of the solution. When the flim reaches a thickness of a tenth of a mircron
all of the colors of the rainbow  appear. I have a three page description of
this exhibit with detailed drawings of the two control handles and the
metering device. If you are planning to build a similar exhibit make sure
children are comfortable with the design of the two control functions.This
exhibit still travels with my traveling show and it is always rated first or
second most popular of the venue. If you are interested I will send you the
information. Roger Sonntag - GS&E

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