Greenglass -

I don't see a link or attachment to your last note, so I can not see your set up, however you did refer to a flourescent light. To get fringes from the water test you should have a collimated light source. Diffuse monochromatic light (such as from a flourescent bulb) produces fringes, often referred to as "Newton's fringes", with two glass surfaces in contact.

Dick Parker