Ages ago I was looking for a way to fake blood typing on the cheap, and nobody could give me a recipe.
I've finally found something that works; in the unlikely event that anyone else happens to need to do this experiment, here's the method etc. What I've done is print the method (not the technician / teacher bit) onto laminated cards with a space marked for a microscope slide with two black areas underneath it - you could do it on a black spotting tile instead, of course.
( science stuff )later Needless to say I spotted three errors AFTER laminating the cards...