David Your request reminded me of an excercise we did in early high school (a long time ago) I don't remember all the details, but it had a satisfactory impression, perhaps you can reinvent it. I think it used dialysis tubing, dissolved starch (or sucrose) and a (starch?) indicator (iodine?). I remember a "sausage" of the dialysis tubing, filled with a test liquid, immersed in a clear jar of another liquid, perhaps with the indicator. Some of the test liquids (starch?) sat inert in the liquid, while others (with invertase?) showed a slow cascade of colour, as the (sugar?) diffused through (into the indicator?). I remember I got a particularly good result by adding honey. Good luck Kerry Clark, Apiculture Specialist B.C. Ministry of Agriculture 1201 103 Ave Dawson Creek B.C. V1G 4J2 CANADA Tel (604) 784-2225 fax (604) 784-2299 INTERNET [log in to unmask]