Polymers are always fun. Especially when they are slimy.
Just prepare a 4% solution of Polyvinylalcohol (i used the one with a molecular weight of 72000) and a 4% solution of disodium tetraborate.
The PVA best dissolves under constant agitation and slight heating. Let it stir until the solution is clear and has no chunks left in it.
Then add 2 parts of the boraxsolution to 10 parts PVA-solution and stir until the consistency gets slimy.
If you want to color the slime, add the color to the PVA prior to adding the borax. A few drops of fluoresceinsolution give it a nice, shining green and quite some resemblance to Flubber.
The slime quickly dries out when stored open, so it is best keept in a glas jar or in a plastic bag. This also delays the growth of mould in/on the slime.
I have not yet tested the effect of preservative agents on the moldering.