Gelli Baff the goo that gets kids leaping into the bath. Geli Baff, or more accurately jelly barf, this box of dyed & expandable silicone crystals is every parent’s nightmare, but every child’s dream. Basically you add the contents to a perfectly harmless bath, which is then transformed into a pond of thick & slimy goo enticing enough to get even the most reluctant child into the bath. It’s the sort of present you hope to god no-one will give your children, but you simply can’t resist giving to other people’s, because evil as the stuff is, kids just simply adore it.