Once upon a time cornflour was used only for making sauces like gravy thicker but I have discovered it as a fabulous ingredient for making craft activity things; so i take time out to share with parents and childcare workers (though i accept i may actual be behind on this discovery!)
You've probably all made goop before: 2 cups cornflour, 1 cup water, few drops food colouring, mix together and play. It goes solid when you touch it and runny when you don't.
But i've discovered if you add salt you get a dough that dries hard in a few days but is different from salt dough.
However if you add sugar instead you get a mixture that remains gooey like paint.
Cornflour is made up of lots of long, stringy particles that don't dissolve in water. However, they do spread themselves out, which allows the goo to act as both a solid and a liquid.