I've heard of non-Newtonian liquids (and seen them on tv for entertainment value). I also hear that they keep refering to it as a material that changes its viscosity, and so turns from a liquid to a solid. However, I would never look at such a liquid and think of it in that way. What I see is simply a thick liquid that allows you to stride across it without sinking in, cause it's so thick, but the word solid doesn't come to mind. Isn't the viscosity the same all the time, just high enough that if you walk fast you'll make it across? And so can't all fluids become non-newtonian just by adding something to them to rise the viscosity to the right level?