>> this is making a fluid, lots of people call it ubleck and all you need is water and potatoes. >> ion't know what either of those things are. >> water or potatoes? >> no, ubleck or the nonnewton-form or whatever you said. >> they are fluids that have change in viscosity based on an increase in stress either over team or the increase in stress. >> basically this will be a solid when you move it around and you let it go and it turns into a liquid. >> right. another one you are probably more familiar with is ketchup, if you increase stress, its viscosity is lowered it's easier to tap out of the water. >> which is why you do the whole whack thing. >> there you go. ♪ >>> i'm dropping a beat. >> people who were around in the '70s know the name mavis staples, if you don't, you certainly know one of her hits. ♪ i know a place i'll take you there ♪ >> oh, yeah. ♪ let me take you there >> this is mavis back in july at the white house singing "i'll take you there." she was a big part of the civil rights movement, she was recently in phoenix at the musical instruments museum, guess what, she sa