As we enter the time of year when many of our minds around here turn to grilling and campouts, it’s time to turn to Scientific American for some valuable and timely knowledge about our favourite non-Newtonian fluid: Ketchup.
Ketchup, or Catsup if you prefer, is a shear thinning fluid – its viscosity decreases when it is under stress. This is why we often have to shake or squeeze the bottle to get it to come out… but is also why it will stay on our sandwich rather than running off immediately. So long as it’s stationary, it’s sticky!
And while we’re on the subject of non-Newtonian fluids, summertime is a good time for messy outdoor expeeriements like making another kind of non-Newtownian fluid. If you mix corn starch and water, you can make a shear thickening fluid – it is stiff under pressure but flows freely when at rest. Read about how to make your own: http://www.scifun.org/homeexpts/lumpyliquids.htm