From Youtube Channel Veritasium:
Everyone has played with a mixture of corn starch and water (or at least I hope they have). This was one of my favorite experiments as a kid. Your hand slides into the slime easily when moving slowly but the mixture behaves as a solid if you hit it quickly. That is what is meant by ‘non-Newtonian’ – the fluid’s properties change depending on its relative motion. These properties can be exploited to dramatic effect as has been shown on speaker cones before. Here I wanted to understand what is going on, what frequencies and amplitudes work best so I used a slow-mo camera.