Sadly I still can't figure out how to embed a video and more likely than not no one will watch it if its a URL so a picture will have to do!
This odd goop is called non-newtonian fluid. A newtonian fluid has a stress vs strain curve that is linear and passes through the origin, showing it has a constant viscocity. With a non-netonian fluid, it follows no such rules, and it's viscocity can change depending on stress, strain, time, or all of the above.
A simple example is this oobleck seen above. Its a simple 1-part water 2-parts cornstarch mixture. If you try to make it, eventually the stirring becomes suspiciously more difficult. This is because once it's thoroughly mixed, it is a non-newtonian fluid, and the stress caused by your stirring makes it become temporarily solid.
Infact, this corn starch mixture becomes pretty easily stressed out. When you place the mixture on a subwoofer, the vibration from the sound waves are enough to stress it out, causing it to move and solidify in strange ways, as you can see in the picture above.
Origionally I was going to make a video on how to do such, but I have no cornstarch and still need to figure out how inserting a video works, so perhaps another blog!