This idea comes to you from "The King of Random", a Youtube personality. Don't ask me how I stumbled onto his site, I can't remember. I was inspired by my youngest, who wants to be an inventor to look up cool experiments to do at home. And yes, we used potatoes to make the starch. The technical term for this is a non-newtonian liquid. An alternative fun name for it is "oobleck."
The Good: You can talk to your kids about starch and its uses. You can dig deeper for the older kids and look up the elements that compose starch, view the molecule and dig into its properties. Making starch with potatoes is a patience-building exercise, which is always a good thing. Also, hash browns for lunch was a nice change of pace. We could also talk about how the potatoes changed color over time due to oxidation. The kids loved bringing in the bottle of tonic water into the laundry room with our UV flashlight to see it glow. Scorpions also glow under UV light, by the way, which is why we have one. Summertime nights in Arizona mean hunting scorpions.
The Bad: This experiment uses a LOT of dishes, which meant a lot of cleanup. However, you can also buy potato starch if you don't want the clean up or, as he mentions, use corn starch for the same effect. The amount of starch produced by slightly less than five pounds of potatoes is really small. In fact, I poured too much tonic water and had to add corn starch to the mixture, which foiled my desire to make a second batch using tonic water and corn starch to compare the texture of the two. Drat!
The Ugly: The pan used to fry the potatoes was super ugly to clean up afterwards. I need to learn how to make hash browns without getting the potato to chemically bond to the bottom of the pan. If you have any suggestions, please put them in the comments.