Oobleck is a word people use to describe a mixture of cornstarch and water. When you mix it in the right proportions, you form a non-Newtonian fluid. This fluid has properties of both a liquid and a solid. When it undergoes shock, it stiffens up like a solid and resists change. If you slowly press the substance it will allow your finger to sink into it like a thick liquid. If you pick up a glob of the substance it will ooze down around your hand and drip back down as though it were a think liquid.
I once saw an episode of Mythbusters where they made a large vat of this stuff. Adam was able to run across the top of it by stepping hard onto it to create a shock so the substance stiffened. I decided that I would like to do something similar to this some day. I want to make a sort of pathway of oobleck. I envision the pathway being about 6 inches deep, 5 feet long and 2 feet wide. This should be enough to allow a person to run across the top but also to sink into. I found a website online that sells 50lb bags of cornstarch for less than $20.00. I ran through some of the equations for this here:
These equations use the oobleck recipe from this website. I used the recipe of 1 part water to 1.5 parts cornstarch. It is possible I may have to mix in more starch if needed.
Platform Size: 15cm tall by 60cm wide by 152cm long
15cm * 60cm * 152cm = 136800cm^3 of total space the oobleck needs to take up
How many cups of cornstarch is in 50lbs?
WolframAlpha says there are 488 calories in 1 cup of cornstarch.
WolframAlpha also says that there are 86409 calories in 50lbs of cornstarch.
86409 calories / 488 calories = 177.1 cups of cornstarch in 1 50lb bag.
How much water do we need?
1.5x * 1x = 136800cm^3
1.5 * 2x = 136800cm^3
2.5x = 136800cm^3
x = 54720cm^3 of water needed
How much cornstarch do we need?
136800cm^3 – 54720cm^3 = 82080cm^3 of cornstarch
1 cup = 236.6cm^3 according to WolframAlpha
82080cm^3 / 236.6cm^3 = 346.91 cups of cornstarch
346.91 cups / 177.1 cups = 1.96 50lb bags of cornstarch.
According to my math (hope it’s right!) I would need just under two 50lb bags of cornstarch to build this thing. It would probably be wise to purchase a third bag as well in case there isn’t actually 50lbs of cornstarch in each bag. Also, the recipe calls for 1.5 to 2 parts of cornstarch, and two bags is barely enough to hit the minimum mark. It’s possible I will need more than that in order to get the desired effect. Hopefully I can turn this into a reality some time this year.
