The start of another school year seems a good time to mention one of
my favorite educational toys -- non-newtonian fluids. The most common of
these is "Silly Putty", however there are a variety of solutions you can make up
at home with the property that how "solid" they are depends on how hard you are
pushing on them.
These materials are not only a good discussion source for kids, you can make up games
to get them experimenting with the properties. For example, see who can stretch their glurch out into
the longest strand in a minute. (Note: kids will likely call the glurch "flubber".) Or, see who can
come up with the fastest way to get oobleck from one container to another. Pouring is slow, but
when you try to spoon it out it becomes a matter of chiseling. Its fun to watch the solid chunks
turn back to a liquid on the spoon, then back to a solid as they go back under tension when they
start to drip down.
These materials also make great slimes etc for Halloween. Put some green food coloring in
your glurch and stick some blobs of it around where it can slowly drip down
into disgusting appearances. My favorite effect is to stretch it out flat
and use it for a "lid" to a cup, then see what happens over the next few minutes.
Here are some other sources for recipes and ideas for educational plans using such materials.
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Oobleck is not a precise recipe - it is basically a thick solution of
water and corn starch - with food coloring to suite yourself. Put together
roughly equal amounts of each. If you can stir it, add more corn starch.
The thicker the solution the harder it will become to stir the solution together.
You may have to leave it to soak together. Pick it up in the spoon and you'll have chunks,
but as the tension releases you'll see them go back to liquid.
a 3:4 mixture of white glue and water (e.g. 3/4 cup of white glue to one cup of water)
Saturated water/borax. Add enough borax that it won't dissolve any more. This is approximately 3 tablespoons of Borax to 1 cup of water.
Add some food coloring (for effect only, not required to make the glurch work) to one of the two solutions then mix 3:1 of the first solution to the second.
For example, 6 tablespoons of #1 to 2 tablespoons of #2. Stir together quickly or you may get an very dense blob
in the middle. Stir/knead the glurch until it is of a uniform consistency. Or, since 3 tsp = 1 tbsp, use tablespoons to measure #1 and the same number of teaspoons to measure #2.