The unmixing machine appears to violate time-reversal and entropy laws. The space between two concentric cylinders is filled with corn syrup, and three columns of dye are added to the syrup. When the inner cylinder is rotated the dye appears to mix, as expected, but when the inner cylinder is rotated in the opposite direction the dye appears to unmix and return to its original state. In reality, when "mixed" the dye is spread in a fine spiral sheet.
Setup: Our machine uses 11 pints of corn syrup. Apparently this also works with glycerin, but I have not tried that. The same syrup can be used several times before the dye (which does actually mix in over time) makes the syrup too dark to see the demo well. When changing the syrup it's helpful to have a second person on hand. After filling the tank one inserts the inner cylinder -- which wants to float. You need to get it aligned with the bearing on the bottom of the main tank (you can see the alignment if you look down from the top). Hold it tightly down in place, and insert the three screws. Don't over-tighten them, as it will crack the plastic housing!
We use Easter egg dye (remember to buy some when Easter rolls around!). Crush 1/4 tablet of dye into a fine powder. Put about 15 ml of corn syrup into a small beaker, add the dye, add another 15 ml of syrup, and mix well. Make 3 different colors. Let stand, ideally for a few hours or longer, to develop a richer color and for the particles to dissolve completely.
Use a rubber hose on a glass tube and suck up the colored syrup to fill the glass tube. Insert into the unmixing machine and blow into the rubber tube to push the color out. As the color comes out, pull the tube up so as to create a line. Watch the top of the colored fluid and keep its level constant as you raise the glass tube in order to distribute it evenly. As you raise the tube it will get easier and easier to blow the colored fluid out, so back off as you go! Try not to blow a bubble out the end once you're done; try stopping before the tube is completely empty.
For the actual demo, a white background is helpful for seeing the colors well.
This demo is sometimes preceded with the "ink unmixing demo" just to drive the message home and add drama to the demo: