4F10.10 Unmixing Demonstration


Entropy, laminar flow


The region between two acrylic cylinders is filled with glycerol that is then injected with a line of dye. When the inside cylinder is slowly rotated, the dye appears to be mixed. Reversing the direction of rotation of the inner cylinder makes the original dye pattern to reappear.



  • [1] Rotating cylinders with glycerol
  • [1] Red food colouring
  • [1] Green dye
  • [2] Pipette
  • [1] Pipette pump
  • [1] Glass beaker filled with water

Important Notes

  • When the pipette is immersed in glycerol, some tends to enter the pipette. You may want to prepare the pipette pump so that it can inject a slightly higher volume than that of the dye you take up.


  1. Put a drop of red food colouring into the beaker of water.
  2. Observe how the food colouring mixes quickly and irreversibly.
  3. Inject a line of dye into the glycerol using the pipette.
  4. Slowly rotate the inner cylinder and notice that the dye appears to be mixed. Do not exceed 5 full rotations.
  5. Reverse the direction of rotation until the pattern of dye reappears.


Additional Resources


  • PIRA 4F10.10


  • Don't attempt this at home!

Last revised

  • 2019


Related AV

Related demos

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.