Tactile chromatography

Chromatography is a challenging concept for pupils with a vision impairment, as it relies heavily on visual observations. Here is a tactile version! Fuzzy wool balls stick to the hook (velcro) tape while smooth plastic balls drop through. This models the different interactions of molecules with a stationary phase. Instructions are further down the page.

You will need

  1. Clear acrylic pipe ~10 cm internal diameter and ~40 cm length (readily available online)
  2. Roll of adhesive hook and loop tape
  3. Photo of some smooth plastic red balls and some fluffy wool felt blue ballsWool felt balls 2 cm diameter (you need wool felt balls – fluffy pompoms won’t work)
  4. Plastic marbles (ours were replacement parts for a hungry hippos game!)
  5. Scissors

InstructionsClose-up photo of a clear acrylic pipe with strips of adhesive hook tape stuck as flaps in various places down the pipe.

  1. Cut strips of the hook tape, about 10 cm in length
  2. Fold the strips in half so the tape sticks together, leaving the ends unstuck (sideways on this will look like a T shape)
  3. Stick the tape pieces inside the plastic pipe so that the hooks are pointing up and down. You’ll need to play around with locations. Too many tape flaps and your wool balls clog up the pipe; too few and they don’t stick! We found that a spiral arrangement of the hook tape flaps worked well. You can trim the flaps and make them shorter if the wool balls are blocking the pipe.
  4. Try your model! Tip a mixture of plastic and wool balls into the top of the pipe. If it’s set up well, the plastic balls should fall straight through while the wool ones get stuck. If the wool balls are brand new and too smooth you might need to roughen the surface of them by putting them down the column a few times.