It’s a demonstration that almost has to be seen in person to believe. Otherwise, you’re likely to say, “It’s fake… there’s no way that could happen!” As you’re watching the video below, please remember that there is absolutely no trick photography. When disbelievers see the demonstration performed live, the reaction is nothing short of astonishing. Based on our past experience, we know that color mixing is not a reversible process. Mix red and blue and you make purple. Separating the colors back into their original form is not only tricky but incomprehensible for many of us. Watch the video… you’ll see why we call it a “Twist in Time.”
I believe what’s happening here is very low Reynold’s number laminar flow, which means that there are many parallel layers of “sticky” (or viscous) fluid. As the handle is turned, the dyes remain within their original layers and do not mix with each other, even as they are spread out over their individual layers. As the crank is turned backwards, the process is inverted, and since there is no fluid turbulence in laminar flow, the process can be inverted almost perfectly. You’ll find more discussion about this on our Twist in Time – Laminar Flow page in the science experiment library.