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Viscosity Estimation

Make the flow show.


The FlowShow      is a gadget enabling you to estimate the viscosity levels of fluids using the senses mother nature provided. Get your educated guess without special equipment and calculations, as you need for conventional methods (like ball drop experiments). Best of all, it can be done directly in a flask or a bottle.

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Let’s start with the basics. Viscosity is the fluid’s resistance against the flow, measured in Pascal seconds (Paּ s). The seven vials within the FlowShow have viscosities between 1/1000 Pa s (usually expressed as one milli-Pascal second or mPa s) up to 1000 Pa s. With a ratio between min and max of one million, they cover viscosity levels over six orders of magnitude.

How can you use your eyes to use the FlowShow as a poor’s men viscometer? Well, first of all, we need to create flow.

1st experiment: Panta Rhei

Keep the FlowShow in a horizontal position until all the fluids are leveled. Flip the FlowShow into a vertical position and watch how gravity will make it flow.

Were your eyes fast enough to see a difference between the three lowest viscosities in the vials? Everything happens within less than a second. At higher viscosity levels, the transition is nicely visible for us humans. Even in a slow-motion shot, spotting the difference between water-like and two-order or 100x times more viscous fluid is difficult.

The friction is low, and the fluids oscillate back and forth until the actuation energy is dissipated into heat. At 1 Pas, the internal friction becomes significant.

The highest viscosity of 1000 Pa s requires more than an hour to level out completely.

2nd experiment: Shaken, not stirred.

We can use bubbles inside the vials to distinguish the three low viscosities. To form bubbles, shake the FlowShow as hard as you can. Can you hear the noise the low viscous samples make?

The shaking draws surrounding air into the fluids. The high shear rate (20 s⁻¹ to 2000 s⁻¹) disperses the air into tiny bubbles. The bubbles’ buoyancy depends on their size and the velocity at which they rise. Try to look at bubbles with similar sizes between the three vials. The longer the bubbles are inside the fluid, the higher the viscosity.

In addition to sight and hearing, you can also rely on your touch. Shake the fluid gently and compare the haptic feedback. A sloshing liquid has a viscosity lower than 1 Pa s. You can do the same experiments with your fluid directly in the container and compare it to what you learned from the FlowShow.

Reach out to our team at to get a FlowShow for yourself.

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