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When I last visited the Carnegie Science Center in Pittsburgh, I saw a really beautiful interactive fluid exhibit demonstrating the swirly, churning patterns of turbulence. The fluid was contained in a 3-foot-diameter disc, about 2 inches deep with a sturdy glass top. A large Lazy Susan bearing supported the disc so that visitors could spin it with their hands, creating a vortex in the fluid within. The effect was mesmerizing, causing folks to spend several minutes intently watching the shimmering pearlescent fluid as they rotated the disc. Upon returning home, I immediately began building a similar disc that would fit into my custom wooden coffee table. I showcased this table at Maker Faire Bay Area several times, and in this article I’ll describe how you can build your own fluid turbulence disc from readily available parts in just a few hours spread over a weekend.

Fig1 - coffee table
My custom rheoscopic table that was showcased at Maker Faire Bay Area.

[Editor’s Note: This Rheoscopic Disc Coffee Table is a project we liked so much, we’ve kept working on it — we’ve now added the video and the final steps for mounting the disc inside of the table.]

The fluid within these discs is a mixture of water, a small amount of colorant, and finely ground crystals. The crystals are microscopic, flat shiny flakes and orient themselves along the flow direction of the fluid, like logs flowing down a river. In a turbulent fluid, the flow direction is chaotic, with eddy currents and swirling causing the fluid to rapidly change direction without apparent order. Think of river rapids, where the surface is choppy and anything floating on top will be tossed about. The flat crystals track all this chaos, and their surfaces reflect light into your eyes, like the sparkling reflection of the sun on a sandy beach. In some regions of the fluid, the crystals will be oriented together so that they collectively reflect a large amount of light, and in other regions, the fluid flow will cause the crystals to face away and reflect less light. The net effect is that some regions of the fluid will appear brighter. The fluid shimmers as it churns, and is called rheoscopic — meaning “current showing.”

finished disc

The crystals are slightly more dense than water, and will settle to the bottom of the container if left undisturbed. A vigorous spin of the disc will stir up the fluid and the crystals will remain floating for 5 minutes or so. The crystals are non-toxic and easily washed away, making them an attractive additive of certain pearlescent shampoos and soaps. (In the case of these products, the density of the fluid is adjusted so that the crystals remain suspended and will not settle to the bottom.)

The vortex patterns that are formed within the disc are reminiscent of storm clouds swirling in the atmospheres of Saturn and Jupiter. (They also remind me of spiral galaxies with their twisted starry arms, however the mechanisms of their formation are slightly different. A galaxy is primarily shaped by gravity, which is the simple attraction between objects that have mass. As enormous clouds of gas and stars collide, there will be regions that are slightly denser due to the chance interaction of the clouds. Because the regions have more density, they will have a stronger gravitational pull on nearby matter, and become even denser, leading to the brighter regions of the galaxy. The exact process by which spiral galaxy arms form is still debated, but the theories are all based on the principle of gravitational attraction between huge clouds of matter over huge time scales. The brightness of the spiral arms is caused by a higher density of stars in those regions.)

Tools and parts
The parts and tools necessary to make your rheoscopic disc

Gravity does not play a big role in the patterns formed in the fluid disc. Instead, it’s the friction between the liquid molecules, which are in intimate contact with each other and the walls of the container. When a fast-moving region of fluid encounters a slower-moving region, the molecules slide past each other, and their path will meander like a person trying to make their way through a crowded room. What’s interesting is that the behavior of these sliding molecules can take one of two very distinct paths — calm or turbulent — which can be visualized in your fluid disc. Let the disc settle for a couple minutes, then start spinning it at a constant rate. You’ll notice that the fluid area near the center of the disc remains calm, and the outer area near the edge is turbulent. However, there is not a gradual transition from calm flow (called laminar flow) to turbulent flow — rather there’s a distinct transition point. This occurs because once a fluid starts to become turbulent due to very minor, random perturbations, it causes nearby fluid to also become turbulent, which spreads even more turbulence. The transition point forms where the smooth, orderly flowing of the fluid cannot resist the positive-feedback loop of perturbations that cause chaos. Note that there are no pumps inside the fluid disc — the fluid motion is caused entirely by the friction between the liquid molecules and the smooth plastic surface of the turntable and plastic disc.

Engineers have learned how to predict when a fluid will transition from laminar flow to turbulent flow based on the fluid’s viscosity, speed, and the size of the container or object that’s touching the fluid. This allows the performance of many everyday objects to be optimized. For example, the fuzzy surface of a tennis ball allows it to travel with less air resistance because the fuzz creates turbulence, which paradoxically affects the ball’s flight less than laminar flow would. The same is true for dimples on a golf ball. The size of the ball, the expected speed of travel, and the viscosity of the air all factor into producing an optimal surface pattern that can double the range of a sports ball. If you’re designing a ship, an oil pipeline, an airplane, or many other objects the encounter fluid flow, understanding the transition to turbulence is an important part of the process. The fluid disc described in this article is very similar in principle to the tools that researchers use to study fluid dynamics in the lab. It also happens to be visually entrancing — a great demonstration of the beauty of science.

Project Steps

Cut hole in turntable

Start with the Oxo turntable upside-down, and choose any of the 4 holes near the periphery. Using the hole as a starting point cut a ¾”×1½” rectangular opening with a Dremel or similar tool as shown.

IMPORTANT: Be sure to only cut through the base of the turntable, not the turntable itself.

Drill and clean up the turntable

Place the turntable right side up, and drill two 5/16″ holes spaced about 1″ apart. The edges of the holes should be 1/16″ away from the peripheral wall of the turntable.

You can position the turntable so that the drill bit plunges through the rectangular opening that you just cut, or you can let the bit hit the base after it breaks through. It’s important to drill the holes as cleanly as possible. Keep the drill bit perpendicular to the surface, and make sure it does not wander.

Use the craft knife to carefully cut away any burrs left by the drilling operation. The holes should be very smooth and neat.

Clean the interior of the disc of all dust and label residue.

Attach the acrylic disc

Apply a continuous, consistent bead of E6000 adhesive to the turntable’s rubber edge. The glue should completely cover the highest point on the edge. It helps to rotate the turntable while holding the glue tube in one place, and squeezing slowly. Apply the adhesive liberally — the mess will be hidden by later steps.

IMPORTANT: Do not substitute another adhesive without first testing its ability to make a very firm bond between the acrylic and the rubber turntable edge. A failed adhesive bond may cause a sudden, large leak.

Remove one of the protective films from the 16″ acrylic disc, and slowly lower the disc straight down onto the adhesive, keeping it centered on the turntable by eye. Apply very light pressure to seat the disc onto the rubber.

If there are any gaps in the adhesive bond, you can fix them later — do not reposition once contact with the adhesive is made! Clamping is not needed while the adhesive sets.

Inspect and touch up adhesive

After a few hours, inspect the adhesive bond for gaps or thin areas that might leak.

If you find any, you can apply more adhesive with a pencil or chopstick.

Make sure the adhesive forms a continuous seal between the disc and turntable. Messy is OK. We’ll cover it up later.

Add the liquid

You must wait at least 24 hours before filling the disc with water. If ambient temperature is cool, you should wait 48 hours to make sure the adhesive is cured.

Pour out a cup of the distilled water to make space within the jug. Shake the bottle of Pearl Swirl concentrate vigorously, then add half the bottle and a few drops of food coloring to the water jug, then invert the jug several times to mix. I used 4 drops of blue coloring for my disc.

Position the turntable upside down and rotate the base so that the rectangular opening lines up with the drilled holes. Prop up one edge of the turnable with a 1″ wood block so that the drilled holes are the highest point of the sealed space. Use the small funnel to help fill the disc from the jug. Periodically stop and gently shake the jug to keep everything mixed well.

Close it up

Keep filling until the disc is completely flooded and water spills from the holes.

Insert a well nut into each hole, then place a screw into each nut, and lightly tighten. Use a flat screwdriver to keep the well nut from spinning as you get the screw started. The screw does not need to be very tight.

Turn the disc right side up, and check for air bubbles. Eliminating all of them is very difficult, but large air bubbles can be removed by putting the disc back into the filling position, removing one well nut, and trying slightly different wood block heights to get the right angle so all air bubbles exit.

Remove protective film

With a very steady hand propped on a wood block, place the knife tip 1″ in from the edge of the disc, and spin the disc with the other hand.

Use very light pressure with the knife so the protective film is cut, but the acrylic is not harmed too much. Peel away the outer 1″ strip of protective film so only the outer edge of the acrylic is exposed. The idea is that the exposed area will be painted to cover up all of our messy glue.


Apply 2–3 light coats of spray paint to the exposed acrylic. I chose Krylon flat black.

After the paint is dry, peel away the rest of the protective film, and take your new vortex visualizer for a spin!

Mount it in a tabletop (optional)

Now mount your rheoscopic disc in a tabletop of your choice. Here we used the Kragsta table ($89) from Ikea, in black. We mounted the disc “proud,” with the acrylic floating about 1mm above the tabletop for clearance.

Set your circle drawing tool to a radius of 8″, place the needle in the existing centered hole on the bottom of the tabletop, and draw the circle. Drill a hole 3/8″ or bigger inside the circle, then insert your jigsaw blade and carefully cut out the circle.

Temporarily attach the leg supports, and mark them where the circular hole meets them. Detach the leg supports and remove 5/8″–3/4″ depth of material between your marks (should be a 16″ span), to accommodate the turntable base. Mask and spray-paint all cut edges.

Then assemble the table and set your rheoscopic disc into the tabletop. Nice!

Share it!

Here’s our completed table, which now graces the Maker Media Lab for visitors to enjoy.

Show us your table in the comments below!