Friday, October 1, 2021

Arrakis Sand Table Experiments with Glass Beads

Someone at the makerspace (thanks Sarah!) provided me with a bag of glass beads of the type used to make lines on roads reflective. I decided to see how they'd behave in Arrakis.

First experiment

For starters I tried scattering a handful of the beads over the surface of the table while it was full of baking soda. The beads are retroreflective so they don't reflect the red and blue LED lighting to your eyes when you're looking at the table. They do reflect a camera flash...

I scattered some beads on the baking soda. Without the flash on the camera, the beads just disappear.

The beads get pushed around by the ball.

After completng a pattern, then an erase, the beads are really starting to mix with the baking soda.

A completed pattern with the glass beads mixed with the baking soda.

A close up of the baking soda and glass bead mixture. You can see how rough the lines left behind by the ball look.

The different particle size/density/mass of the beads compared to the baking soda caused the ball to behave poorly when it was drawing lines. Straight and curved lines came out wobbly. I also noticed increased grinding noise with the beads. After running a few erase and drawing patterns the beads got scattered over the table a bit.

Second experiment

This time I removed the baking soda and went entirely with glass beads.

Noise level went up, line quality went down. At high speeds the beads get thrown more than the baking soda, so I had to slow the motion down to try not to clear the whole table off during a high speed erase pattern. I found that 200mm/sec was about as fast as I'd want it to go, and even then it throws the beads around.

The glass beads provide a sort of soft looking drawing.

Another view of the drawing.

With the flash, the drawing almost looks wet because of the way the flash reflects off the beads.

A soft looking drawing. There are no sharp edges to the lines because the beads are coarse and don't pile up sharply like the much finer baking soda.

The same drawing photographed with the flash. The bright spot in the center is a reflection of the flash in the glass top of the table.


The beads may be OK under certain circumstances, but I prefer the baking soda because it produces "cleaner" lines, it's quieter, and patterns can be drawn and erased faster.

The beads are denser and have larger particle size than the baking soda so they tend to get thrown more than the baking soda. That suggests that if a material with lower density and/or smaller particle size than baking soda were used, the drawings might come out even sharper, or allow higher speeds without loss of quality.

Some people use actual sand in their tables. I suspect that they might get better looking drawings (sharper, smoother lines) if they replace the heavy sand with the much lighter, finer grained baking soda.

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