Has anyone tried a magnetic sphere instead of the steel bearing on the table top with a thicker table material or with leds sandwiched between 2 layers (glass and whatever) to create a bottom lit sand table. Would the 2 magnets create too much attraction and move jerky?
I did, the magnet tries to drag instead of the bearing rolling.
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Ball or not, a magnet sphere has a north and south pole somewhere (or maybe several if weirdly polarized). That means it has a strong need to orientate in a direction and as Ryan noticed, that would prevent rolling. I suspect the ball has to be a rather soft magnetic material and I was even wondering to anneal the bearing ball on my table to improve that. But I found the hardened steel ball is good enough.
It just has to be big enough. with about 5mm distance and a 1/2"x1/2"dia magnet, I can use 1/2" and 3/8" bearing balls. But 1/4" balls sometimes get left behind. Maybe putting a conical steel pole shoe on top of the magnet might help concentrating the magnet field for smaller balls but I have not tried that as well.
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The original Zen build thread I tried a whole variety of magnets and ball sizes. I have ~8 sizes and a whole box of magnets styles and shapes. It was the hardest part of the build. What is recommended works much better than the rest. ball and magnet diameter need to be paired, a large ball won’t stick well, too small and it wanders in the magnetic field. One magnet vs stacked magnets, pole orientation, etc.
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I use one of the magnets suggested stacked on a thin magnet. That gives me a little more oomph without the issues where a stack can lose the top one or two.
If the stack doesn’t hold by itself you can glue the magnets to each other.
I’m curious if anyone has ever considered replacing the baking soda with iron filings and eliminating the ball?
AKA: Strange things I think about while housebound by the pandemic.
I’m thinking you would get lots of clumping and not many actual patterns.
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I don’t know, I have vague memories of playing with a magnet and filings in elementary school but can’t for the life of me remember the results.
I’d guess the strength and distance from the filings of the magnet would produce varying results.
You would end up with a big clump of filings above the magnet, and if any fell off as you moved around, their pattern would be random.
You could give it a try, but I’m afraid Jeff is right. Iron fillings will get dragged along.
Perhaps you remember a foil to visualise magnetic field lines, but I guess this wouldn’t be interesting to watch either… 
