Marking Klein Bottles with the Eggbot


We were lucky enough to have a visit from Cliff Stoll, geek celebrity and proprietor of Acme Klein Bottle. Acme is the finest source of Klein bottles on the internet.

Cliff came with an esoteric dilemma: how to engrave a glass Klein bottle. Acme Klein bottles are blown from borosilicate (Pyrex) glass, which has a low coefficient of thermal expansion, which means that the usual way of engraving a curved glass surface—laser engraving—doesn’t actually work.  With more common types of glass, you can use a laser engraver to etch anything you want into the surface. But with Pyrex, the surface simply melts unevenly rather than creating the microfractures that give an etched appearance.


So how would you etch the curved surface of a Klein bottle? It turns out, to our surprise, that it is remarkably easy to do it with an Ostrich Eggbot fitted with a diamond engraver attachment.

There was one complication, which is that a Klein bottle is a funny shaped object! In order to fixture the Klein bottle in the Eggbot, we made a couple of extra large couplers—much larger than the tiny pads normally used to hold the ends of an egg—with EVA foam rubber pads on their surfaces. The extra large couplers held the Klein bottle securely for rotation.



We did some initial tests with Sharpie and a medium sized Klein bottle to make sure our fixturing worked well.


And then we hooked up an engraver for a real test.


Here’s what the Klein bottle looked like after engraving. Not being particularly creative, we etched the word “KLEIN” into the side.  Because the Klein bottle is made from thick borosilicate glass, it takes engraving remarkably well. It is a much more sturdy object than the fragile Christmas ornaments that we have engraved in the past.


While we can’t imagine that it is a major market segment, the Eggbot seems to be ideal for working with Klein bottles (insomuch as anything can be perfect for working with a closed, non-orientable, boundary-free manifold). But regardless, it’s quite wonderful to find an unexpected application like this, where our little robot can solve a real-world problem that we had never even considered.

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2 thoughts on “Marking Klein Bottles with the Eggbot

  1. Unmentioned in Lenore’s post is the delightful time we had chatting & visiting! Lenore, Windell, and Zener are wonderful hosts – zillions of ideas and stories! Sure – they’re fluent with laser engravers, CNC routers, stepping motors, arduinos, and Python. But there’s way more: they appreciate the history of electronics and computing (there’s a 1000 watt, 10 ohm resistor on their bathroom wall, and a platter from a 1970 disk drive sitting right next to a watercolorbot). And all their projects – interactive LED art, Alpha clocks, LED matrix panels. Oh — the Bulbdial Shadowclock is WAY neater in person than it looks on the web.

    Much fun fooling with the Egg-Bot and a Klein-Bot. I’m surprised at the eggbot’s versatility; it works great on ellipsoids and quasi-spheres.

    If you’re traveling through Silicon Valley, make it a point to stop by for coffee or candy; It’s easy to find – just tool around the venn diagram of art, electronics, and DIY. Where all three overlap, you’ll find Zener, Windell, and Lenore.

    Warm cheers
    -Cliff (who returned to Acme in Oakland after six hours of fun)

  2. An image of a Möbius strip engraved on a Klein bottle would seem appropriate. It would be really cool to etch the cut lines that give you either one or two Möbius strips but that would require being able to draw on the (ahem) inside.

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