Bismuth Crystallization and Oxidation

Bismuth is a nontoxic heavy metal with a low melting point.  It can create stunning geometric crystal structures that are colored by vibrant oxidation patterns.

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Materials and Tools

  • One pound of 99.99% pure Bismuth can be purchased from Amazon for about $28 including shipping.
  •  Two metal containers such as a tuna can or coffee can
  • A propane blowtorch and igniter
  • Safety glasses, face mask, and heat-proof gloves
  • A pair of pliers to  move the container

Procedure

  1. Remove all fire hazards from the work area.
  2. Place Bismuth in the metal conatiner.
  3. Heat from above using the blowtorch.
  4. Once the bismuth has liquefied, turn off the blowtorch and use the pliers to move the container.
  5. From here you can experiment with the bismuth.  The best crystals I created were made when I coated the sides of the container with liquid bismuth.  You can also try pouring the bismuth into the other container.
  6. Allow time to cool before handling without gloves or pliers.

The bismuth can be remelted repeatedly.  My quick research on the internet suggests that after 4 or 5 remelts, the bismuth becomes too impure to create great structures.  I haven’t run into this problem.

Results

Oxidation is easy to achieve.  Crystallization not so much.  The best crystals I created were made when I coated the sides of the container with liquid bismuth.  I tried pouring the bismuth into another metal container.  I also tried pouring the bismuth onto a piece of MDF.

Documentation

I used both my phone camera and a DSLR.  The DSLR was equipped with a 10x Macro Lens which attached onto a typical zoom lens set to 25mm.  For the photosynth, I compiled a series of images into one large image.  This allowed me to see the details of a macro image within a larger context.

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Crystals on side of metal container

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Here, liquid bismuth was poured into a coffee can where it oxidized but did not crystalize.

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Oxidation did not occur on the underside of the bismuth, only on the exposed surface.

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Bismuth poured onto MDF did not oxidize or crystallize. It may have cooled too quickly.

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After cooling, bismuth was easily removed from all surfaces. It is somewhat brittle and can be broken into smaller pieces.

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Bismuth oxidized on top of the coffee can. There are some small crystals but nothing special. [click on image to see full 96 megapixel photosynth]

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I removed this crystal from the side of the container. It is 25mm in length and 13mm in width.

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Moving Forward in Digital Craft

The crystal structures have a simple, recursive geometry.  It’s fractal nature could inform how we build our parts.  At the very least, the patterns would make an interesting texture for a tooling path.

I would like to try pouring the bismuth into a small pool of water to try to build more robust crystals.