Author: M. Ní Sídach

Oddball Gallery: 19″ Geodesic Sphere from Birch Plywood

I need to recreate this sphere concept using Transparent wood composite, which is a novel wood material which has up to 90% transparency and higher mechanical properties than natural wood. It was believed to of been fabricated for the first time in 1992 by a research group led by Professor Lars Berglund from Swedish KTH University along with a University of Maryland research group led by Professor Liangbing Hu. They developed a method to remove the color and certain chemicals from small blocks of wood, after which they were able to impregnate the resulting wood at the cellular level with polymers, such as polymethyl methacrylate and various forms of epoxy, thereby rendering the samples transparent.

As soon as news of the research results was publically released in between 2015 and 2016, see-through wood had a large press reaction, with articles in ScienceDaily, Wired, the Wall Street Journal, the New York Times, to name a few.

In actuality, those research groups had only rediscovered work originated by Siegfried Fink in 1992, a German Researcher whose work I eluded to at the start of this posting. Fink used a process very similar to Berglund’s and Hu’s to turn wood transparent in order to reveal specific cavities of the wood structure for analytical purposes rather than aesthetic and construction uses.

In either case, the idea was one of removing the light-absorbing components (mainly lignin) followed by infiltration of a polymer with a refractive index matching the wood substrate.

This is ArtScience at its ideal because transparent wood could transform architecture, artisan, and craft work by enabling novel applications and structures such as load-bearing windows. Such elements could also yield improvements in energy efficiency over glass or other traditional materials.

A three-step example of the process:

  1. The first step consists of immersing the 4 or 5-inch block of wood in a solution of water, sodium hydroxide, and sodium sulfite at boiling temperature for two hours. This enables the lignin in the cell walls to be leached out. “Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily”.
  2. The second step of oxidation with hydrogen peroxide completes the leaching of the lignin.
  3. The third step consists of immersing the material in epoxy and putting it under alternating vacuum and atmospheric pressure; this fills the wood’s natural but now disused nutrient and hydrating microscopic channels. The epoxy-filled microscopic channels create a material that has transparent refractive properties.

The length of this leeching process is primarily determined by the size and species of the wood. This semi-organic, composite material promises to have a higher strength rating than similar mono-material plastics or synthetic plastic composites, but to date remains a laboratory and experimental science, and so not ready for commercial use.

Here is the “How To” from Artisan Keith Williams of Oddball Gallery.
See the video here

According to Keith:
The math involved in most of this is way too advanced for me. Here is my “Caveman” method for figuring bevel angles. One easy way to figure the angles for any given polyhedron layout is to make a model out of 1/8” tempered hardboard. Then hot-melt glue gun to tack it all together edge-to-edge.

The glue will allow some flex, and you don’t need a bevel angle. The use a digital protractor (not an exotic tool anymore) to measure the outside angle and then bisect it for the bevel angle. This will get you close. The model will help you plan how you want to cut and assemble the pieces.

When you make the real thing, you have to have your stuff together or the glue will get the best of you. I would highly recommend starting with one of the platonic solids since all of the bevel angles will be the same.

If you are a novice, start with a beveled cube. More advanced? Try an icosahedron since all of the 20 triangles are equilateral.

If you plan to make it round, you will have to construct it with 1 1/2″ stock so you don’t sand through the vertices. The effect will be the same.

When I first started making spheres about 10 years ago I used a bandsaw and an upright belt sander.

You can use a standard lathe as long as you have the swing. The miter saw set up is not needed other than to improve accuracy and efficiency.

Keith Williams of Oddball Gallery

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