Segmented Bowl Disaster


One of the types of woodworking I have tried to master for a while is the art of creating, producing, and finishing Poly chromatic Bowls or Vessels. This has been extremely difficult to master, and has actually caused me one of the only injuries that I have received while woodworking.

I intend to delve into the subject of Poly Chromatic or Segmented Bowl Woodworking at length in future articles but for this article I am going to focus on how I recently ruined several months of work in a single afternoon. I had worked for about 6 months on a bowl design that I had created with my Bowl Design Software, and had decided since my earlier endeavors had been successful, to create one with intricate and complicated patterns. See my Segmented bowl below.

Destroyed Bowl

This particular bowl had hundreds of segments, each separated with contrasting wood spacers, and fashioned from six different types of wood. It was going to be a masterpiece. However, because the process had taken so long, and the pattern had become so intricate, I tried to hurry the process by taking shortcuts and modified the design on the fly. Let me explain what I mean.

I will give you a basic understanding of segmented or poly chromatic bowl creation, if you do not know much about it, at this point. I will write other articles about this in the future because this is a fascinating part of woodworking that involves creative design, cutting, sanding, gluing, and intricate lathe work.

Bowls or Vessels are assembled by cutting multiple segments from wood in mathematical shapes that form rings, which are in turn glued in stacks of concentric shapes. It sounds complicated, and it is, but the things that can be created in this way are absolutely amazing. If you want to see the work of a true master in this field, check out this bowl done by Ray Allen, that is in the Smithsonian Institute. His creations are on display there, and demonstrates the highest standards for most Poly Chromatic Bowl Designers. But to continue with this article.

Like I mentioned earlier I had worked for several months on a particularly intricate design when I decided to try to hurry the process because I was growing impatient to see the final product. I had assembled several layers and was following my software design closely to that point when I skipped a couple of identical layers deciding to make the bowl stand shorter than the original plan. By doing this I inadvertently reduced the concentric sizes of the layers which made the bowl have a staggered appearance.  Being inexperienced at segmented bowl creation, I failed to recognize what had gone wrong until I tried to define the final shape on my lathe. Because I had to remove so much material while turning, the side walls became too thin, and I broke thru the side causing holes. You can see from the above photo, that the sides of the bowl became very thin as I had to remove more and more material. As I tried to complete the shape of the bowl, my tool broke thru the surface.

Lessons learned:

  • Follow the designed plan
  • Precision of segment shapes are critical in the structure of the vessel
  • Be patient and precise

Some of the segments were so small that they were hard to sand to precise shape which resulted in the rings being slightly out of round. For those of you who have done lathe work, out of roundness requires you to remove more material. When you remove more material from a ring, the next ring glued in succession has less bonding surface and causes you to sacrifice more material from the next ring. These errors resulted in wasting a lot of precision woodwork that had to be carved away from the shape.

I have created several poly chromatic bowls in the past that are beautiful, and I have been proud of. You can see some of them that I have for sale on my etsy site. Some of these bowls involved small intricate segments but I did not get in a hurry to finish them so they are much more precise. Also this destroyed bowl was the first time I used a sled on my band saw to cut out the segments. I believe this had a lot to do with the product because tiny errors in the cut either from the drift of the blade or induced by the sled resulted in much more sanding than in the past. Normally I use my Chop Saw or Table Saw to cut out the pieces.

The design of this bowl also called for tiny sub-segments of wood between each segment that obviously varied slightly in thickness. This also caused the rings to be misshapen just slightly causing the ring to be not perfectly round. I cut these sub-segments out of hardwood rather than using thin veneer, which introduced the variance in thickness I previously mentioned. I hope the mistakes I have documented will help you to not make the same errors.

I want to thank you for reading this article. I invite you to contribute to this blog, and ask me any questions you might have about this subject or any other woodworking subject. I will try to answer all questions that I can. Poly Chromatic Vessel creation is only one of the labors of love I have with woodworking. As I stated earlier, I intend to write much more about Segmented Turning, Design, and the methods that have worked for me in the past.

Posted in Uncategorized | Leave a comment

Leave a Reply

Your email address will not be published. Required fields are marked *

The CAPTCHA cannot be displayed. This may be a configuration or server problem. You may not be able to continue. Please visit our status page for more information or to contact us.