Spalted Hackberry Bowl

Spalted Hackberry Bowl

I recently made a good sized bowl with a local wood, hackberry. While hackberry isn’t a particularly interesting wood, the spalting process gave it character that a piece without spalting would never have. The process of turning spalted wood, especially a wood that is soft to begin with, was not necessarily easy or without challenges, but in the end, I think the finished piece was worth the effort.2014-09-21 19.42.29

Hackberry Characteristics

Hackberry is a common native wood in the eastern United States. In it native range, it a cheap utility wood used for mostly non-decorative purposes such as packing crates, but it also bends very well with steam treatment so it may find use in situations where curved wood is required. Some local wood turners might choose to use it for small turned objects as well. The wood is quite soft, about the same hardness as pine, so it won’t stand up to much hard use without deforming. It is soft enough to be dented or scratched with a fingernail. In appearance it closely resembles ash, and is sometimes used as an ash substitute, although anatomically it is more closely related to elm. In its native area the wood is cheap, but outside of this area it is expected to be more expensive as it is not commonly exported. Spalted pieces, however, will command a higher price because of the decorative effect achieved by the spalting process.

Spalting

Spalting refers to a fungal infection of wood which typically leaves black streaks in the wood which can be quite striking, especially against a very light wood such as hackberry or maple, another commonly spalted wood. Wood turners especially prize spalted pieces since the turning process reveals more of the spalted effect. However, spalting is a process of decay and especially in an already soft wood such as hackberry, the structural integrity of the piece may be compromised due to the spalting process.

The Material and Loss of Material

The piece I chose to turn was relatively large in my experience. It measured at least 9 inches round and was about 4 inches thick. Although the wood had been heavily waxed to slow the drying process, it still deformed in the typical manner, with water moving faster out of the end grain sections, thus compressing the non-end grain, making the round cut piece no longer round. Once the piece was back to round it was notably smaller, as would be expected, but I would ultimately loose even more material due the punky nature of significant areas of the wood due to rot and instability. Some spalted woods are stabilized to avoid these problems, but since stabilization is essentially a process of plasticizing wood, I am not overly fond of it, nor do I know if such a process can even be achieved on a bowl blank size piece of material. I have wood stabilization solutions, but by the time I realized the degree of the damage, it didn’t seem worthwhile to attempt to utilize them, especially on a piece of quite inexpensive material that I wouldn’t be devastated to lose. The difficulty in turning the rotted areas was compounded by the fact that hackberry is so soft to start with. It is difficult to achieve a nice clean cut on a soft wood and end grain tearout is exacerbated. Both of these problems were clearly present in this piece of hackberry and the spalting and rot contributed to making these characteristics even more pronounced. In the end, I would lose about 0.5 inches on the thickness and about 2 inches on the width. This amounts to about a 13% loss of thickness and about 22% width, not inconsiderable, but unavoidable in the end.

Turning Process

As would be expected for a soft wood, it was easy to cut quickly if not cleanly. But as also would be expected of a soft wood, it sanded quickly as well and a reasonably decent surface finish was obtained. The vessel walls were ultimately thinner than I had planned but it worked out. A simple wax finish was applied and buffed. The vessel is incredibly light for its size, weighing only slightly more than 10 ounces, and I think most who handle it will be expecting a much larger weight when first picking the piece up in their hands.

Outcome

Overall, I was pleased with the outcome even if the process of working with a soft and spalted wood was not without it challenges and frustrations. The spalting gives a very interesting visual appeal to an otherwise very plain and uninteresting wood. In the future, I might be inclined to stabilize at least the most affected parts of a spalted or partially rotted piece of turning material, but regardless, I will be more than willing to try working with spalted pieces in the future.