Peruvian Walnut Drying Defects
Peruvian Walnut shows wide variability, which can create drying and machining difficulties. June 13, 2014
Question (WOODWEB Member) :
We have been buying kiln dried 8/4 Peruvian walnut from a reputable wholesale outfit on the east coast (we are a commercial shop/end user). We are consistently seeing high percentages (50 to 60%) of collapse with honeycomb in adjacent areas. Also, the consistency of the material is all over the place; some stock is dense/heavy while other pieces are much lighter in weight and rather fuzzy when cut. Moisture content is typically 7 to 8% measured with a handheld meter.
Our product has an extremely high value added component so issues with material become a critical focus during operations. Often the problems donít show up until finishing when it is too late to fix. Discussions with our supplier have yielded little to no changes in outcome. They claim to be using current drying schedules from the Department of Agriculture (which I thought unusual; Iíve had prior experience drying domestic hardwoods using schedules from the Forrest Products Research Lab in WI).
We would choose to continue using this wood because of the potential for large cuttings and its attractive grain and color, but we can no longer support the costs associated with its use. Short of using a different species, is there a direction we can take to resolve our situation (they seem to be the only ones marketing this wood)?
(Commercial Kiln Drying Forum)
From Gene Wengert, forum technical advisor:
You are experiencing the issues that have been a known part of Peruvian walnut for decades. We do not know why there is such variability, but it does exist. When I worked for the US Forest Products Lab (part of the U.S. Forest Service, Dept. of Agriculture) in Madison, we worked on this "problem" (in the early 1970ís) and could not find a solution. Note that Peruvian walnut is likely to have several different species within the Juglans genus, so that can account for some variation.
Also, the schedule suggested by the US Forest Products Lab has the note "Air dry as thoroughly as possible before kiln drying." This air drying may require a year in some cases, as the water does not move out of the wood very fast. If the wood is put into the kiln too soon, the heat in the kiln will cause collapse in the wet areas (which you are seeing). In short, your supplier is probably doing the best job possible, but the species is/are troublesome, at best.
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