"True honeycomb" defined

      What is "true honeycomb" and what causes it? November 7, 2001

What is true honeycomb?

Forum Responses
For people in the drying industry, almost all interior checking is the result of a surface or end check going deeper. Such interior checking is often called bottleneck checking in the old literature. Sometimes, it seems that bottleneck checking is restricted to surface checks (that is, not including end checks). Rarely, interior checks will not be related to a surface check and these are called true honeycomb by a few "old timers." However, within the industry that uses and cuts up wood, honeycomb refers to any interior check.

Gene Wengert, forum technical advisor

From contributor I:
I have had some interior checking in poplar that was dried in a solar kiln at 90% MC. I started the test pieces at 130 degrees with vents closed. The test pieces showed surface collapse at about 50% MC in the wood (oval depressions in the surface of 8/4, about a hand-width to 16 inches in a 12" x 8' test piece, with no surface checking). The depressions were about 1/4 to 1/2 variable. Cutting on a table saw through the center of the test piece showed literal 'honeycombing' of the wood--hollows like cross-linked long ovals. There was no end or surface checking. These pieces were sawed when fully dried--10% MC.

What creates this problem? I have had this with red gum purchased from commercial retail suppliers who buy from commercial dryers.

130 F? At this temperature, it would be nearly impossible to cause honeycomb in poplar (yellow poplar or aspen poplar). The wood must have been weakened, perhaps by a bacterial infection.

Honeycomb in red gum is common, as the wood is actually weaker and also has very poor moisture flow, so that when the sap gum is nearly dry, this wood is still quite wet and (at the higher temperatures used) cracks open.

Gene Wengert, forum technical advisor

From contributor I:
The temperature could have gone as high as 160 degrees--I could not verify it at all times. The wood was Salicaceae as far as I could tell, S. fragilis or P. tremula. The interior cracking was identical to red gum.

If P. tremula, then it most certainly is bacterial wetwood. I'll bet that the collapse was at the heartwood/sapwood zone (which is hard to see in aspen).

Gene Wengert, forum technical advisor

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