Troubleshooting Unexpected Honeycombing and Checks

A kiln operator seeks an explanation and some advice after a batch goes badly. January 12, 2015

Question (WOODWEB Member) :
I need someone to help me out. I will give you the details and let me know your thoughts. We stickered green red oak 8/4 in February (up in Ontario Canada) and the lumber went into our air dry yard (no t-shed or cover) until April. We then put it into our kiln. We took ten samples and they ranged from 60-80 percent moisture content. We weighed them each day for the 100 days it was in the kiln. Not one day did we lose more than 1.2 percent moisture content with most days around the .8%. Half way through the charge we even cut one of our samples which was weighing in at 35.0 percent moisture content and after doing the core test we seen it was at 42 percent and we followed that all the way down till dry. We just took the kiln out and noticed there is maybe 5-8 percent with honeycomb and or end checks.

I just donít get it. We had great sample boards with high moisture contents at the beginning. We never went over the 1.2 percent moisture loss per day and compared to the schedule in the book, we were quite reserved. When asking for 110 we were at 100 and so on. Does anyone have any insight to this? I just canít wrap my head around it. Maybe it happened in the yard with the snow and then melting snow and wind, I have no clue.

Forum Responses
(Sawing and Drying Forum)
From Contributor B:
It reads like you did well, perhaps it was an anomaly of the wood? Was this your first time drying oak in this fashion, or do you typically have success and this time it failed? Maybe that particular tree was bad wood?

From Gene Wengert, forum technical advisor:
Drying too slowly can cause checks and honeycomb. If you had checks in air drying (even in the winter) you would make them worse by running the kiln at a much higher RH than the air yard. The slow drying means high RH at the start. Also slow drying means rewetting when the fans reverse, which means checking.

From Contributor S:
I wonder if your 5% of total lumber with the defects happened to be the top layers of your stacks when they were air drying? This is the layer that would be wetted and rewetted during the initial air drying process.

From Gene Wengert, forum technical advisor:
In addition to Contributor S's comment, you also could have some pieces with bacterial infection.