How a kiln charge is dried
Boards are stacked with spacer sticks (stickers) so air can pass every face. The operator follows a schedule set for the species and thickness: heat up with high humidity, then lower the humidity in steps as the wood dries, then equalise so all boards reach a similar moisture, and finally condition with a short humid phase to relieve stresses in the surface. Sample boards in the charge are weighed or metered to decide when to move to the next step.
Drying too fast causes the defects buyers later see as cracks:
- Surface and end checks: the surface dries and shrinks before the core.
- Case hardening: locked-in stress that makes boards cup or spring when they are cut.
- Honeycombing: internal splits that may only show when a board is machined.
Kiln-dried is not the same as ISPM 15
ISPM 15 applies to wood packaging, not to furniture. Its heat treatment (HT) requires 56 °C for 30 continuous minutes through the whole profile of the wood. ISPM 15 accepts kiln drying as HT only where the schedule meets that requirement, and the packaging then still needs the official mark. A "KD" stamp on timber is a trade description, not an ISPM 15 mark.
Worked example: dried in the kiln, wet at shipping
An order for acacia dining tables specifies kiln-dried timber at 8–10% moisture content. The kiln log for the batch shows final sample boards averaging 9%. The timber then sits for several weeks in an open shed during the monsoon before machining. At the final inspection, meter readings on the finished tables are 13–14%. The kiln did its job; storage undid it. That is why buyers ask for both kiln records and a moisture check on finished goods.
How Clear To Load uses it
We do not certify kilns. During a factory audit or during-production inspection, the inspector can review kiln logs, sample-board records and timber storage. At the final inspection we take moisture content readings against your limit, 11% by default. See acacia and mango wood furniture for species-specific risks.