From Logs to Wood Flooring Part 2: Kiln Drying

Kiln Drying Logs for Wood FlooringYou saw my pine logs get milled into planks, leaving me with a big pile of wet wood (about 30% moisture content). Can’t make that into flooring. It needs to be kiln dried, and that’s the next step.

Kiln Drying Logs for Wood FlooringStickering. The material is stickered to create air spaces between the rows of planks. If this isn’t done, you’ll never get uniform drying.Stickering is more complex than just randomly adding pieces between the layers. Kiln owner Jeff Timmons says spacing of the stickers is critical to prevent the wood from twisting as it dries. Some materials, like maple, only like certain species as stickers. The wrong sticker can cause deep staining of the wet wood, leading to sticker shock when the stain is discovered. The discoloring can go so deep it’s difficult to remove, even with planing.

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Kiln Drying Logs for Wood FlooringVertical alignment of the stickers is critical to keep the pile stable. Each sticker should be directly above the sticker below.

More Character from Blue Stain. If certain species of pine sit for a while with the wood wet, the pine can develop what’s called blue stain. Some people consider this a defect, but once I learned about it I decided I wanted as much of it as possible in my floor. Normal procedure would be to sticker the wood as soon as it gets to the kiln. In my case the wood was left stacked with no air spaces between the layers of wood for about three weeks. Since the wood was wet, this encouraged the development of blue stain.

Kiln Drying Logs for Wood FlooringI REALLY like the blue stain in these boards. It’ll add a lot of character to the floor. Once the pile is stickered it can air dry for a while to reduce the time required inside the kiln.

Kiln Drying Logs for Wood FlooringThe Kiln. The kiln is like a really well insulated garage. This one can hold up to 6000 board feet of lumber.

Kiln Drying Logs for Wood FlooringThis unit provides heat and dehumidification. It maintains a temperature of about 120 degrees in the kiln, while removing the moisture that the wood is giving up. The amount of wood loaded into the kiln depends on the specie. Pine gives up its moisture at a much faster rate than oak. So if the kiln is filled to capacity with pine, the dehumidifier may not be able to keep up with the moisture coming off the wood.

Kiln Drying Logs for Wood FlooringThe plastic drape (which Jeff said is due for replacement) is used like a gasket to seal around the wood pile after it’s in the kiln. The fans don’t exhaust to the outside, they move air inside. Once the plastic is in place the fans force air to move through the pile. Jeff will monitor the lumber throughout the drying process to make sure the system is working OK.

Kiln Drying Logs for Wood FlooringAfter two weeks in the kiln my pine is down to 6%. Time to strap it down and haul it to the millwork shop for the next step. It came in wet at about 4 pounds per board foot, and leaves dry at about 1.5 pounds.

Photos By Trent Johnson

Related Video:

Logs to Flooring: Kiln Drying

Cutting Logs to Lumber

How to Plain Saw Logs into Lumber

Cutting a Log on a Bandsaw

Solar Kiln Basics

Air Drying Fresh Cut Lumber

Discussion
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7 Responses to “From Logs to Wood Flooring Part 2: Kiln Drying”
  1. Ron Grover

    Thank you George. This is a very ambitious project and I am excited for you. Looking forward to each installment of this series.

    Reply
  2. Ron Grover

    Thank you George. This is a very ambitious project and I am excited for you. Looking forward to each installment of this series.

    Reply
  3. John

    The first time I saw blue stain was working in a lumber yard (Diamond Lumber). It was in the birch veneering on interior doors. The beautiful red, white and blue was fantastic. I think I would have killed someone if I’d seen them painting this beautiful wood.

    Reply