Larry and Alyson Sappington share their words of wisdom for drying lumber in a dehumidification kiln:
- Be sure to sticker the lumber properly. This is a step that's very easy to shortcut by not using an adequate number of stickers, not placing stickers at the very ends of the boards, not providing a solid and providing a level base for the lumber stacks. We have learned that the quickest path to degrading lumber is improper stickering, during both the air drying process and the kiln drying process.
- Determine the maximum moisture content of your lumber that you are comfortable with before placing it into the kiln. This will vary with different kiln operations and technologies. We prefer to air dry our lumber down to a maximum of 25% before placing it into the kiln. In our experience, this seems to minimize lumber degrade during the kiln drying process.
- Monitor your kiln more than once per day. We've learned that the lumber drying process is part science/technology & part nuance. Every batch of lumber is different and even every board is different. Therefore, we visit our kiln twice per day, checking moisture content, dry bulb/wet bulb temps, condition of lumber, placement and effectiveness of baffles, and even the smell of the lumber as it's drying.
For more information about Larry & Alyson's business and the products they manufacture, please visit their Facebook page >>
iDry Vacuum Kiln
Dylan Greenquist of Genuine Timbercraft shares his words of wisdom for drying lumber in a vacuum kiln:
1. When drying wood with a moisture content over 25%, start with lower temp and use low power mode. Slowly ease temperature up until you reach 160 degrees.
2. You will often need to dry longer than one week per inch of thickness. Check the moisture content each week.
3. The kiln comes preset to discharge water every 24 hours by releasing the vacuum and opening the drain. I like to set it to 48 hours when drying walnut to keep more moisture in the chamber. This practice prevents the outer shell of the wood from becoming too dry thus trapping moisture in the center of the material.
Always begin with air drying the lumber. I have found that the longer you air dry, the better. If you are cutting material 8/4 or more, you will need to air dry at LEAST 6 months. Summertime air drying really benefits the quality of the material. It also results in less time in the kiln. I would not suggest kiln drying oak green. I have never had good luck doing this. Some of my material still air dries for 1-2 years before going into the iDry vacuum kiln.
For more information about Genuine Timbercraft, visit their webpage >>
Small-scale dehumidification kilns can be constructed as a DIY project based on the U.S. Forest Service design plan. These plans are both straight-forward and cost effective. Here's a link >>
Rocktown Urban Wood
Rocktown Urban Wood built their first solar kiln in 2019 to dry lumber for their new urban wood business. The demand for Rocktown products increased exponentially and they soon realized that a second kiln was needed! Business continues to be pretty solid and both kilns are always filled to capacity. The Rocktown crew shares words of wisdom for drying lumber in a solar kiln:
First Tip: Be patient. Very Patient. Solar Kiln Drying has been a slow process for us and we are constantly thinking of ways to speed things up. Most charges extend beyond our preconceived expectations of duration. We are tempted to pull charges out early to get other charges started. Let the charges run their full cycle and remember after the initial build costs the rest of the process essentially comes free.
Second Tip: Weigh down kiln charges. Around a year ago we started putting granite slabs on the top of our charges and we have noticed a significant improvement in the condition of the lumber at the end of the process. The weight does take up space in the kiln that could otherwise be used to dry more lumber but the benefits to the dried material far outweigh the offset of the size of the charge.
Third Tip: The baffle is integral to the production level of the kiln. We use black rubber (EPDM) roofing sheets for our baffle. It uses three different panels. One is solid from end to end and is suspended from the ceiling directly to the fan mounts. The other two are partial sheets that have been sliced like walk-in freezer doors. This allows for the sides of the baffles to extend to the floor of the kiln as well as contour to different size and shaped charges. The tight floor to ceiling and wall to wall baffle system optimizes the airflow through the charge and puts the air movement where you want it.
Also, we air dry our green lumber in a shed for an average of 4-6 months before placing the boards in the kilns.
Additional information about Rocktown Urban Wood can be found at their website >>
Both of these solar kilns are based on the Virginia Tech Solar Kiln design plan. These plans are both straight-forward and cost effective. Here's a link >>