Minimum Sticker Thickness

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How thin can stickers be in order to maximize kiln capacity without creating drying problems? May 11, 2005

Have there been any studies on what the minimum sticker thickness can be based on loading depth, fpm, moisture loss, operating temperature or rh%, etc? I want to maximize my kiln capacity without risking quality and/or productivity.

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
What species and thickness? What initial MC in the kiln? I do recall a study that showed that 11/16" was the thinnest possible (in a specific situation). Most kilns are designed for 3/4", so that is what is used.

From contributor D:
I posted an earlier thread about sticker thickness. I made airflow sticks at 3/4" and they dried the first load of pine with no problems. You responded to a post about electric kilns and I'd like you to clarify the part about needing "1500kW or 150kw per day average". That didn't make sense. Is it watts and kilowatts? I am using electricity for heat in one kiln, and am unsure whether to hook it my boiler, being that htg oil is going to go through the roof. Perhaps this is the year to finally build that sawdust burning boiler.

The possibility of having degrade and uneven drying made the sticker thickness question easy for me... be a little conservative and avoid the problems.

From Gene Wengert, forum technical advisor:
1 kWh = 3,413 Btu = 1 kilowatt hour.

From contributor G:
I feel if you go under 3/4" stickers, you're pushing your luck. Seems like everyone is trying to push everything to the edge. I have a friend who has 17 80,000 bdft kilns, and they use 7/8" stickers. Their family has been in business for nearly 100 years. That told me all I needed to know.

From Gene Wengert, forum technical advisor:
With 7/8" stickers, compared to 3/4", you will reduce the kiln capacity by nearly 10% (which means you have more heat and venting per BF), you will increase the volume of air between the stickers (making drying more uniform), but will slow the overall air velocity (slowing drying at MC above 30% MC), and will increase air drying in a yard that is short on space and uses piles over 6' wide. With air dried lumber, there is no benefit in using thicker stickers and in fact, there are several production losses.

From contributor G:
Do you feel that 3/4" stickers are the best way to go? I do not air dry much, and when I do, it's only in the winter. Usually my lumber, mostly red oak, comes off the mill and goes directly into the kiln. I am running DH kilns. When I air dry during the warmer months I get too much degrade and poor color. Seem to get a lot of bug damage, also.

From Gene Wengert, forum technical advisor:
Yes. You probably can improve your air yard to avoid most damage.

From contributor L:
I am in the process of building my first solar kiln. Should the stickers be same height and width (3/4" x 3/4") or does width make a difference?

From Gene Wengert, forum technical advisor:
As 3/4 x 3/4 is fairly weak, many people will go with 3/4 x 1-14 or 1-1/2.