Drying Time for 2" Walnut

[Richard Amabile]

I have about 65 board feet of 2" thick black walnut that is reading a moisture content of approximately 20-23%. It has been out of the kiln for about 2 weeks and was at 12-14% when it left the kiln. The material is about 15" wide and 5 feet long. I have three questions on this:
1. If I sticker it in my shop how long would I have to keep it there to get it down to a moisture content of 6-8%?
My shop has a dehumidifier in it and I can keep the humidity at 40-50% - sometimes even a bit less. The temperature is usually 70-80 degrees during the day this time of year.
2. A second question on this that since I am short on space, will I be able to put the wood on stickers horizontially (length wise) with some stickers in between the pieces and still have it dry well? Or does it need to lay flat on stikers to dry.
3. Does anyone know of a kiln operator in the Houston Texas area that would take this wood and kiln dry it down to the 6-8% moisture level that I need.

Thanks in advance for your help.

[Scott T Smith]

I have about 65 board feet of 2" thick black walnut that is reading a moisture content of approximately 20-23%. It has been out of the kiln for about 2 weeks and was at 12-14% when it left the kiln. The material is about 15" wide and 5 feet long. I have three questions on this:
1. If I sticker it in my shop how long would I have to keep it there to get it down to a moisture content of 6-8%?
My shop has a dehumidifier in it and I can keep the humidity at 40-50% - sometimes even a bit less. The temperature is usually 70-80 degrees during the day this time of year.
2. A second question on this that since I am short on space, will I be able to put the wood on stickers horizontially (length wise) with some stickers in between the pieces and still have it dry well? Or does it need to lay flat on stikers to dry.
3. Does anyone know of a kiln operator in the Houston Texas area that would take this wood and kiln dry it down to the 6-8% moisture level that I need.

Thanks in advance for your help.

You're probably looking in the range of 6 months to drop from 20% down to 8% inside the environment that you listed. However, you should not have gained from 12% up to 20% in two weeks, even in Houston, unless it got wet or unless the core of the board had a much higher MC% than the shell when it came out of the kiln. I would advise you to try a different meter.

You can either sticker it, or lean it vertically against your walls (one layer thick), alternating the sides every few weeks to keep the warpage down. Some air movement (not too much ) will be beneficial.

Presuming that the entire board was truly at 12% two weeks ago, you should see a fairly rapid drop in MC% back down to 12% (within a few weeks), and perhaps another 4 months or so to get below 8%.

[John TenEyck]

I agree with the prior poster. If it was really 12 - 14% all the way through coming out of the kiln it is doubtful that it would climb much higher unless it got wet. Anyway, since you have a dehumidifier you can make a simple dehumidification kiln in your basement and dry the wood down to 8% in maybe 3 weeks. Lay some poly on your shop floor, then sticker the wood up off the floor on top of the poly. Then build a poly tent around it, taping all the joints. Leave a foot of clearance all around your stack of wood for air circulation. Put your dehumidifier inside and run a hose out through the tent to duct the water out to a collection bucket. You might need to set the dehumifier up on a box in order to get the water to flow out. Set your humidistat for around 70 - 80 % and plug it in. You want to take out no more than about 1% water/day. How do you know how much water that is? If you know the MC of the wood now you just calculate how much water is in by:

%MC/100 x feet^3 of wood x density of wood (lbs/ft^3) = lbs. H2O

After 24 hours weigh the water in your bucket. That will tell you how much the MC changed. If it changed more than 1% MC, turn the humidistat higher; if it changed less than 1% MC turn the humidistat lower. It's OK to dry it slower than 1% MC / day, but don't go faster (> 1% MC change) or you risk creating defects and/or internal stresses. Keep checking the MC every day and lower the humidistat every day or two as the MC stabilizes at each setting. You may also want to put a %RH meter inside the tent to verify the humidity, which is especially helpful if your dehumidifier just has a dial and no RH readout. I can't remember for sure, but I think when you get to 40% RH your wood will be at 8%. You can check Bruce Hoadley's book for a graph of %RH vs. %MC.

This really isn't very hard to do, and is the fastest way to safely dry your wood short of taking it to a pro kiln operator. Hope you find this helpful.

[Richard Amabile]

Scott/John:

Thanks very much for the information and guidance. I have ordered a new moisture meter Ligno Scanner D which I hope to have within the next few days. That should give me a much better idea of what the real moisture content is of this wood. I will post the results after I have a chance to try the new meter out.

Your thoughts on approaches and options for taking care of this wood were very helpful. I will be looking at exactly what to do next after I find out what the real moisture level turns out to be.

Thanks again to both of you?

[Neil Brooks]

Hopefully, somebody smarter than me will jump in here, but ....

I'd also think that .... before you decide on the final EMC of the boards ... you might be well advised to cut an inch off the end of one of the boards, and -- using your whiz-bang new moisture meter -- check the moisture content in the center of the board.

I think a lot of people run into trouble when they resaw a board that hasn't reached its EMC *all the way through.*

This can cause a resawn board to warp and cup in the blink of an eye.

Good luck !

[Scott T Smith]

Hopefully, somebody smarter than me will jump in here, but ....

I'd also think that .... before you decide on the final EMC of the boards ... you might be well advised to cut an inch off the end of one of the boards, and -- using your whiz-bang new moisture meter -- check the moisture content in the center of the board.

I think a lot of people run into trouble when they resaw a board that hasn't reached its EMC *all the way through.*

This can cause a resawn board to warp and cup in the blink of an eye.

Good luck !

Neil, I wouldn't claim to be "smarter" than you, but your post opens the door about discussing the use of a pin- type meter.

The proper way to check the moisture content on a board - weather using a pin type or pinless meter - is to measure on the face or the side of the board. Readings taken from the ends of the board are frequently not accurate; often times you will see a 2% or greater delta between actual MC% and that shown on the end grain.

If you're measuring a 4/4 board, then your pins should be about 3/8" long. If you're measuring an 8/4 board, then your pins should be approximately 7/8" long and insulated on the sides. If you use uninsulated pins on the thicker board, your readings will not be accurate.

[Richard Amabile]

Gentlemen:

I just received my new meter in the mail. As I said, it is a Ligno Scanner D (pinless). It reads to a depth of 3/4 inch.

I checked the 2 " walnut at the center of the board (face) and at other locations on each face of the same board. On average it is reading about 15% moisture. That is only a few % more than what it was when it came from the kiln (12-14%). I also checked the other boards and generally they are running between 14% and 15.5%. When I checked some hard maple I purchased about a year ago from a local mill and used in my table saw sled it read about 6.5%. I also checked some pine I recently used to build a bed and it read about 6%. So, I am feeling pretty confident that the meter is giving me accurate readings.
Based on this new information, my guess is that if I can keep the humidity in my shop down to 40% or below (maybe 35%) and the temperature to 70-80 degrees, I may be able to get the walnut to dry to a 6-8% level in a month or so. Does that sound right or am I expecting too much?

[Scott T Smith]

Gentlemen:

I just received my new meter in the mail. As I said, it is a Ligno Scanner D (pinless). It reads to a depth of 3/4 inch.

I checked the 2 " walnut at the center of the board (face) and at other locations on each face of the same board. On average it is reading about 15% moisture. That is only a few % more than what it was when it came from the kiln (12-14%). I also checked the other boards and generally they are running between 14% and 15.5%. When I checked some hard maple I purchased about a year ago from a local mill and used in my table saw sled it read about 6.5%. I also checked some pine I recently used to build a bed and it read about 6%. So, I am feeling pretty confident that the meter is giving me accurate readings.
Based on this new information, my guess is that if I can keep the humidity in my shop down to 40% or below (maybe 35%) and the temperature to 70-80 degrees, I may be able to get the walnut to dry to a 6-8% level in a month or so. Does that sound right or am I expecting too much?

Maybe 2 months... Sticker the boards and put some fans on them. Even better, stack and sticker them up in your attic and you may hit that one month target.

[Howard Acheson]

As a point of reference, a RH of 25% will result in an EMC of 5%. A RH of 50% will give you 9% EMC and a RH of 75% will give you 14% EMC. Temperature is not anywhere near as big a factor as relative humidity.

[Richard Amabile]

Scott:

If I stack and sticker in the attic there isn't much air flow there, but it does get hotter than the shop. I have not noticed things rusting in the attic, so I guess the humidity must control itself somehow even in the humid Houston environment. If I put it up there do I still need a fan on it? Or will simply stacking and stickering take care of it? I could put a humidity meter up there to see what the humidity is compared to the shop. I will do that and let you know what it turns out to be before I try to move everything up there.
Thanks

[Richard Amabile]

Howard:

Thanks for the info on the RH versus EMC numbers. That is good to know. I try to keep the shop at below 50% if I can. But, sometimes it is tough in Houston. I even put a second dehumidifier on today to see if I can get it lower. The first one was on max and the humidity was 49% today.

[Scott T Smith]

Richard, re attic versus shop, it's a toss up. If you can keep your RH at 40% or below, you may be better off stacking and stickering in the shop with some fans blowing over the stacks, as opposed to the attic.

The nice thing about the attic is that usually it is a lower RH%, so you have both heat and lower RH% working in your favor.