Bookmatching Raised Panels - how long to acclimate

[Larry Fox]

I am working on another kitchen project and am turning my attention to the panels. Panels are average width for a kitchen and range in the 8-12" wide range. I am working in cherry and was not able to source 4/4 cherry wide enough to do the panels without a glue-up in all cases without incorporating some sap (which I am unwilling to do). For the panels that need a glue-up I was able to source some really nice 8/4 stock that I plan to resaw and bookmatch. The panels will be finished at 5/8" thick. My question is how long after resawing would you let them sit to acclimate before you glued them up for the panels? They have been sitting in my air-conditioned shop for about 2-3 weeks now in their original 8/4 form.

I am aware of the squirming around the resultant boards do after a resaw but I believe I should have no problems getting the panels I need given I only need 5/8".

Anything else I should be aware of when doing this as I would hate to turn nice 8/4 boards into sawdust?

Thanks in advance for your time.

Larry

[Scott T Smith]

Larry, in my experience the extent of movement post resawing will be related to two things. First, any differences in MC% within the board, and second any residual stresses in the lumber. I'll address the first.

8/4 boards absorb and release moisture much more slowly than 4/4 boards. When you resaw an 8/4 board and it cups, most likely there was a difference in the MC% between the shell and the core of the board, and as the core is exposed to dry air after resawing it will dry out and shrink, thus causing the cup.

As lumber dried inside a kiln, there is usually a 1-2% or so delta between the core and shell MC%'s during the drying process. At the end of the kiln cycle, most operators will "condition" the lumber, which raises the shell MC% up to match the core %. Usually the lumber leaves the kiln at 8%, or thereabouts. As it travels to the lumberyard, various parts of the stack will pick up moisture (usually the boards on the outside of the stack), so some boards will have more differences between core and shell MC% than others.

Let's say that I buy an 8/4 board from a lumberyard where it was stored in a non-climate controlled environment. Most likely the MC% will be around 12%, give or take,if this particular board has been sitting in their inventory for a few months and equalized with the environment. This is if the boards are stored vertically where air can get around them, such as in a retail environment, or if they are stored in bins in some wholesale yards. In a bulk situation where the boards are still in banded pallets, boards that you dig out of the middle of a tight stack of lumber may be more consistent in terms of MC% from shell to core.

Now, after I dig out a board at the lumberyard I take this board home and place it in my climate controlled shop, over the course of a few weeks it will slowly lose MC until it's around 7%, or thereabouts.

The very best time for me to resaw that 8/4 board is either immediately after I bring it back to my shop, or a few months later after it has acclimated inside the shop. If I resaw it a week or so after getting it home, it will probably cup, because the MC% on the outside of the board will have equalized to my shop, but the MC% within the board will still be higher. 4/4 boards are much more forgiving because they equalize much more quickly than 8/4 boards.

One good option whenever you resaw thick material is to immediately stack and sticker the boards, and place about 150 lbs per square foot on top of your stack, and give it a week or so with a gentle breeze blowing across the boards. The will still cup, but not as much and you can probably plane it out.

If you have a good moisture meter, immediately after resawing your boards check the shell MC% on each side of the board. Just stick your pins in 1/16" or so into the board, and be sure to orientate them with the grain. If you get the same reading on each side of your resawn board, odds are that it won't move cup much at all. But if you see a 1% or more delta, you'd better sticker them and get some weight on the stack for a week or two.

Hope this helps.

Scott

[Larry Fox]

Scott - this is great information and thanks a lot for the considerable amount of time that went into the reply. This stock came from Hearne Hardwoods and from their FAS+ bin - good stuff in other words. I have a tremendous amount of confidence in their ability to do things correctly so I have no reason to believe that these boards will exhibit any wierdness beyond the normal. These boards were stored horizontally in bins as opposed to vertically. I will probably play it safe and sticker with some weight in the shop for a week or so after resawing - I had originally figured some time into the schedule anyway. It will work out well anyway as I need to do a few other things next week and will be out of town on vacation the following week so if I can get them resawn this week that should be good.

[Scott T Smith]

Larry, thanks for the kind words. You won't go wrong with Hearn, Talarico, or any of the other great hardwood dealers in your state.

Do you have a good moisture meter? If so, simply check each side of the resawn board ASAP after resawing to see what kind of MC% delta there is. That in turn will give you and idea of what to expect.

Best of success to you.

Scott

[Frank Drew]

Excellent explanation, Scott, thanks for posting it. I didn't know that about aligning a moisture meter's pins with the grain; you live and learn.

[Larry Fox]

Scott - I do not have a moisture meter. It has been on the list for a while now but I have not picked one up.