Questions about equilibrating KD SYP

[Gary Ragatz]

I don’t have much experience drying wood – I usually just buy kiln-dried hardwood from my local guy, sticker it for a week or two to let it acclimate to the shop and then go to work. Recently, I ordered some 2x4 and 2x6 SYP from Menards, for a new workbench. When I brought it home, the moisture content was higher than I was expecting (ranged from 15% to 20%, using my cheap meter), but apparently that is where it was supposed to be – it’s graded KD19.

I cut it to rough length and stickered it in the basement (where the bench will live) and put a fan nearby on low, just to keep some air moving. The basement is ~64* and the relative humidity is ~35%. The wood has been there for 10 days, and my meter now says it’s at ~10%.

A couple of questions:



Does it seem reasonable that the MC has come down that much in 10 days (I’ve never dealt with wood as wet as this before)? I’m testing the wood on the ends that I cut the day I picked up the lumber, so I’m wondering if I’m getting an artificially low reading because the ends are drying out faster than the rest. I’ve tried testing on the side grain in the middle of a board (again, around 10%), but I can’t get the pins on my meter to penetrate very far, so I’m not sure if I’m getting valid readings there. I can make some fresh cuts if that would yield a more accurate reading.
I have some other SYP that's been in the basement for a few months, and it's at 7-8% - so I assume that's equilibrium. Do I need to have the new wood all the way down to 7-8% before I start working on it, or if I get to, say, 9% is it okay to move ahead?


Thanks, in advance.

[Lee Schierer]

Your readings reflect what I would expect to see after a few days. Your thoughts that the center is still higher are right on.

If your pins are longer than you can push in drill some pilot holes leaving them shallow enough that you still have room to push the pins into the wood to get a reading deeper in the wood.

I would think it would take more than a month for the wood interior to get to 10%

[Gary Ragatz]

If your pins are longer than you can push in drill some pilot holes leaving them shallow enough that you still have room to push the pins into the wood to get a reading deeper in the wood.

Thanks, Lee. Used an awl to make some pilot holes for the meter, and I seem to be at 12-13% - looks like I have to wait a little longer for my bench!

Gary

[John TenEyck]

For reference, 35% RH is just about 7% moisture content.

To find out what the average moisture content is, cut a fresh piece out of your scrap, a couple inches square or so, doesn't really matter as long as you can weight it accurately. OK, weigh it on a kitchen gram scale, then put it in an oven at 220F. Weigh it every hour or so, and when the weight is constant for 3 consecutive readings it's oven dry. The moisture content of that piece before you put it in the oven was:

(Wet wt - Oven dry wt) / Oven dry wt x 100 = % moisture

You can use the same general process to determine when your wood is at equilibrium with your shop. Just weigh a much larger piece, something at least 10 - 12" long. When the weight stays constant it's at EMC with your shop. And of course you can confirm that by cutting it and checking the inside with your moisture meter, or drying a small piece in the oven again. I think it will take your wood several more weeks before the weight remains constant. I wouldn't use it until it's no higher than 2% above EMC.

John

[Gary Ragatz]

For reference, 35% RH is just about 7% moisture content.

To find out what the average moisture content is, cut a fresh piece out of your scrap, a couple inches square or so, doesn't really matter as long as you can weight it accurately. OK, weigh it on a kitchen gram scale, then put it in an oven at 220F. Weigh it every hour or so, and when the weight is constant for 3 consecutive readings it's oven dry. The moisture content of that piece before you put it in the oven was:

(Wet wt - Oven dry wt) / Oven dry wt x 100 = % moisture

You can use the same general process to determine when your wood is at equilibrium with your shop. Just weigh a much larger piece, something at least 10 - 12" long. When the weight stays constant it's at EMC with your shop. And of course you can confirm that by cutting it and checking the inside with your moisture meter, or drying a small piece in the oven again. I think it will take your wood several more weeks before the weight remains constant. I wouldn't use it until it's no higher than 2% above EMC.

John

John,

Thanks for your reply. I probably won't get quite so scientific/empirical as to weigh and bake my wood, but it seems clear that I will have to wait a while before going to work on my bench. Per your suggestion, I'll be looking for MC < 9%.

Your post prompted a Google search, which led me to a calculator linking temperature, relative humidity and EMC. I thought others here might be interested: http://www.csgnetwork.com/emctablecalc.html

Best,
Gary

[Jacob Reverb]

I don't know about longleaf SYP, but with loblolly (another species sometimes sold as SYP), I've read that you can go from green to fully air-dried in something like 90 days, FWIW.

The stuff dries FAST, and yet never seems to warp or twist or check much at all, no matter how fast you dry it.

[Andrew More]

I don’t have much experience drying wood – I usually just buy kiln-dried hardwood from my local guy, sticker it for a week or two to let it acclimate to the shop and then go to work. Recently, I ordered some 2x4 and 2x6 SYP from Menards, for a new workbench. When I brought it home, the moisture content was higher than I was expecting (ranged from 15% to 20%, using my cheap meter), but apparently that is where it was supposed to be – it’s graded KD19.

My experience with wandering the local lumber yards is that Menard's lumber has a higher moisture content, because it's stored outside. Naturally this is going to vary depending on your location, time of the year, what the weather has been like, etc etc. OTOH, I think the 2x12s are generally higher quality at Menards.

One other thing is that if I was making a bench I'd buy the 2x10, or 2x12s instead of 2x4s. Generally you're going to get a better cut of wood, less knots, less cupping/twists/warps. If you're really careful picking through the pile you can get some "quartersawn" pine out of the pile. You just need to check the ends, and dig through the pile.

[Gary Ragatz]

I don't know about longleaf SYP, but with loblolly (another species sometimes sold as SYP), I've read that you can go from green to fully air-dried in something like 90 days, FWIW.

The stuff dries FAST, and yet never seems to warp or twist or check much at all, no matter how fast you dry it.

I'll keep checking it with the meter every two or three days. I'd kind of like to get started, but the bench has been on my "to do" list for quite a while, so a little more waiting won't hurt.

[Gary Ragatz]

My experience with wandering the local lumber yards is that Menard's lumber has a higher moisture content, because it's stored outside. Naturally this is going to vary depending on your location, time of the year, what the weather has been like, etc etc. OTOH, I think the 2x12s are generally higher quality at Menards.

One other thing is that if I was making a bench I'd buy the 2x10, or 2x12s instead of 2x4s. Generally you're going to get a better cut of wood, less knots, less cupping/twists/warps. If you're really careful picking through the pile you can get some "quartersawn" pine out of the pile. You just need to check the ends, and dig through the pile.

Andrew,

I saw that suggestion about going for wider stock somewhere else - about three days after I placed my order with Menards. :p

None of the big box stores around here stock SYP, except for some short stuff. Menards was the only one where I could even order it - so no chance to pick through the pile. Good news is that what they picked for me seemed to be in pretty good shape. One 2x6 with a bit of a bow, but I think I can work around that - and I ordered about 20% more than I need, so I can afford to reject some when it's time to build.

[Andrew Seemann]

As important as the moisture content, when you are using framing lumber for a bench, is to watch the grain pattern when you are orienting boards for assembly and gluing. You want to avoid gluing vertical grain to flat grain, and you want to avoid using wood that has the pith in it or cut near it (the wood where you can see the center of the tree or the grain is nearly a half circle). Gluing vertical grain to flat grain, especially on a wood with wide growth rings, will likely cause a crack at the joint due to the wood expanding and contracting at different rates. Wood with pith in it will want to cup and uncup with the change in the seasons, especially in a place like Michigan with wide swings of humidity between summer and winter. Framing lumber is often cut from as small a tree as possible for the board size. 2x4s seem to be the worst offenders for having pith in them, 2x6s less often, but it does happen.

No milling or drying ritual will change this, it is just a function of how wood reacts to moisture and the geometric effects that result from wood grain being naturally curved. That said, you still do want the boards to settle down to closer to equilibrium before milling them up.

[Richard Coers]

That 64 degree shop air sure isn't doing you any favors. Not sure a fan will get it to 9% on the inside. Might want to tent it and put some heat to it.

[Andrew More]

None of the big box stores around here stock SYP, except for some short stuff.

Sorry to hear that, guess I'm a bit spoiled, living in Ohio, it's about the only thing they sell around here. You must be in the uppie.

[Gary Ragatz]

Thanks, Andrew.

The stock I have is, for the most part, flat grain. I guess I'll try to alternate the grain pattern when I glue up the top - probably not much more I can do beyond that. The good news is the bench will live in the basement, and we run a de-humidifier in the summer, and run a house-wide humidifier during the winter, so even though it's Michigan, the variation in humidity level will be modest.

Gary

[Gary Ragatz]

That 64 degree shop air sure isn't doing you any favors. Not sure a fan will get it to 9% on the inside. Might want to tent it and put some heat to it.

Richard,

Some other stock that I have had in the basement for a while (a few months) is down to 7-8%, so I guess the new stuff will get there eventually. Fortunately, I have the flexibility to wait on it - not a time-sensitive project.

Gary

[Gary Ragatz]

Sorry to hear that, guess I'm a bit spoiled, living in Ohio, it's about the only thing they sell around here. You must be in the uppie.

It's funny. I'm in East Lansing ~ 90 minutes from the Ohio border. I did a little poking around, and stores near Detroit don't stock SYP, stores in Toledo don't stock it, but down near Columbus and other parts of Ohio, then they have it. Maybe what's available around here is wood that is grown in Michigan?

Looked at the tracking info, and the stuff I ordered came from a Menards distribution center in Holiday City (never heard of that), Ohio.

[Andrew More]

I'm down in the Cincinnati area, which isn't THAT far away I wouldn't have thought, but who knows what actually goes on in the big box store logistics. I'll have to ask my brother about it sometime, he's up in Detroit.

[Andrew Seemann]

Thanks, Andrew.

The stock I have is, for the most part, flat grain. I guess I'll try to alternate the grain pattern when I glue up the top - probably not much more I can do beyond that. The good news is the bench will live in the basement, and we run a de-humidifier in the summer, and run a house-wide humidifier during the winter, so even though it's Michigan, the variation in humidity level will be modest.

Gary

Actually, if it all flat grain, that is ideal. Glue the top together with the grain vertical and you basically end up with a big laminated quarter sawn top. When I did my Frid bench, I took flat sawn maple, cut it into 2 1/4 inch wide boards, turned them 90 and glued them up, and ended up with a nice stable quarter sawn maple top.