Moisture on freshly cut lumber

[Grunex]

Recently I've ventured into using an Alaskan style slabber attachment on my saw as a means to use some of the timber from my land clearing business.  I'm new to milling and have so far managed to avoid some of the pitfalls that a lot of newcomers experience, but my question is this, I'm cutting logs that have been dropped in the woods and sun dried for about six months, and I know they are still "green" so as I stack the lumber for drying what are some layman's ways of telling if the slabs/lumber is dry enough for working for furniture purposes? I do not have a moisture tester and really don't have a ton of money to invest in tools and etc. so any help would be appreciated.  The slabs are a full 2" thick and the species is white oak, Ash, cherry, black walnut, and one log of butternut. thanks in advance.

[Kbeitz]

Moisture testers can be had cheap on E-bay...

[POSTON WIDEHEAD]

I got my 2 prong moisture meter at Slowe's for less than 30 bucks. You can get more accurant ones for bigger bucks but the one I use gets me by.

[Tom the Sawyer]

Grunex,

A meter would be a good investment but probably not accurate for a year or so (not reliably accurate above 30% MC). 

A very simple method, if you have an accurate way to weigh the slabs, is to track the weight of the slab.  It will drop quickly at first, then slow down and eventually level off.  That is when it is as dry as it can get in the atmosphere where it is stored.  Likely to take a couple of years.

[jaygtree]

at the mill where i use to work we figured a year per inch of thickness for air drying.  jg

[York Woodwright]

Here's a trick I learned from an older chap who worked before the days of moisture meters. Put the board up to your cheek. If it feels cool, it's too wet to use for fine furniture. If it doesn't feel cool, then it passes.

If there is significant residual moisture in the wood to bleed warmth from your cheek to the board, then the moisture content is too high. If there is very little moisture remaining in the wood, then the board will not cool your cheek and the minimal residual moisture will not affect your project.

Because my workshop is an absolute mess, there are occasions when I cannot find my moisture meter and I've used this method. Its works.

Oh, one caveat. It doesn't work with beards. Is there a lady in your life with a sensitive cheek? 

Charles

[Kbeitz]

Wonder how that would work in Alaska.... ?

[Ianab]

at the mill where i use to work we figured a year per inch of thickness for air drying.  jg

That would be a worst case scenario. Slow drying species, cold damp climate etc.

Of course if you follow that rule, your wood will be dry, so no harm done, but it might have been ready to use in 1/2 that time, or even less.

That's where a moisture meter comes in, even a cheap one will give you a good indication. If it says 20%+, put it back on the stack. If it's down under 15%, you can start calling it "air dry" and think about whether it needs more drying inside. Whether it's actually 14% or 16% isn't a big deal.

[Grunex]

Grunex,

A meter would be a good investment but probably not accurate for a year or so (not reliably accurate above 30% MC). 

A very simple method, if you have an accurate way to weigh the slabs, is to track the weight of the slab.  It will drop quickly at first, then slow down and eventually level off.  That is when it is as dry as it can get in the atmosphere where it is stored.  Likely to take a couple of years.

So then what you are saying is divide the wet weight into the dry weight to determine percentage of moisture dropped?  seems doable,  I've only got a small amount of lumber and it wouldn't be hard to select one slab for comparison on each batch cut.   I've got an older farm house with wood heat and in the basement I've got a heat exchanger with a fan behind it blowing warm air right over the top of the lumber.  winter time brings very dry air to my house so I'm thinking probably very rapid dry down may be the case here  any thoughts?

[Grunex]

at the mill where i use to work we figured a year per inch of thickness for air drying.  jg

That would be a worst case scenario. Slow drying species, cold damp climate etc.

Of course if you follow that rule, your wood will be dry, so no harm done, but it might have been ready to use in 1/2 that time, or even less.

That's where a moisture meter comes in, even a cheap one will give you a good indication. If it says 20%+, put it back on the stack. If it's down under 15%, you can start calling it "air dry" and think about whether it needs more drying inside. Whether it's actually 14% or 16% isn't a big deal.

what is the optimal moisture for working furniture grade lumber to avoid cracks and splitting?  16% or less?

[Kbeitz]

I was told making furniture you want around 10%

[beenthere]

Wood will always strive to equilibrate to the relative humidity conditions where it is at. 
So the optimum is whatever that condition is... so you will need to guestimate to determine that optimum. 

[Grunex]

sorry guys for the rookie questions,  my schooling background is metal working and machining, and of course farming and clearing seem to me to go hand in hand.  This is another interest that has come across my plate and I'm eager to learn.   

[Tom the Sawyer]

Grunex,

The setup you described would certainly shorten the drying process but don't try it with the white oak, it would probably cause surface checks, you can dry oak too quickly.

Tracking the weight won't tell you the actual moisture content, just give you an idea when it is equalized with the environment.  If you want to calculate the actual moisture content there is a procedure for doing that, checkout Drying Hardwood Lumber or several other publications. 

Basically, you take a representative sample of the material in question, weigh it and then dry it in an oven (low temp or microwave) until it loses no more weight (oven-dry) which would be approximately 0% MC.  Then you can calculate how much of the original sample's weight was moisture.

You don't want your project wood at 0% so you calculate what one of your project boards should weigh when it reaches the desired MC - say 8%.  For what you are doing, the starting moisture content is not that relevant.  When the weight of a sample board levels off you'll be at EMC - if you are building indoor furniture then the final drying should be indoors so you reach that level.

[Den-Den]

Some good information in previous answers.
* Moisture meters don't have to be expensive
* Different woods dry at different rates
* Drying too fast will cause damage to the wood
* Air drying outside (in most areas) will never get the wood dry enough for furniture work but it can get the wood dry enough to stop molding, rotting and make the final drying easier.

[Ianab]

* Drying too fast will cause damage to the wood

This can be an issue with many hardwoods,especially things like oak.

It would be best to air dry outside in the cool weather until it basically stops loosing moisture. This will be down to 10-15% depending on where you live and the season. Then it's safe to bring into a heated inside area and let if dry those last few %. It hard to mess up the drying at that stage.

If you bring green wood inside it's likely to dry too fast on the ends and surface, before the moisture can migrate from the wood at the core. The drier areas then shrink, and crack open (surface and end checking) Once you get the whole piece down to "air dry" that's unlikely, the damage is usually at the early stages of drying.

The main issue is the way the wood shrinks. It shrinks different amounts in different directions, and around different areas of grain. This can lead to all sorts of movement in the wood as it dries. So you make a table top out of part dried wood, then as it dries out inside it might cup or pull glue joints apart as the  wood settles into it's final shape. So it's best to get it fully dry, which is ~8% in most US homes, THEN you machine the wood flat, straight and square, and it should stay that way.

But air drying outside, followed by acclimating in an "inside" environment should get decent results.

[Grunex]

Grunex,

The setup you described would certainly shorten the drying process but don't try it with the white oak, it would probably cause surface checks, you can dry oak too quickly.

Tracking the weight won't tell you the actual moisture content, just give you an idea when it is equalized with the environment.  If you want to calculate the actual moisture content there is a procedure for doing that, checkout Drying Hardwood Lumber or several other publications. 

Basically, you take a representative sample of the material in question, weigh it and then dry it in an oven (low temp or microwave) until it loses no more weight (oven-dry) which would be approximately 0% MC.  Then you can calculate how much of the original sample's weight was moisture.

You don't want your project wood at 0% so you calculate what one of your project boards should weigh when it reaches the desired MC - say 8%.  For what you are doing, the starting moisture content is not that relevant.  When the weight of a sample board levels off you'll be at EMC - if you are building indoor furniture then the final drying should be indoors so you reach that level.

Thanks for all the honest answers on the drying. I'll probably just keep milling and build my stocks for the time being.  I do have a need to build some furniture soon, but I'm not all that willing to do it twice either so more than likely I'll just stack a few boards for small projects such as single plank shelving in closets.  I made a place in our pole shed for drying the oak as it is more than likely going to take a long time for me to get to the dining table anyway.   
With all this discussion on drying, how is it then that commercial sawmills can kiln dry lumber as fast as they do and get the results they do?
I used to work for a farmer who on occasion put a nibco heater in front of his solar kiln and poured the heat to it, several hundred bd feet of walnut and oak dried in that fashion at once.   any thoughts here?  good? bad? ugly?  the man used to cut for people who built furniture as well.

[Ianab]

Commercial kilns can precisely control the drying conditions. The temperature, humidity and air flow. Then there is a "schedule" for each particular species and thickness. If they try and push the process beyond that, they can ruin a load.

The issue with DIY drying is the lack of control. Drying can be too fast if you get hot, dry windy conditions. Or too slow if it's calm and humid, which leads to staining and mould.

Solar kilns use a clever system where they heat and dry during the day, then cool off and let the wood equalise at night. This means control need no be as precise. Takes longer than a big commercial kiln because you are only really drying for 8 hours a day. But it works. Adding extra heat during the later part of the drying should do little harm.

Once the wood is "air dry" it's pretty safe and you can sit it in a warm dry spot with a fan blowing over it to complete the drying.

If you want some wood to get some projects started, do you have some pine or cedar? Saw that into 1" boards and you can probably have it close to ready in a couple of months. It's also more forgiving to dry, you can bring a few boards in and hurry them along inside with little risk.

[Grunex]

Commercial kilns can precisely control the drying conditions. The temperature, humidity and air flow. Then there is a "schedule" for each particular species and thickness. If they try and push the process beyond that, they can ruin a load.

The issue with DIY drying is the lack of control. Drying can be too fast if you get hot, dry windy conditions. Or too slow if it's calm and humid, which leads to staining and mould.

Solar kilns use a clever system where they heat and dry during the day, then cool off and let the wood equalise at night. This means control need no be as precise. Takes longer than a big commercial kiln because you are only really drying for 8 hours a day. But it works. Adding extra heat during the later part of the drying should do little harm.

Once the wood is "air dry" it's pretty safe and you can sit it in a warm dry spot with a fan blowing over it to complete the drying.

If you want some wood to get some projects started, do you have some pine or cedar? Saw that into 1" boards and you can probably have it close to ready in a couple of months. It's also more forgiving to dry, you can bring a few boards in and hurry them along inside with little risk.

Thinking I'll saw for a good while, my wife and I read this thread together so from what she has said , we'll be taking the slow road and do it right the first time.  I've got a boat load of projects that need tending to outside as well.  (cattle fences, gates and panels etc)  for most of those we'll more than likely just saw and use green.  It's interesting to know about how things are done commercially as well as DIY methods and with a little planning we can cut now for drying and furniture use later and while we're waiting we can work on the less fussy business of fixing for the sheds. 

In my area in SE MN, there is pine and some cedar, just not where I'm clearing right now or in my own wood lot.  we used to have a lot of Butternut, and some really big trees too, but they have all died off and I'm not really sure why.   Some have said Butternut has a fungus that spreads and kills the trees and others have said insects kill them faster than anything. I guess without actually having a forester come in and look at the trees (what few there are of them)  I won't know for sure.   I have one log now, but it is such a small one 10" and only 8" long that I'll be treating that with kid gloves when I mill it.  Normally I wouldn't have cut it at all except the top of the tree was already dying.  Replanting of that species in my area is sorely needed I think.

[thecfarm]

As you said,use your boards you would not want for furniture for your projects.