Dryng wood in shop

[Nick Lazz]

Hey everyone...if this is the wrong forum please let me know.

I am drying wood in my heated shop (heat pump). It is a stick framed building that is well insulated. I also have a fan circulating air around wood.

My question: do you think I need a de-humidifier too? If so, I have no idea what kind to get. I have seen some at home depot online i.e. 30qt - 70qt, but unsure if those types would have any effect.

It does appear to feel a little humid in the shop. Heat is set at 64F...which isn't hot but definitely warm. I'm just wondering if I am wasting my time and electricity. I would like to use this wood as soon as possible...but realize it will take some time. I was just hoping my efforts wood speed the process up, and not too aggressive.
Thanks for your help, as always.

Nick

[Richard Coers]

What species of wood? Dead wet, or has it been air dried outside? How much wood, and how thick?

[John TenEyck]

Without a moisture meter and humidity gage you are flying blind. You can buy a very serviceable moisture meter for around $100. A Humidity gage is maybe $10 - $20. So, for the price of a few BF of lumber you will be able to determine what the moisture content is of your wood, and what the equilibrium moisture content is for wood in your shop. Where are you in the PNW? The rainy or the sunny side of the Cascades. If you are on the sunny side, you probably won't need a dehumidifier; if you are on the rainy side it would be a pretty safe bet you will. Your location will also determine, to some degree, how much you need to dry your wood. For much of the country 8% is a reasonable MC to shoot for, exceptions being the desert SW and the rainy PNW. So it's important (for us) to know where you are. If you don't know then MC of your wood is the least of your problems ! Just kidding. Give us a little more info. and I'm sure we can help. Also, if you don't have a copy of Bruce Hoadley's book "Understanding Wood" that should be on your list of things to buy, too.

John

[Rod Sheridan]

Hi Nick, as others have said you need to be able to measure the humidity and the wood moisture in order to dry the wood at the correct rate.

If it dries too rapidly it will be ruined.

Another issue is that the moisture released from the wood will rust all your tools and machinery, hopefully you're not really drying wood in the shop, but in a separate building.

get some books, start reading................Rod.

[Nick Lazz]

I'll try to answer several of your guy's questions in one post....
I have a moister meter and can check the wood...right now it is over 30%+...It is fairly wet...but my meter maxes out. The 2 species I have drying are Redwood (was going to use it possibly for a bar top in a bonus room...I know, prob not the best choice but I will save that for another discussion.) and a Black Walnut/English Walnut combo from a grafted tree.

I have several planks of both. They range from 9'-7' in length and are 2" or 8/4 thick. I believe I have roughly 150 bdft of each species. They are currently stickered on my concrete floor in my wood shop. I wondered about possibly surface rust on table saw etc...but I have left the heat on and a fan so I have good airflow. Also my shop is heated and air conditioned with a heat pump, so I believe my heat source is somewhat dry - removing humidity, albeit slowly. My thermostat is currently set at 64F so I am trying to keep the shop warm but not hot.

I am in the wet side of the PNW...not too far from Portland, OR.

Thanks for all your help. Looking forward to your posts.

Nick

[Charlie MacGregor]

Nick, I'd start with a $30 hygrometer, then if needed, a Borg dehumidifier. As it's a somewhat hostile enviroment, the extended warranty might make sense. Also try to keep the coils/fins as free from dust as possible. As others have stated above, check the drying rates for your two species. As you've indicated, you can excercise some control with air flow(fans), temperature, and relative humidity. It's not an ideal situation, but if you're careful you should be able to end up with relatively few defects and safe iron tools and surfaces.

[Doug Herzberg]

If your shop is separate from your home, have you considered running your heat pump in AC mode for a short time each day? It's basically a giant dehumidifier. If your thermostat has a timer program and can auto select heat/cool mode, you could program some brief periods of extreme temperature swings (maybe 10 degrees?) to force the compressor into dehumidifier duty. You would be paying to reheat the air you just cooled during the cycle, but that may be cheaper than purchasing a separate dehumidifier for this duty.

[Carl Beckett]

If your shop is separate from your home, have you considered running your heat pump in AC mode for a short time each day? It's basically a giant dehumidifier. If your thermostat has a timer program and can auto select heat/cool mode, you could program some brief periods of extreme temperature swings (maybe 10 degrees?) to force the compressor into dehumidifier duty. You would be paying to reheat the air you just cooled during the cycle, but that may be cheaper than purchasing a separate dehumidifier for this duty.

Definitely consider this before buying a stand alone dehumidifier. Many heat pumps have a dehumidifier mode even.

[John TenEyck]

Your wood is at or above the fiber saturation point - it's still really wet; you have gallons and gallons of water to remove. If I were in that situation, I'd build a plastic tent around the wood and put a fan and small dehumidifier inside. I've been using a dehumidifier to dry wood in my home built kiln for almost 10 years with no ill effects; however, the new ones do have much smaller coil openings and will probably clog up quicker with sawdust, so you may need to blow it out with compressed air more often. Maybe you could find an older, working one on Craigslist, etc. Anyway, the heat from the dehumidifier running will probably provide enough heat inside the plastic tent that you probably won't need to heat your shop. If not, you can add a couple of lightbulbs inside to raise the temp. enough to drive out the water.

You stated you wanted to use the wood ASAP. To do so, you need to dry the wood in a controlled way. There was an article in FWW in Nov./Dec. 1991 that shows how to do that. You have to follow a drying curve based on how many square feet (not BF) of lumber you have and the initial moisture content. It involves weighing the water every day and adjusting the setting on the dehumidifier to stay on the drying curve. I built an automatic control system to do this, but it can be done manually as well. If you have 300 BF of lumber at 30% MC, I'm guessing it will take at least a month to safely dry it down to 8 - 10% moisture so you can use it.

If you send me a PM I can provide some more info from the FWW article if you can't locate it.

John

[Jeff Duncan]

This is well outside my area of knowledge so take it for what it's worth, however it is my understanding that this initial drying is most often done outside as good airflow is necessary through the pack of lumber. Also as mentioned there is a LOT of water that needs to be removed and not ideal to have that inside a building. Just keep in mind when your trying to re-invent a process you may have a tough time finding valuable information. Meaning your basically experimenting with your wood and process.

As far as drying time it's a rule of thumb that it takes about 1 year per inch of thickness. This is just an average though so you'll need to depend on your moisture meter. If you want it faster your looking at either sending it to a kiln or building your own kiln.

Anyway that's about all I've got....good luck!
JeffD

[Mel Fulks]

Some woods actually have to be air dried before being kiln dried. I have heard that poplar is one of them and that very warped and twisted rough poplar is the result of kiln drying wet lumber. The drying schedules can probably be found on line. Forest Products Laboritory?

[John TenEyck]

Some woods actually have to be air dried before being kiln dried. I have heard that poplar is one of them and that very warped and twisted rough poplar is the result of kiln drying wet lumber. The drying schedules can probably be found on line. Forest Products Laboritory?

Urban legend.

John

[Carl Beckett]

One additional thought:

Consider your end state humidity when drying. That is - it seems to me at least (and I am by no means an expert in wood drying) - that you want the MC of the wood before building, to be as close to the end state of where the finished piece will be.

So if you have a climate controlled shop that is close to the same climate control as your house (assuming the finished piece will land there), then equilibrium should be at this end state goal.

If you are shipping it somewhere else. Or if you leave your doors and windows of your house open a lot - this could affect the end state. Or a particularly dry or moist climate would affect your end goal.

Relying on an absolute moisture content might not be the best objective?? (or perhaps, getting it 'low enough' means in a relative sense, limited/acceptable amount of movement when it changes from this MC%)

Maybe take a small piece of wood inside and leave it there (for weeks/months). Check the MC of where that piece equilibriates, then try to match it with the wood you are building with.

[Keith Christopher]

If there is a local sawmill with a kiln, my suggestion would be take it to them. almost all will let you 'rent' space/time.

[Nick Lazz]

Thanks for all the feedback guys. I will see what my heat pump is capable of.
For the record, this stuff did air dry in a dry drafty barn for several months (prob 6 or less). I will look into that article from FWW. I would like to be able to use this stuff in the next 6 months by speeding up the process slightly in my shop...that was my goal, because I had heard the same 1" per year rule of thumb for air drying.

If nothing else I will post my results here if anyone is interested. Might be helpful to someone down the road.

Thanks again. This forum and its members are all very helpful.

Nick