I’ve always heard that you should let newly purchased wood sit in your shop for a few days to acclimate to the humidity in your shop before working the wood. But what about the humidity in the place where the finished piece will sit?
My shop and my house have drastically different humidities much of the time. The shop is cold and unheated and is high humidity when it rains. The house has the heat going and is very very low humidity. So, what happens when I build a piece in the shop and then take it into the house, and the humidity suddenly changes as much as 50 or 60%? Is there any way to deal with this issue, short of taking all my power tools into the living room to do the buidling?
Holler
Replies
holler,
Any solid wood furniture should have provision made for seasonal movement. Avoid gluing cross grain construction, leave room for expansion/contraction in attaching tops, or fitting drawers, etc.
The reasoning behind allowing wood to acclimate to shop conditions has to do with avoiding a situation where the wood is still moving while you are trying to build with it.
Regards,
Ray
The most important thing is to avoid wood movement between milling the lumber and cutting joinery, hence the advice to let the wood acclimate to the shop environment. Trying to make dovetails, M&Ts, or frame-and-panels with twisted or bowed stock is no fun.
Once the piece is assembled, good construction techniques will allow wood movement without self-destruction. I'm thinking floating panels, tabletops attached to allow movement, sliding breadboard ends, etc. A good finish will help reduce the extremes of seaonal changes. Quartersawn lumber will also behave beter than flastsawn.
Having said that, 50-60% RH is lot of variation. I think you'd do well to seal up the shop and consider adding some dehumidification. Even a portable electric heater could help dry up a small shop.
For people just like you I provide an EMC table on the web.
http://furniturecarver.com/emc.html
This table will tell you just how much wood will fluctuate in moisture content when exposed to different relative humidities. Relative humidity and absolute humidity are two very different values and this table will help you determine just how much the EMC (equilibrium moisture content) of your lumber will change when subjected to different conditions.
Lee
Why don't you just clear out the first floor of your house -- except maybe the kitchen -- and move your shop over there?
"I would never die for my beliefs because I might be wrong."
-- Bertrand Russell
Your humidity worries between shop and house are mostly that- worries. The ambient humidity between the two is going to be similar. A lower temp with 20% humidity means a lower humidity when indoor air is expanded twenty or so times by your forced air furnace heating the air (and expanding its volume) to possibly even 2% humidity. This humidity level is damaging to any manufactured wood product. A humidifier in your winter heating system helps a lot by reducing those creaking sounds coming from furniture and the static electricity generated. A humidistat in your shop may be your best bet if you are concerned. Most normal natural humidity levels are not as damaging as the heated space ones that we create in our living spaces. Aloha, Mike
Holler,
You should acclimate the wood to your shop environment so that the stock isn't changing in dimension as you are making the piece, this allows you to do much better joinery.
Once the piece is made, if it is properly designed, i.e. with floating panels, table tops that aren't restricted by their attachment to the base, moldings that can slip if they run cross grain, good grain orientation, etc., the piece should remain intact no matter what environment it ends up in and no matter how much the humidity changes.
John W.
By asking the question, I suspect that you already know the answer. It doesn't require a lot of logic to understand that you may be taking perfectly good KD lumber back to air-dry level by improperly handleing it.
If you are getting advice from someone who lives on the Canadian border, and another who lives on a small island on the equator, and they are giving advice based on what works for them, without ever asking what situation you are working under, or knowing what their situation is, well maybe it will work for you, but maybe not. If you keep your shop 25 degrees warmer than the outside air in winter, then you don't need to cover your wood. If you don't keep your shop heated, then it is not much different from being under a shed outside.
If you are getting KD lumber, and know that the MC is low, and that the RH in your shop is high. my advice to you, is to work it as you normally would, and at nights, stack and cover it with a tarp or plastic to avoid picking up that extra moisture while it is in your shop.
Some readers here will swear that the wood has to settle down to your shop, as if something magic will happen within the wood that will make it better if it sits in the shop for a while.
Commercial Kiln dryers have the wood stickered while drying, and then stack it dead when they are done, to keep it from gaining the moisture back. The good ones even wrap the bundles with plastic to keep it that way, so you should do the same.
Now, within the tree, there may be some built in, actually grown-in tension or compression from one side of a board to the other that has been restrained by being weighted down in the stack. These boards may move considerably when they are removed from their restraint in the stack, then even more while being cut. If one side is under tension and the other is normal or compressed. You can cut them and watch them open, or close on the blade. You can straighten them and over night they will have changed again, and maybe even after another straightening. This is not due to moisture gain or loss, nor wheather they sat in the shop a few days or not. However it would be easy to see how someone cutting a board or two just home from the store that went crazy when ripped, yet let other more stable boards set for a while, might think that letting them set for a while would make a miraculous change.
Has anyone used a dehumidifier with in their workshop to lessen the effects of humidity on machinery and lumber? If so with what degree of success?
My shop and my house have drastically different humidities much of the time..
Talk the 'Little Lady into moving the saw into the living room?
Sorry I was just thinking again! My wife would have said OK if YA! vacuumed up a bit!
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