Is there an ideal relative humidity for working with wood?

[HakeZou]

[Note: I wasn't sure where exactly to post this. Moderators, please move it if I have put it in the wrong place.]

 

We just moved to a new house and have been acutely aware of how much drier the air is here—relative humidity percentage is consistently in the 30s, where it was usually between 45 and 55% at the old place. Now that my current project and tools are unpacked, I was able to get some work done this morning. After placing a soaked plank on the hull, I could watch it dry (within 10 minutes that plank was no longer visibly wet!). Unfortunately, when I was cutting a plank of 2x3 limewood, I discovered that the drier air has made the wood significantly more brittle than I'm used to.

 

So, this raises a question for me: is there an ideal relative humidity for working with wood? I'd also appreciate any tips on working with wood in a drier climate. Thanks in advance!

[Jaager]

I have no definitive answers, just some thoughts:

Your finished product will "live" in what ever is the relative humidity of your interior environment.

A humidifier can be added to your HVAC system.  This will involve incurring added expense, attention, and maintenance.  It also involves constant isolation of your interior environment.  But you pays your money and takes your chances with this sort of choice.

I suggest that it is better to assemble in the same conditions as those of the finished object.

I would be more concerned about the transported finished models and how they fare when they equilibrate with lower humidity.

My suggestion is to step back to a wider focus and work with species of wood that are less brittle and more appropriate to begin with.  This does involve having to become, at the bare minimum, a magnitude more involved in what your shop will need.  Appropriate species are not easily obtained.

[druxey]

Stability of temperature and humidity is, I think, the critical thing. Changes result in swelling or shrinkage from the original ambient conditions the wood was in Some species are more stable than others, but all wood will 'move' with changing conditions.

[HakeZou]

Thanks, Jaager and Druxey. I'm still a real novice in this hobby, so appreciate the insights. So far, so good with the finished models, but I'll be keeping an eye on them.

[allanyed]

I have had the good fortune of sending several models to Europe, three of which are aboard cruise ships which cruise  in the Caribbean and European side of the Atlantic at times so there are changes in ambient temperatures and humidity even though there is climate control on board these vessels.    I think a sealed case will help a lot and of course some kind of climate control.  They had been at sea for a long time, one for over ten years,  without any ill effects.  A friend had cruised on one of the ships in the past couple years  and sent me a note that he had seen the model.  He  commented that it looked to be in perfect condition.   With the ships all shut down for many months now, I am curious to see how they faired with no climate controls during this shutdown period.   Maybe it's time to book a cruise on one of the ships to see for myself once this pandemic is over.  Oh, the things we are forced to do for our hobby.   😁

Allan

[Carlos Reira]

For working the wood, sometimes green (full moisture content) is best. Green hickory can be carved like cheese, and Tilia sp. (Linden, Limewood, Basswood) would work beautifully green. But for longterm stability, preventing cracking and gaps opening up, the wood should be at least as dry if not a little drier than the expected location where it will be placed.  This is why most woodworking is done with seasoned wood. Wood is hygroscopic like a sponge, but once it loses its bound moisture and goes through enough of a seasoning period, it becomes much less so. As you noted, dry wood is usually more brittle. If you want to restore some of the softness to the wood without effecting its stability too much try soaking it in a glycol-alcohol mixture, such as RV antifreeze, the pink nontoxic kind. There is also the commercially available high molecular weight polyethylene glycol (PEG) for wood stabilization, but I've never tried it. Gluing will be affected though.

[Thiscout]

The moisture content of wood for joinery is 6-8%.
https://bestwoodcarvingtool.com/