Is my drying environment dry enough?

[Nigel Tracy]

I have been turning in a wing of my basement, which is not insulated and lately has had a humidity of 60-80%, which is higher than it was in the winter.

I had a hunch that this space was cool and moist enough to air dry rough-turned bowls without bagging or anchorsealing. After roughing my last few bowls—two maple and one hickory-- then soaking them in DNA, I brown bagged for a day or two then opened them up and let them dry in the open air.

Well this seemed to work, and weighing them every couple of days revealed that about two weeks later the maple bowls had stopped losing moisture.

The moisture content, as measured by my pin meter seemes to be 10- 12%. Is this low enough to be stable and go ahead and finish turn?

I worry that my drying environment is now too moist at 60-80%, and getting bowls to 12% only. (Or maybe after the ten days they simply started drying at a much much slower rate.)

Since I haven’t been through four seasons of roughing, drying, and finish turning, I thought I’d ask for opinions from all the experience around here, so what do you think?


Thanks :)

[Steve Schlumpf]

Nigel,

I live Northwest of you and also have my shop located in the basement. The gauge reads 60% humidity and that is about normal this time of year. I store my DNA soaked turnings in my shop and they are usually ready to turn in about a month but I try to rough out enough turnings that I am in no rush.

Easiest way to find out if your bowls are ready to turn - is to turn one. Chances are 12% is as low as you are going to be able to get - seeing as to where they are stored and the RH. You'll know once you start turning if the wood is still to green as it will move on you while you are turning it. If that happens - remove it from the lathe and paper bag it for a little while longer.

[Nigel Tracy]

Hi Steve and thanks for your reply--much appreciated!

I was asking the question because I just finished a bowl, and after drying downstairs, finishing, then bringing upstairs, it moved a little in the following week in the dryer air. In the winter, finished bowls were not moving after being brought upstairs.

In the winter I did not measure their moisture content at any stage (I started doing that after recent suspicions) so I'll keep researching and hopefully come to some conclusions.

Thanks again!

Nigel

[Steve Schlumpf]

Nigel - just curious as to what you are using for a finish? Wood is going to absorb moisture any time it gets the chance and if not sealed really well has the tendency to move. How thick was the bowl?

[Scott Hubl]

For basement shop dwellers, what about using a dehumidifier to get the humidity lower in your shops?
Might help.

My "shop" is in my garage that is fully insulated with natural gas heat and a large window AC unit to keep it nice and comfy all year round.

[Steve Schlumpf]

Scott - I use a dehumidifier and try to keep HF down to 50% during the summer months. Problem is that when the temp is below 70* or so - the dehumidifier runs but doesn't really work very well. Once things warm up - works great and I have to empty about 3 to 4 gallons every day.

[Nigel Tracy]

Thanks again guys.

Yeah three dehumidifiers come down to the space for July & August and do a pretty good job of dealing with moisture. We hook up the outputs from the units directly to a drain so we're not emptying multiple times a day!

The dehumidifiers come down because the lower level of the building is used for our summer camp (but as the director I won't get much time to turn anyway...).

I did some more sleuthing/experimenting/learning on the moisture content topic and found a handy dandy chart that came with my moisture meter. It said that at 70-80% RH, wood will get to an equilibrium of 12%. And of course it will get to lower 8-10% at lower (normal) humidities of 40-50% (or something like that--can't remember the exact numbers).

In response to your question about the bowl(s), they've been a variety--cherry, hickory, and maple; avg 12", some smaller, one larger; and still experimenting with finishes too--danish oil, BLO, and buffing. The latest bowl in question was cherry with danish oil.

I think you're right, Steve, about wood just moving (as we all know) and I think I'm right that my drying environment is suddenly not really dry enough. So I've brought a few roughouts that are drying up to dryer air and we'll see what happens.

Can't thank everyone enough for all that I've learned here, but thanks once again,

Nigel