Rapid drying experiment - spindle stock

[Kevin Stanbary]

I have some recently cut black locust. Tree was taken down in late July, I got 5 decent sized logs that day, sealed the ends of logs with some old polyurethane just because it's what I had at the time (I've since acquired a big bucket of Anchorseal.) 2 weeks ago I found some time and cut it all into slabs and a few bowl blanks and properly sealed the lot.

Long story somewhat shorter, I decided I had a need for some spindle blanks from the stuff and was pondering a way to get it dry. I've been using DNA for bowl blanks with a fair amount of success and I was reading about boiling methods and I had an idea...

I cut three 3 1/4" x 3 1/4" x 14" blanks and dropped them in DNA to soak. I think they ended up being in for 4 days.

I pulled them out on my way into work one morning, taking them along. Once I got to the office I stacked them with stickers in the environmental chamber we have for temperature testing electronics. Set the chamber to 115 degrees C (239 degrees F) and left them there for about 4 1/2 hours.

When I opened the chamber I was greeted by some *very* humid hot air and a lot of condensation. The blanks themselves, once they had cooled enough to touch had some cracking and checking at the ends down to about 1/2" in.

Took them home, cut off the cracked stock and sealed the ends. They sat for a week or so before I got back to them but after cutting through the blanks, they appear to be completely dry all the way through and there's been no more cracks developing since. Unfortunately I don't have a moisture meter, so I'm not sure how dry they really are. Put one of the blanks between centers and turned it round and was getting chips and dust instead of curls.

I think I'll be experimenting more with this, but at this point I'm wondering if I got lucky with the minimal cracking I got or if I'm on to something here... Unfortunately, I'm guessing not may people have access to a chamber like this and I don't think I'd try it in a normal oven - not enough control of the temperature.

Anyway I thought I'd share and see what you all thought of it... As I play more, I'll be sure to share my experiences.

[Reed Gray]

Not really sure about it. I know that radio frequency (micro wave) drying has been tried commercially, but it didn't catch on. I don't think you had the same thing going though, sounds like it was just heat. It would be interesting to try it some more to see what kind of results come out. I know solar kilns heat up to 150 to 180 degrees F and then cool off over night. This allows some drying, but then at night the wood gets to 'relax' and relieve the stress. Maybe heating it and keeping the humidity in there was a good trick, as in steaming, or boiling if the wood reaches constant temperature throughout the piece.

robo hippy

[Aaron Wingert]

I don't think a week is enough time for a 3"+ DNA soaked blank to dry before turning. When I DNA dry my 4" wide by 1-1/4" thick blanks for turkey calls, it takes over a month for them to be ready. Sometimes two. The best way to determine when the drying process has ended is to periodically weigh the blank on a scale that is sensitive enough to register small changes. I use a gram scale I stole from my wife's kitchen, and write the blanks weight on the blank itself every few days. When the blank stops losing weight it is assumed dry. I never seal the end grain of DNA soaked wood. After soaking, my blanks go into a paper bag or several layers of newspaper. After a couple weeks I open the bag or unwrap the paper and let them continue to dry. I've never had too much trouble with checking using this method.

The DNA accelerates the drying process significantly. I wouldn't expect great success at trying to accelerate what is already an accelerated process.

[Kim Ford]

There are two kind of moisture in green wood. That which is in the capillary system and that which is within the cells. In order to get wood dry you need to get both out.

Getting the capillary moisture out is pretty easy, it primarly comes out through the end grain, this is the moisture that the went from the roots to the leaves or vise versa and is still present in the wood. The moisture in the cells is a little more difficult however. The cell wall actually has to rupture for this to occur.

When you air dry wood the cell wall ruptures as it drys out over time and the moisture is released and migrates out of the wood.

When you put wood in a kiln the heat expands the water in the cell causing the cell wall to rupture and the moisture can then work it's way out. Same thing happens when you boil the wood or put it in a microwave.

If you put it in a vacuum kiln, the vacuum causes the water to bubble rupturing the cell wall and the vacuum extracts it from the wood.

When you soak wood in DNA the alchool causes the cell wall to rupture thus releasing the moisture but it still needs to find it's way out.

Kevin, It sounds like you did a little of both, but moving that much moisture through 3" of wood takes a little more time unless you extract it with a vacuum. I would think that you dryed out the outsite inch or so but still have moisture deeper down.

Good experiment, let us know how it turns out.

[Leo Van Der Loo]

Here's some info on how wood dries, and another very good place for information on drying wood is from the US forest lab, here's a link to how the drying is done and why.

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr118.pdf

how wood dries and why it can split doing so.jpg