Getting Some Emperical Data on Drying

I don't have any data on my method of drying bowl blanks. However, I've been using the same method for well over 30 years and have successfully turned and dried thousands of pieces during that time. I live in hot, dry Arizona, so I'm drying wood under severe conditions.

I rough-turn and VERY liberally coat it with Johnson's paste wax. Two coats if I think it's necessary. I put the date of turning on it. The wettest of woods will be dry in 6 months. If it's a wood that is prone to cracking I'll also paper-bag it for a month or so. At the present time I have 50 to 60 pieces in various stages of drying. None are cracked. I do admit that I have experienced cracking, but not often.

My shop isn't air conditioned, so I don't rough-turn in the hot summer months.

You didn't mention Dave Smith's method of alchol drying. Dave tested for 3 years before he published his method. His method cuts drying time from months to weeks. I've read many reports from other turners who tried his method and like it.

There's plenty of anecdotal information/opinions/theories about the various methods of drying wood. While interesting and thought provoking, there's very little quantitative data to go with the opinions/preferences/favorites - what wood, its initial condition, how it was cut, how it was turned, what the ambient conditions were, what type of wood it was.

What I'm shooting for is to come up with a procedure that will provide some hard data. So the questions are what to sample what the samples should be - solid cylinder, hollow cylinder, square block etc. what to measure - initial dimensions, initial MC, ambient relative humidity, ambient temperature, . . . when to measure - once a day, week, month, year when to stop measuring how to evaluate results of a given method - change in dimensions, checks, cracks, splits, . . .

If a method could be developed and agreed on, folks could fill in the blanks for various woods and starting point grain - quarter sawn, radial sections, axial segments etc. Results could be compiled by some foolish volunteer and shared with this group and others.

Let's take the LDD method. The samples might be 2" diameter by 6" long cylinders, green, MC in the 25-30% range, weighed then all but one soaked in a 50% LDD, 50% water for some period of time, say 30 days. The extra non-soaked sample would be the control sample - left to air dry. The samples could then be removed, rinsed, toweled off , weighed and measured. It could then be evaluated in terms of number of splits, cracks, checks etc. Then, cross sections at 1/2", 1", 1 1/2" up to 3 " could be visually inspected for evidence of penetration depth of the LDD, compared against the control sample. Several samples could be left uncut and turned instead, with others left to air dry to equilibrium moisture content and re-evalauted.

This is just an example off the top of my head. There may be different parameters to keep track of depending on if you're doing between centers spindle type stuff vs hollow forms. bowls, platters.

So anyone have any quantitatively measurable parameters that should be in the method?

charlie b

Wow, this is a big project! I can understand the intent, however, I am not sure the data are going to be scientific. There are many variables that are almost impossible to track, such as the "details" of the wood used: where on the tree was it from, what was the grain structure like, quartersawn or backsawn. how well did the tree grow (stressed or well cared for, etc), and so on. How many control samples do you want to include? I'd suggest you need more than one.

Good luck. There are many good books on statistical analysis you can be thumbing through whilst you await the arrival of data!

Safe turning, Alan

Charlie: Good luck with this endeavor, but like the old saying: "Its been done before." Lynn Mangiamelli set up a questionnaire such as you describe and asked all the woodturners to make copies and fill them in on each of the pieces they were to turn. He got 11 replies which were of no real value as not big enough sample to draw conclusions from. I suspect that he and I learned that woodturners want to turn wood, not fill out two page questionnaires on the provenance and breeding and turning of their wood.

A fellow who came on the group said he was a biologist as well as a biochemist and that he would try to work out how LDD worked with wood.. Unfortunately, he soon ran into a problem as the machines necessary to evaluate the pieces were expensive to run and he really couln't devote company time to the project due to his busy schedule. So that concept was given up and we once more lapsed into an agnostic state, relying once more on anecdotal evidence.

NB: LDD is not for drying wood!! It is meant to serve as an intermediary agent between cutting down green wood and the cutting, turning and sanding of the item. For some unknown (but speculated upon) reason, LDD keeps the wood from drying out too rapidly hence, cracking and warping.

Leif

Actually, ALL of it is applicable, but I think the hobbyist is the limiting factor, not the science or technology. It's just that either the hobbyist isn't willing to learn the technical terminology and methodology being used, or aren't willing to buy or build a miniature industrial wood dryer.

You'd be better off finding a few turners with science skills to develop and run a small project on a task force basis. To ask a group of people, some of whom may not know what a control is, to develop an experiment will end up being frustrating at best.

Word of caution: The fewer the cooks the better.

Dan

When I did the alcohol experiments, I used 1" cubes, the easier to measure distortion with, cut from the same 1X1. Seemed as fair a method as I could devise. Since I was concerned with start/finish, I didn't bother with moisture readings, which, as long as they're at or above the FSP, don't mean anything.

Fortunately, we have the folks at FPL who have done thousands of experiments and measurements for us who have provided us with tables of EMC values at various relative humidities. They even have advice on which woods are more prone to end checking. Most of this "discussion" would not be taking place if more people would read the available data, which correlates remarkably with reality as it exists in my neighborhood. Instead, people talk about proof in things like freezing willow and surviving it, when willow is a favored wood for cricket bats and wooden limbs precisely because it doesn't split easily. The answers are there, but mystery and magic are more powerful.

As to faster drying or less distortion with alcohol soaks - the soak is to the soaker. If it did work, it would certainly not be for the "reasons" given, which violate the laws of physical science.

Would seem the pros are the hardwood furniture or floor guys. My thinking would be that their experience should be relevant. My problem is that my limited exposure to their processes indicates a very large scale/cost situation which is why we end up trying to find other methods around here. Sorta like Po Folks have Po Ways.

So, I guess what we're searching for is what they're doing but in little guy terms and conditions. The goal is a piece of wood that won't change its shape appreciably after final work. And goes from tree to lathe a lot faster than 1" per year. Or maybe more accurately from rough lathe to final work.

I'm surprised at Lief's "not cracking..." versus "drying..." comment because I mistakenly thought the purpose of LDD was to get to the final phase faster.

George refers to the government's forestry info - I wonder if he knows of other actual wood industry comments. Some of those engineers while understanding their process could maybe extrapolate it to our scale. In fact, how come we don't have any of those engineers turning wood and commenting here on the RCW? And, then again, maybe that extrapolation is evidenced in the vacuum chamber dryers, or microwave procedures already discussed.

Maybe some are as dumb as me. When I've read government data on trees so far, or even detailed books, I tend to fog over and fall asleep. I guess I want to know when the train arrives and where's it's going, not how steam engines are built. The details of the story are often relevant but I don't usually have the time to spend on that aspect which is probably why Lief's experience was 11 folks. Certain people are so inclined and we thank God for them when they succeed in publishing a Reader's Digest version of the topic.

TomNie

I posted this elsewhere, but will repost it here since it is on point. Someone already has done testing on small scale vacuum drying. It is from the Forest Product Journal (not associated with Forest Product Labs).

It looks interesting and doable. I have the equipment I need to give this a shot. I do large oval turnings, so need lumber in the dimensional range between

4"T x 8"W x 18"L to 6"T x 18"W x 48"L. As soon as I get a piece of wet wood milled from a log I'll give this a shot.

Dan

One turner's voodoo is another turner's logical method that works for him. I should say works for each of us because most all of us have our favorite way to dry wood and are fairly well satisfied with it. Of course we all wish for the perfect method, but we are mostly resigned and believe that our failures are the fault of the timber or failure to follow protocol. Some failure proof drying methods (not Leif's 'G') are in reality nothing more than hopeful suggestions that seemed to work for somebody who could persuade others. Our individual drying problem seems to be largely in convincing others that our method works and their's doesn't. We discuss drying methods endlessly, but we usually just keep on drying wood our way. We turners are true believers and I wonder how many of us would change our methods and abide by the results of any scientific study. It's not good science if there is no provision for failure, but the half life of of the findings of even the best funded and well designed studies isn't very long. Witness the six o'clock news reports of leading edge 'break-throughs'.

I think there are too many variables in even a well designed timber drying study for this group to control or even to consider. I can't remember details, but there was a famous scientist whose failure to include the dimensions of his lab. ruined an otherwise elegant experiment. Newton wasn't entirely right, although his laws seem totally valid.

I do understand that the problem is real and in no way do I belittle any reasonable approach to it. I hope this comes across as an unsophisticated caution from a guy who can't even get the AAW sharpening CD to play, not as pejorative or a knee kick negative. Should yet another effort be made to resolve or better understand the drying problem I hope it is completed, regardless if the outcome is positive, negative or inconclusive.

Turn to Safety, Arch Fortiter

=====>Whoops. Think I was unclear in my reply regarding LDD. I said, " For some unknown (but speculated upon) reason, LDD keeps the wood from drying out too rapidly hence, cracking and warping."

I should have phrased the above sentence to include the word "not" right after "hence," to insure understanding that the LDD prevented cracking and warping.

Leif A prophet is not without honour, but in his own country, and among his own kin, and in his own house. *SIGH!*

I wonder if that's true. The LDD should reduce the surface tension of water and thus allow it to flow more readily.

Arch, looks like it's a DVD, not CD. Use the DVD player and I opened with Windows Media Player.

caution from a guy who can't even get the AAW sharpening

It's not the surfactant. It's the Madge factor, where glycerol, a miscible liquid with considerably less vapor pressure than water is added. It'll stick around in and near the surface for a while.

Thus the glycerol blocks the pores even though the surfactant reduces the surface tension of the water?

No, the glycerol stays, water goes. Raoult's law. But water is not transported as quickly from the interior, because the surfactant has lessened the cohesion of the molecules. Adhesion to the fiber structure is normally overcome by the cohesion of the water.

Interesting experiment possible , but since turned thin doesn't crack anyway, all you'd find is an answer to a non-problem. As a temporary measure, at least as good as putting the piece in a bag, which is neater and not as likely to spill.

I worked on a web version with Lyn for a short while but there was little interest from turners to track the results. Here's the web form and there's a link to a form for use in a personal file on that page:

I came up with Easy Street but it couldn't produce the document you mentioned. Help with instructions or email it direct to me. Thanks for the input. TomNie

Tom you need the wrap around "ml", it came up easy for me.

Have fun and take care Leo Van Der Loo

I could be wrong, and often am, but my guess is that if there were an engineer or two turning (and I'm sure there are) as a hobby, they are either simply not inclined to bother posting here, or they are afraid of making unqualified assertions on a rather arcane subject for fear of liability (perhaps in the case of using chemical compounds for drying) or damage to their reputations in a public forum. There are so many different types of wood and techniques that no matter what, any solution is going to be a godsend to some and so much snake oil to others. For my part, I'm a carpenter, so I feel free to speculate away- if I show ignorance about wood drying techniques, it's not going to scare people about my ability to frame a stairway or build a nice deck. If I were a forestry guru in the engineering dept. of a large sawmill, I might have a different outlook.

If that is the case, it tends to leave this sort of discussion to the amateurs, but that can be good as well. Leaves a little mystery in a craft that might be a bit less fun if every variable was controlled. I've spent time running production metal lathes, and it's awfully dull. No cracking, no warping, and no persistant fuzzy bits- but no fun, either.