Speed drying Alder wood and burls?

[Cushing H.]

I noticed another fellow that sells slabs close to me has made a booth out of a wood frame and plastic....a bit like a greenhouse but only about 5 feet tall. He had a fan at one end and small opening at either end in the plastic. I assumed it was an effective way of drying faster, but I never talked to him about it. The guy sells hundreds of slabs a year so I'm sure he knows what he is doing.

Randy - what you just described is a solar kiln ... the purpose is to speed up the drying without cracking. It is basically ... wrapping the wood in plastic and putting it in the sun. You guys get pissed at me when i talk science and mechanisms ... so i will just leave it at that for now.

i would not recommend trying anything different on some really nice piece of wood ... but if i were to have a piece i would not cry over, i would likely try it. If it fails ... well, my neighbor has a nice fire pit in the back yard...

 

[weo]

Went well until the day I forgot to put a couple candles back and my wife started questioning the kids. They gave me up in seconds!!!

I would have liked to be a fly on the wall for that exchange.....

Will it be adviceable to cut burls into thinner pieces in order to let them dry faster, like 5 cm thick slices?

I don't have much experience with Alder, but I went a bit thicker with my maple. A few years ago I was impatient (and had enough) that I tried a little experimentation where I cut a few slabs into blocks ~ 2 1/2" x 6 1/2" x 3 3/4". My thinking was that when dry and cutting/sanding off any warping, checking, and taking the blade kerf into consideration this would yield me 3 handle blocks 2" x 6" x 1 1/4" . I didn't keep the best notes, but this worked to speed up the process and while a couple of the pieces did split and/or twist enough where I couldn't get a full sized handle, most of them did well and went according to plan. So in short, this can work but might not.

Twisting or warping even seems to happen if you try to stabilize scales instead of blocks.

(although I would have changed this to read, "... especially if you try to stabilize scales...")

 

[weo]

You guys get pissed at me when i talk science and mechanisms ... so i will just leave it at that for now.

Awww... come on, now. I don't think anybody, especially Randydb, was getting pissed here. I think Ben was merely highlighting an important point to prevent those with less experience from ruining what may be their only special piece of wood.

OK, taking off my black and white striped shirt, and putting away my whistle now.

 

[Greenberg Woods]

Randy - what you just described is a solar kiln ... the purpose is to speed up the drying without cracking. It is basically ... wrapping the wood in plastic and putting it in the sun. You guys get pissed at me when i talk science and mechanisms ... so i will just leave it at that for now.

i would not recommend trying anything different on some really nice piece of wood ... but if i were to have a piece i would not cry over, i would likely try it. If it fails ... well, my neighbor has a nice fire pit in the back yard...

My experience is generally in more difficult to dry woods, things like cocobolo, desert ironwood, ebony and the like. It may well be effective for more forgiving woods, but in my experience even a single afternoon of sunlight causes rather severe spiderweb cracking on woods. I guess it would depend on the thickness and opacity of the plastic, weather it was being used purely as a green house, i.e the light passed through the plastic to be absorbed by the wood and thus heat it, or if the plastic was opaque enough to be heated itself by the sun.

In my person opinion, burl and curly lumber is inherently more difficult to dry, and when combined with its higher value, I would reccomend against any attempts to artificially speed up drying at an increased risk of cracking.

 

[Cushing H.]

My experience is generally in more difficult to dry woods, things like cocobolo, desert ironwood, ebony and the like. It may well be effective for more forgiving woods, but in my experience even a single afternoon of sunlight causes rather severe spiderweb cracking on woods. I guess it would depend on the thickness and opacity of the plastic.

Ben ... re the effect on harder to dry woods ... i am not sure i have a guess ... but here are my thoughts. My understanding is that cracking occurs because of gradients in moisture within the wood. Heat the outside, the surface looses moisture to the outside air ... that surface wood shrinks ... the wood inside next to it does not, and ... CRACK.

i would think exposure to sun would heat the exposed surface, drive water out if that surface, and cause your spiderwebs. BUT ... note i said “water gets lost to the surrounding air”. IF you wrap in plastic, the humidity inside the wrap goes through the roof, and moisture loss, even from a heated surface goes way down (because water will always move from an area of high concentration to one of low concentration).; remove that concentration gradient, and the water goes nowhere.

when you heat (like inside a kiln) you increase the ability of water to move through the wood ... but if you simltaneously close up the container around the wood, you drastically reduce the moisture gradient inside the wood (thus reducing cracking). It seems contradictory, but it is the way the physics work out. (There are a lot of industrial drying processes and materials that use this understanding ... house paint being one of them ... it is engineered to NOT dry so fast that it produces a “skin”.

So ... back to the original question ... i would think wrapping in plastic is a no-brainer. Putting it inthe sun would be a go-carefull thing (rotate it?, maybe put inpartial shade? No sun at all until the moisture is down to a certain level?). In either case, agreed it should not be tried with a precious piece of wood...

 

[Greenberg Woods]

Ben ... re the effect on harder to dry woods ... i am not sure i have a guess ... but here are my thoughts. My understanding is that cracking occurs because of gradients in moisture within the wood. Heat the outside, the surface looses moisture to the outside air ... that surface wood shrinks ... the wood inside next to it does not, and ... CRACK.

i would think exposure to sun would heat the exposed surface, drive water out if that surface, and cause your spiderwebs. BUT ... note i said “water gets lost to the surrounding air”. IF you wrap in plastic, the humidity inside the wrap goes through the roof, and moisture loss, even from a heated surface goes way down (because water will always move from an area of high concentration to one of low concentration).; remove that concentration gradient, and the water goes nowhere.

when you heat (like inside a kiln) you increase the ability of water to move through the wood ... but if you simltaneously close up the container around the wood, you drastically reduce the moisture gradient inside the wood (thus reducing cracking). It seems contradictory, but it is the way the physics work out. (There are a lot of industrial drying processes and materials that use this understanding ... house paint being one of them ... it is engineered to NOT dry so fast that it produces a “skin”.

So ... back to the original question ... i would think wrapping in plastic is a no-brainer. Putting it inthe sun would be a go-carefull thing (rotate it?, maybe put inpartial shade? No sun at all until the moisture is down to a certain level?). In either case, agreed it should not be tried with a precious piece of wood...

I have my black and white ebony wrapped in plastic, in a cardboard box, hidden in the back of my workshop.

I will give the same commentary I gave about wood stabilizing. Theory is a useful thing and should guide your ideas, but in the same way that maple, a very fine pored wood absorbs vastly more resin than camphor, a relatively open pored wood despite what the theory would dictate, I strongly advice against trying to accelerate the drying of fine woods.

The fact that most cocobolo, ebony, ironwood, african blackwood and lignium Vitae are sold wet, despite the fact that they are regularly ~60% more expensive when dry speaks to my point.

Can you stick wood in a kiln? Yes. Can you make a solar kiln? Yes.

As someone with 8 years of experience working with, processing, buying, selling and drying woods, would I reccomend you do it?

No.

If its something you would like to experiment with, I would be very interested to see data, but I will continue to dry wood as slowly and as carefully as possible.

 

[Cushing H.]

Ben ... you are reacting to something I never said. I never said I advocated throwing “fine woods” into a solar kiln. In fact I said I would not try it with wood that is difficult to replace or that I would cry over if it shredded itself. There is a phrase I have often used: “we are in violent agreement”. I think we have reached that point here.

 

[Randydb]

I get where Ben is coming from. I have some burls that are going to produce15-25 blocks some day when I cut them up. That is a lot to screw up if I am messing around with speeding up drying.

I get that Cushing is looking at this with a "scientific" logical lens too. For me I find that intriguing too. I was wondering how a wood drying kiln worked. The mill where I bought some fir posts has a shipping container they use for a kiln. They put giant stacks of lumber into it and drop the moisture content from 36+% down to about 14% wayyyy faster than air drying. It makes sense that trapping the moisture coming out of the lumber around the wood helps it dry evenly and avoid cracking. I MAY be beginning to understand the science behind this, BUT I am definitely not going to be trying it any time soon. I don't want to make a mistake and ruin my nice wood.

 

[Cushing H.]

Thanks randy ... and i do appreciate your comments ... i do though think that there is a mismatch between what i am *trying* to say, and how i am being heard. Yes, i am trying to understand the drying process mechanism to throw out there a possible slightly different approach ... but that is all i am thinking of it as. The “science”, as you put it, in my mind does nothing more than hint at pieces of what that different approach might be (like ... wrapping the wood in plastic). I am not trying to make any firm predictions ... but ... why the heck not occasionally try something new???

and i have several times said i would not advocate this with pieces of wood that you would cry about if it was damaged. So lets try a slightly different approach. Randy - you seem to have access to lots of different “found” wood. What if you came across a piece, maybe spalted, that was interesting, but not spectacular. Maybe you could take it home, wrap it in plastic, and put it on your deck in partial shade... and check it periodically. If it tears itself to shreds.. then never do it again. If it does not ... then maybe try again, but put in more sun (until you get a feel for how much sun it can take). Maybe you get to the point where you do this with a better piece of spalted wood ... or maybe even a found burl. I say “maybe”. I am making absolutely no prediction whether this will work or not ... i am only saying, based on what happens in a kiln, that it might be interesting to try it. (If i get permission to pull found wood out of my local parks, i will likely try this myself ... just to see if full sun tears the wood apart)

i said you guys get pissed at me when i talk about “mechanisms”.

 

[noseoil]

If you're in a hurry for good wood, buy some dry or stabilized wood & have at it. Good wood needs to air dry slowly & can take a few years to dry, depending on the thickness, type & moisture content.

There's a gunsmith in Tucson I know who won't touch a fine stock without letting it air dry for a few years. He then does what's called a "progressive reduction" when doing the profile. He waits a while between each step of working the blank into a finished stock, to allow for internal stress relief as the shape changes. For anyone in a big hurry, I would suggest a good kiln-dried micarta.

https://huntforever.org/2015/07/02/the-rifles-of-david-miller-co/

 

[Randydb]

If you're in a hurry for good wood, buy some dry or stabilized wood & have at it. Good wood needs to air dry slowly & can take a few years to dry, depending on the thickness, type & moisture content.

There's a gunsmith in Tucson I know who won't touch a fine stock without letting it air dry for a few years. He then does what's called a "progressive reduction" when doing the profile. He waits a while between each step of working the blank into a finished stock, to allow for internal stress relief as the shape changes. For anyone in a big hurry, I would suggest a good kiln-dried micarta.

https://huntforever.org/2015/07/02/the-rifles-of-david-miller-co/

I find this intriguing too. The internal stresses and how even small amounts of moisture content changing causes issues. I have numerous 1.5"x1.5"x24" flute blanks that have been in my garage for over 4 years and are quire dry. But every once in a while I cut one length wise and run a groove down the centre with my router in preparation to make a flute and a day or two later the pieces have warped or twisted significantly. Sometimes up to a half inch bend in each piece. There is a lot going on I just don't understand.

Cushing, I know that burls act way different that just a normal piece of the same species of wood. I'd be happy to stick a couple pieces of maple in plastic and see how the moisture content goes. I'm pretty sure I would need to open it up every once in a while to let moisture out of the plastic too. But I'm not testing on my precious burl!

This is one of the slab dining tables I did. I bought that slab. I have a number of burls around 18 inches across that are drying. Not worth as much as this one, but they will make some nice handle blocks.

 

[Cushing H.]

I find this intriguing too. But every once in a while I cut one length wise and run a groove down the centre with my router in preparation to make a flute and a day or two later the pieces have warped or twisted significantly.

Cushing, I know that burls act way different that just a normal piece of the same species of wood. I'd be happy to stick a couple pieces of maple in plastic and see how the moisture content goes.

This is one of the slab dining tables I did. I bought that slab. I have a number of burls around 18 inches across that are drying.

I dont doubt that internal stresses develop as a result of drying ... and that this can produce warps when the outside “supporting” wood is cut away. How that stress might be relieved beats me - maybe the fibers are able to “slide past” each other a little? Ben would likely know about that.

Randy - Out of curiosity, how do you observe burls to behave differently? I know they do not have the fairly consistent grain structure of regular wood - do you see more cracking?

i was not actually asking you to wrap some wood in plastic ... just trying to use your example of access to various types of wood to describe how this might be tried. Agreed with the need to periodically unwrap ... or maybe over time punch small vent holes in the plastic?

fwiw - last summer i bought a slab of cherry burl from a guy here who gets various wood from farms in southern MN. The slabbed burl was *kiln dried* right with the rest of the slabbed straight grain cherry. The burl came through just fine (and not the first time he has kiln dried burl - btw, he makes slab tables also). Just one data point .. but it is actually that experience that made me wonder if creating a “mini solar kiln” out of plastic *might* give the OP the result of faster drying of burls.

nice table!

 

[weo]

I dont doubt that internal stresses develop as a result of drying ... and that this can produce warps when the outside “supporting” wood is cut away.

If only I had taken some time lapse pictures yesterday of the last ~12" piece of maple from the tree I cut down 3 years ago that was the crotch where the single trunk split into 4. I started by cutting the split/checked areas off to get to the solid part in the middle, taking about 2" off all around and squaring up the block. I got down to a solid piece and went to grab lunch. When I got back to the block about 30 minutes later, the once solid block, that had 4 bulls eyes and a rectangle of curly figuring had split and checked in 4 places, giving me a good demonstration the internal stresses that I had freed up by cutting away some material.

 

[Cushing H.]

If only I had taken some time lapse pictures yesterday of the last ~12" piece of maple from the tree I cut down 3 years ago

That would have been cool

 

[Randydb]

Randy - Out of curiosity, how do you observe burls to behave differently? I know they do not have the fairly consistent grain structure of regular wood - do you see more cracking?

Remember I'm not an expert by any stretch. But for me I notice on a regular piece of wood I get checking running with grain, twisting and/or warping or some combination of these when things go wrong or just when drying. Because I am using found wood that on the pacific northwest I am mostly drying birch, alder, maple, walnut and a bit of apple and cherry. My experience with apple and cherry has been the worst for splitting into pieces. And maple seems to want to move a ton, but maybe not check as much. The first maple slab table I did(8' long) would cup almost 3/4" corner to corner in the winter, and then have a 1/2" raised crown down the centre in the summer. That is an amazing amount of movement. Eventually I made a steel square tubed frame that I bolted to the bottom of the slab and that stopped the majority of the motion.

I don't notice my burl table moving at all (although it has a steel frame) But the smaller burls I have dried just seem less predictable. If something goes wrong with them it seems to be checking in any direction they feel they want to. They are just more valuable to me so I am way more careful to prep them with paint/wax and not take chances.

For me it boils down to having seen enough wood unexpectedly check/warp/twist that I realize I don't know enough to know when/if I am pushing the boundaries. There are sooo many variables I don't recognize. So I have my air dry pile and it is big and long enough that I usually have some wood that is ready when I need it.

 

[Cushing H.]

I don't notice my burl table moving at all (although it has a steel frame) But the smaller burls I have dried just seem less predictable. If something goes wrong with them it seems to be checking in any direction they feel they want to. They are just more valuable to me so I am way more careful to prep them with paint/wax and not take chances.

I would believe that with the burl table - since it lacks the consistent alignment of wood fiber to "add up" the deformations along its length. (I have sections of wood floors in my house that open up nice cracks between boards in the arid winter, and those cracks completely close up during the humid summer)

A thought - with straight grained wood people paint the ends, which is the cut ends of the fibers. But burl does not have that consistent structure ... and you likely get just as much moisture loss out of the flat as you do the ends (which the cracking that results from that). I am going to try to say this carefully ... so no flames please .... but would you not get better protection of the piece if you painted the entire thing (maybe that is what you are doing??) ... but then it might never dry out, or .... ahem (again, please no flames) .... wrap the thing somewhat loosely in plastic and put in a nice dark cool place ... and do your thing about periodically removing the plastic? (no "solar kiln" here .... just something like a reversible full-body paint job )

 

[Greenberg Woods]

I would believe that with the burl table - since it lacks the consistent alignment of wood fiber to "add up" the deformations along its length. (I have sections of wood floors in my house that open up nice cracks between boards in the arid winter, and those cracks completely close up during the humid summer)

A thought - with straight grained wood people paint the ends, which is the cut ends of the fibers. But burl does not have that consistent structure ... and you likely get just as much moisture loss out of the flat as you do the ends (which the cracking that results from that). I am going to try to say this carefully ... so no flames please .... but would you not get better protection of the piece if you painted the entire thing (maybe that is what you are doing??) ... but then it might never dry out, or .... ahem (again, please no flames) .... wrap the thing somewhat loosely in plastic and put in a nice dark cool place ... and do your thing about periodically removing the plastic? (no "solar kiln" here .... just something like a reversible full-body paint job )

That's exactly how most fine burls are dried. While a full over wax seal is effective, its often overly cautious and cleNi g the wax off is a huge pain.

For a lot of difficult to dry woods, I wrap them tightly in plastic and store them in a dark space in the workshop

 

[Cushing H.]

For a lot of difficult to dry woods, I wrap them tightly in plastic and store them in a dark space in the workshop

And put a rabbits-foot on top of them for good measure? I have several pieces of ebony on my wood rack that I am massively scared to use after hearing stories (including from you and Stacy). They would be really nice as bolsters or end pieces on Wa handles, but .......

Have you ever tried punching a few small vent holes in the plastic? Or have you found even that to be overly aggressive?

 

[Randydb]

And put a rabbits-foot on top of them for good measure? I have several pieces of ebony on my wood rack that I am massively scared to use after hearing stories (including from you and Stacy). They would be really nice as bolsters or end pieces on Wa handles, but .......

Have you ever tried punching a few small vent holes in the plastic? Or have you found even that to be overly aggressive?

I just paint/wax the exposed part of the burl where I cut it off and toss it on the pile most of the time. The odd piece goes into a couple of shopping bags and onto the pile if it is really precious.

Poking holes in the bag would be too much like "pushing til I found the edge" and I know that I will be minus a nice piece of wood when I find the edge!!

 

[LCoop]

Interesting discussion. I have a question though. How does the wood dry at all completely wrapped in plastic?
I mostly have used finely curled maple. I stack it my attic of my garage and depending on the thickness of it as to when I cut scales from it. Knock on wood I've not had a problem. I've dried other woods ( curly maple, sassafras, walnut and red elm) like that back when I made fiberglass laminated recurve bows and those at taken down to 100 thousand at the thick end and tapered down .002 per inch for 36"