Quick Questions on "acclimation" of newly received wood.........

[Odie]

We've all heard about allowing new (to your location) wood to acclimate to your location before turning.

I've never paid much attention to this, because most all my wood purchases are wood above 12 percent MC, and the majority is well in excess of 12 percent. This level of MC requires controlled seasoning. For seasoning bowls, I rough the bowl without stopping, and immediately completely anchorseal. Sometimes I do this on the same day I receive it from the shipper, or very soon after receiving it. I really don't think any "acclimation" is necessary for wood with high MC, unless your intentions are to finish turn immediately........but, what is your thinking on this?

It would make sense to allow kiln dried wood, or anything that meters under 12 percent MC to acclimate before turning to a finished state......so, if you slap a newly received very dry 6 pecent MC KD, or other, less than 12 percent piece of wood on your lathe that will likely rise, or drop in MC immediately, you are asking for an uncontrolled warp.

Seasoning in the high twenties to high thirties of percent MC is more difficult to handle....... This seems to be the most difficult wood to make behave without losing it. Warping can be dealt with by making wall thickness generous. The rule of thumb is 1/10th inch for each inch of diameter. That works pretty well, but it's hard to tell what the warp factor will be, without having a crystal ball! On suspect roughed bowls, I make them extra thick. The basic rule is not absolute, and a turner should allow for a few failures.......around 2-3 percent failure rate seems to be the reasonable expectation for unexpected warping, cracking, and fungus related problems.

My other question involves the upper limits of MC, and dealing with fungus, mold, mildew, etc. What are you other turners doing about this problem? Is it better to rough immediately, or allow the wood to self-season (in block form) to a certain percent MC, prior to roughing? I have generally always roughed high MC bowl blanks without much hesitation, so I'm unsure if there are benefits to leaving wood in block form for a period of time. Do you think these fungal problems are only related to surface exposure to the atmosphere, or will they occur in the interior of a wood block? (Spalting would be the exception, but only speaking of those fungal problems that tend to ruin a good piece of wood) Are these growths the result of the climate in the final destination, in transit, or where the wood originally came from. (I'm sure species is a factor in the equation, as well.)

I suppose someone who has many blocks of wood from a fresh downed tree, and the same tree, could experiment on the pros and cons of the fungus questions, and expect some answers that would give some realistic data for comparison.......but, I seldom have blocks from the same tree.......

OK, what do you think?

ooc

 

[Bill Boehme]

Odie, I presume that you are talking about air drying wood. However, the term "seasoning" is frequently used on some woodworking forums where the folklore goes something like, "when you buy a batch of KD hardwood for a furniture project, you should acclimate it to the environment where the end product will be used for a week or two before you start working it". I's pretty obvious what I think about the second scenario where nothing meaningful is going to happen to the KD lumber in a week or two. Same thing goes for air dried lumber. It's a different story if you bought wet lumber and you made a big mistake unless you plan to sticker it and air dry it yourself.

Turning blanks and lumber are different animals and buying wet blanks is not a problem if properly handled. Anyway, I agree that if you receive wood that is still fairly wet, then Anchorseal it or rough turn and then Anchorseal immediately, but don't let it lay around and start cracking. The reason for Anchorsealing is to slow down the rate of drying so that there is not a steep change in moisture from exterior to middle of the block of wood. I am surprised that the seller hasn't already sealed the end grain.

If you buy KD hardwood turning blanks at 12% MC or less, then it is about as dry as it is going to ever get. The free moisture is gone and so is most of the bound moisture. If you get any warping from turning such a piece of wood, it is something other than simply moisture. It could be that the wood was not properly kiln dried or it could be reaction wood. But is is not simply from the moisture content of the wood changing. Once the bound water is reduced to that level, it is not going to subsequently change significantly.

Tropical wood is what I find most troublesome when it comes to cracking and shrinking. For that reason I stick mostly with local types of wood.

I don't have much experience with fungus. Around here it is usually too hot and dry to worry much about fungus unless intentionally trying to get spalting. My limited experience is that exposure to moisture and ground contact are the environmental conditions to create spalting or other fungus rather than air exposure. One exception is pecan -- if left on the ground for any significant length of time, it will spalt. And then it will rot. One club member covers the wood that he wants to spalt with a pile of horse manure for about six months.

I prefer to leave my wood in long log sections rather than cutting it into small blocks. This minimizes cracking and drying out.

 

[MichaelMouse]

Bill may think it's "folklore", but the wood believes in acclimatization. If you don't believe a few days can make a difference in moisture content, remember how much weight that last greenwood turning lost in the first week. Stickering flat stock for a week or so can eliminate some of the surprises that might occur, even when dealing only with bound water. Simple, documented fact.

It's distance from air and difference in humidity that count. You get a blank that shows 15% on your meter, and that's good for as far as the probes go, no farther. What's inside is a mystery. If it's REALLY wet inside and your shop's REALLY dry, you can open or accelerate existing checks without half trying. Matters not if the wood has been in a kiln once. If it hasn't been for a few months, it's the same as the chunk next to it that was aged in the air.

So we play it safe. Hurts nothing to Turn/Dry/Turn, so we do it, changing the entire dynamic of the block. It's now 1" lumber. That's in thickness. In length it might get to three-four inches. If it's got good shape and/or low enough moisture to keep dampness from coming out the endgrain centrifugally or pneumatically, set aside, and check the warp. Weigh when the warp's close to your estimate.

If the shape's problematic, the wood flinging wet and the shop very dry, might want to bag or coat, your choice. Fungus starts/grows OK at 20%, not much at 15, so it's a race between water loss and fungal gain.

No believer in the 10% rule, I. One of those mnemonics with little meaning. The wood contracts on itself. It's distance in contiguous wood that determines the total dimensional shrink, as well as direction of grain. The 1" endgrain on the rim can be stressed pretty hard by the 5" broad bottom unless care is taken to make the shape take up some of the difference. What I do believe in and anyone can easily document, is that wood a half inch thick dries three times as fast as wood one inch thick in radial and tangential orientation. I worry more about too thick than too thin. Anywhere from 5/8 to 1" is good enough for me on a 16" lathe. Thinner for those pieces where I already have a good vision of the end product, thicker for possible revision.

 

[billooms]

If I get wood with 12% moisture, then I wrap it in plastic or seal the ends and allow it to dry for another 6 months. Why? Because else it will crack within a day (yes, it's happened to me).

Where I live (Arizona), the "acclimated" wood in my shop is 4% MC or less. So it depends on where you live. You need to know what the equilibrium moisture content is. Measure some stuff that has been in your shop for a year and you'll know.

 

[dbonertz]

Acclimating your wood is a good practice to get into. Even when putting hard wood flooring in your home they want to stack the wood in your home for at least three days to acclimate. This wood has most likely been in a warehouse in the same local climate you live in but your home conditions will differ than the warehouse condition that it came from. Turning blanks are not much different with the exception that they often times come from an entirely different climate than what you live in (if purchased from a source).

A question for MM. I think most understand that when drying wood that free water is fairly easy to shed and the first to go. But to dry the bound water the cell cavity needs to be for the lack of better word cracked or opened or compromised for the water to leave. I have read the information on the forestry site (same site you often post) but nowhere is it written, at least that I can find, that when wood takes moisture back on is it bound or free water moisture. I can only assume since the cavity has been broken that any water that is taken on by the wood after drying is now free water rather than bound water. Is this correct? If my thinking is correct then wouldn't wood that has been kiln dried acclimate faster than air dried which may need to shed more bound water to acclimate into its new environment?

In regards to the 10% guideline it is just that a guideline. Once you become familiar with the woods that you are using and have experienced drying it then start playing with thinning it under the 10% guideline or in some cases maybe more than 10%. Quick story where I dried some elm. I had dried quite a bit of elm so I felt confident that I could on 9 and 10 inch bowls rough to a 5/8" to 3/4" wall thickness. Some in this batch warped so bad that the inside rim dimension in one direction was the same as the outside rim dimension going the other direction which made it useless to get a bowl out of it. There are lots a variables when drying wood such as species, branch wood versus trunk wood, orientation from pith and etc. Unfortunately when wood is purchased from a source rather than cut yourself you cannot always know form where on the tree it was cut. So, to me, this is where the 10% guideline becomes very useful to many people and has proven over many years to work.

 

[MichaelMouse]

The "cavity," you are referring to? You mean the cell walls? They're almost always open. How else would you share side to side in the wood? Look at Ch. 3 in the Wood Handbook, specifically Figs. 3-6 and 3-7. Shows the secondary system for lateral transport. The ray system is primary. Takes a while for the unbound moisture to move out through those systems, since there's no capillary draw as along the grain. Thus the roughly 12:1 ratio of loss from end compared to face grain. Quarter even slower.

Whether water is bound depends on the availability of bonding sites on the sugars that form cell walls. Not all sites are occupied, even when there's unbound water available. The amount of energy available to break the bond depends on temperature and humidity differential. The air carries the water away when it breaks free of the H bond, until the bond/debond ratio stabilizes. The ratios for grain orientation and re-uptake are probably close to the same as for drying.

You can add water that will get pulled into the vascular structure, and some will bond, but if primary conditions of RH, which depends on temperature and absolute humidity haven't changed, it'll start flying away immediately.

As to your 10% and elm. The reversals and swirls in elm are legendary, such that it is not predictable. Same with curly birch. Lare-area irregularities. Impinging branch wood and reaction wood is much more more predictable, and can cover smaller areas, so use your eye from choosing the spot in the log to watching fuzz in strange places when hollowing. Leave a little more thickness where things are weird, but it's structure over species.

Fairly straight stuff is going to be governed by the tangential 10 to radial 5% difference. Why 5% is a reasonable bet.

 

[dbonertz]

Thanks more to study. Always interesting in that handbook but sometimes hard to make the connections without asking questions.

 

[Bill Boehme]

Bill may think it's "folklore", but the wood believes in acclimatization. If you don't believe a few days can make a difference in moisture content, remember how much weight that last greenwood turning lost in the first week. Stickering flat stock for a week or so can eliminate some of the surprises that might occur, even when dealing only with bound water. Simple, documented fact. ...

Applres and oranges, MM. You are talking about green wood and I clearly said kiln dried wood (KD = kiln dried).

 

[MichaelMouse]

Swing and a miss, I guess. Wood is wood. The evaporation example was as dramatic as I could come up with, but it has apparently not hit its target. Matters not the source of the water, might even be that wet down to fuzz up. If there's water there and humidity is spare, it'll leave. Since you can't see the bound water, the example dealt with unbound, and lots of it.

How about this? Wood Handbook, chapter four is free, and will give you raw and interpreted data to enlighten. Everyone who works wood ought to have it, or Hoadley somewhere close. If you're a visual learner, try http://www.pbs.org/woodwrightsshop/video/2900/2906.html Moving pictures.

No magic in a kiln, or we'd never have to worry about drawers/doors getting tight in humid summers or panels rattling in their frames and showing white edges in a heated house, right? Not that we must if the maker knows the truths of wood and water from any of the places above.

 

[MichaelMouse]

Thanks more to study. Always interesting in that handbook but sometimes hard to make the connections without asking questions.

Some looks at relatively straight stuff. Less my photo skills, they show cured to ~10% cherry.
http://i35.photobucket.com/albums/d160/GoodOnesGone/Picture-Package-10.jpg Mortise lost 1/8 of an inch. No matter if it were in the bottom of this 10" piece or a 14.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Picture-Package-14.jpg Apparent loss in total diameter is close to the same - 1/2 inch fairly evenly divided. Not all of this is shrink, of course, at least half is drop along the grain as the piece tries to straighten its annual rings.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Edge-Droop.jpg Not one of the other cherries, but I didn't plan a "series". Tall walls pull more at center than sloping. This piece of oak is a classic.
http://i35.photobucket.com/albums/d160/GoodOnesGone/1-Oak-Distorted.jpg
Heart still warps as advertised, but with a little bit of something extra with this inverted sweet birch. http://i35.photobucket.com/albums/d160/GoodOnesGone/Heart-Down-Platter.jpg

Put this on the wall and use it to help determine which to favor - quicker cure or caution.
http://i35.photobucket.com/albums/d160/GoodOnesGone/LogEnd.jpg

 

[Odie]

Swing and a miss, I guess. Wood is wood. The evaporation example was as dramatic as I could come up with, but it has apparently not hit its target. Matters not the source of the water, might even be that wet down to fuzz up. If there's water there and humidity is spare, it'll leave. Since you can't see the bound water, the example dealt with unbound, and lots of it.

How about this? Wood Handbook, chapter four is free, and will give you raw and interpreted data to enlighten. Everyone who works wood ought to have it, or Hoadley somewhere close. If you're a visual learner, try http://www.pbs.org/woodwrightsshop/video/2900/2906.html Moving pictures.

No magic in a kiln, or we'd never have to worry about drawers/doors getting tight in humid summers or panels rattling in their frames and showing white edges in a heated house, right? Not that we must if the maker knows the truths of wood and water from any of the places above.

I think MM is making an important point with the "drawers and doors" example.

Wood in the low range of MC does acclimate....and it's important to allow for it.

Acclimation is not important for very high MC

The 1/10th inch per inch diameter is a good and sound rule for roughing bowls prior to seasoning. Like all rules, it won't necessarily cover every single example, but it is a rule of thumb, because it works.

In the original post, I was unsure of why I did things like I do, but I was aware that the common thinking works. Now I'm getting a little better understanding why the common beliefs work.

Thanks to all who posted......am looking forward to any further input.

Would welcome discussion on preventing mildew, fungus, etc., in solid blocks vs after the roughing stage.......if anyone has thoughts on that.

(BTW: Bill......none of my suppliers send me bowl blocks that are not sealed on the end grain......many of them are sealed on six sides.)

ooc

 

[MichaelMouse]

Easy answer, though given many times. <18% MC won't continue. General and easy information http://en.wikipedia.org/wiki/Spalting

Sara wrote her dissertation on the subject. http://www.finewoodworking.com/Materials/MaterialsArticle.aspx?id=32485

http://www.finewoodworking.com/blog/woodworking-life/tag/spalting

She likes woodturning, too.

 

[Bill Boehme]

.... Would welcome discussion on preventing mildew, fungus, etc., in solid blocks vs after the roughing stage.......if anyone has thoughts on that.

(BTW: Bill......none of my suppliers send me bowl blocks that are not sealed on the end grain......many of them are sealed on six sides.)

ooc

I don't have any solutions, only sympathy. A number of years ago, the local Rockler's store was getting large pallets of tropical wood from Peru -- all sopping wet and sealed in shrink-wrap plastic and growing mildew and all other sorts of decay stuff like crazy. The pieces were labeled with all sorts of fanciful names that I am sure were concocted to stimulate sales or get around export/import laws. If you remember Jim King from Peru who was active on several woodworking forums, I am pretty sure that his company was the supplier mainly because he was really proud of the shrink-wrap machine that his company got to seal the moisture in the turning blanks so that they would not dry out and crack.

I bought a few pieces after the prices were reduced to practically giving them away. I am glad that they were cheap because I never had much success in keeping them from cracking once unwrapped. The wood that did not crack or that I managed to glue back together was beautiful, but probably not worth the effort that I went through to salvage them. I still have one unturned piece that is about eight years old now. It might not start checking if I turned it, but I sort of doubt it.

By the way, I found out that Anchorseal couldn't keep the wood from checking so there was some purpose in using shrink wrap although it had the undesirable side effect of promoting the growth of fungi.

 

[Odie]

My findings also are close the the 18 percent mark as to the point where fungus, mildew, etc., is no longer going to grow or continue.

I wonder if roughing a high MC bowl, and then putting it into a heated environment so that the reduction in MC takes place more quickly (to some specified point of MC, and then season normally) could influence, or prevent the growth of mildew and fungus.....?

I don't know, but I'm envisioning an enclosed box with a light bulb, of small space heater for this. Maybe run the MC down to some point where the fungus won't initiate, and cracking won't occur.........maybe from a very wet 36 percent +/-, to around 20 or 25 percent???????

Just an idea.......never thought of it until just now. Anyone tried it?

ooc

 

[dbonertz]

You're basically talking about a kiln with your box and heat source. You can do what your suggesting but depending on where you live and the RH your equilibrium may be 16% to 18% so why not dry it in your kiln to that level.

 

[MichaelMouse]

My findings also are close the the 18 percent mark as to the point where fungus, mildew, etc., is no longer going to grow or continue.

I wonder if roughing a high MC bowl, and then putting it into a heated environment so that the reduction in MC takes place more quickly (to some specified point of MC, and then season normally) could influence, or prevent the growth of mildew and fungus.....?

Think about it. Mold/mildew must start at the surface, and that's also the place which, absent all other fussing, will dry fastest and first. If you don't create a microenvironment to keep the fibers expanded, you'll be all right. Might get some surface checks that develop into full splits if it dries too fast, of course. If you make a drying box, shoot for <80% RH humidity. That's 16% EMC at STP. Not too fast to crack any but the most careless shape, and fast enough to stay ahead of mildew. The big boys with kilns dry to ~20% outdoors to save money, then put the pallets in the box. Might be they know something about risk.

I've got a basement here, so I put them in open air for two/three days to shed max water, then where the air is still and the RH ~65%. Been so long since I lost any that I can't remember.

Do not put them in the draft of a heating duct. DAMHIKT.

 

[Dale Miner]

I wonder if roughing a high MC bowl, and then putting it into a heated environment so that the reduction in MC takes place more quickly (to some specified point of MC, and then season normally) could influence, or prevent the growth of mildew and fungus.....?

ooc

Odie,

No experience (good at least) on preventing mildew staining in/on blanks. For preventing the grey staining on roughouts, a washdown with boric acid post turning before laying up to dry has worked very well for me. I wrote a 'Tips and Tricks' blurb for American Woodworker about the use of boric acid.

Disolve the boric acid in water, and brush the solution on the roughout. When the water dries, the fungicide (boric acid) reamains on the wood and leaves a non friendly surface for fungus to take up homesteading.

Boric acid is not free of health issues, so check out precautions before deciding on it's use. The health issues are minimal, but worthy of precaution.