Moisture & drying time

[Andrew Arndts]

Okay I pick up some cherry today, large chunks 12"X12"X4 1/2" is just one of them. the others, though smaller, are not to far off. All 3 are between 30% and 35% moisture. Not wanting to turn them right now, I am just wondering, how many Years will I have to wait for them to get a bit dryer. Less than 10% I assume will be ideal since I reside in Michigan.
Sure I could dry it out via the oven or do a DNA bath... But I am Patient.

Thanks in advance

 

[MichaelMouse]

Twelve square, eh? Hope you sealed the ends tight, or you'll have end checks running within days. Never a good idea to shorten the pieces without it.

What's the problem with Turn, Dry, Turn? Certainly the percentage play with fresh-felled stuff. Rethink your position and get the centers out, or risk heavy losses. You're above the fiber saturation point now, and your meter is pretty nigh worthless. You could be over 50% easily.

How long to dry depends on the predominant relative humidity and the actual amount of moisture in the piece. If want to minimize degrade, you could be talking a couple of years to get it to ~15%. Depending on where you are in Michigan - upside or troll - that's as good as you'll get outdoors.

Free information for you at http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p Chapters three and four are the ones which bear most on your question.

Microwaving a large chunk is asking for a fire. Thick places often light off because they're well insulated by surrounding wood. Alcohol does nothing, unless you're going to soak and change baths for a year, so don't waste your time and money.

 

[hockenbery]

Turn it now.

a hollow forms can be turned to finished thickness.
bowls to finished thickness or roughed thickness.

If you roughed out a bowl with 11" diameter with walls 1" thick then dry it slowly. it may be ready to return in 6 months.

the rule of thumb for air drying lumber is an year for every inch of thickness
in air drying you loose inches off each end due to end checking
so in four years you may have a much smaller useable piece.

I often dry cherry in 3x3 or 4x4 billets about 3 feet long. these will dry for spindle use in about 2 years.

I reccomend turn it now and dry your turning
Al

 

[john lucas]

I do like Al. I either rough turn it or I cut it down to spindle sizes, seal the ends and let it sit. A 12x12x4 block will take quite a while to dry and you will probably lose it to checking if you set it up.

 

[Thomas Stegall]

I agree, use it now or loose it later to checking. If you can't use it now, do everything you can to retard the drying process.

 

[Odie]

Okay I pick up some cherry today, large chunks 12"X12"X4 1/2" is just one of them. the others, though smaller, are not to far off. All 3 are between 30% and 35% moisture. Not wanting to turn them right now, I am just wondering, how many Years will I have to wait for them to get a bit dryer. Less than 10% I assume will be ideal since I reside in Michigan.
Sure I could dry it out via the oven or do a DNA bath... But I am Patient.

Thanks in advance

Something that big and thick will take several years to dry. As others have mentioned, think seriously about roughing out a bowl, resealing, and drying from there. It's what most turners do, because not many of us want to wait that long to dry our wood.

Anything over 30% MC is very wet, and you could lose half that moisture content in 60 days, by roughing your bowl first.

Just wondering......is there some special reason why you would rather not rough the bowl, then dry?

Depending on how you do it, you could be finish turning within 6mo, but it usually takes me a bit longer than your average turner. If your average turner is finish turning in 6mo, I will probably take 8-10mo for the same roughed bowl. This is because I do try to dry roughed bowls as slow as possible, while doing what I can to speed things up.......just realized how crazy that sounds, but roughing a bowl cuts out 60-80% of the drying time over a solid block of wood. I seal the entire roughout, not just endgrain, or in bags......so, there I do what I can to slow down the process for the roughout. My success rate is higher than your average turner, because of my methods of slowing down the drying rate of roughed bowls means less cracks. After the bowl is roughed.......THERE is the time to apply your desire for patience!

Keep in mind, also, that different species, and even different blocks of wood that are the same species will dry at different rates. Cherry is fairly dense wood, and will take longer than something that is less dense, like ash......and less time than something that is very dense, like cocobolo, or bocote.

You might also want to think about getting yourself a digital postal scale. Moisture meters are good for determining initial MC, but not that good for knowing just when your roughed bowl (or block of wood, in your case) has reached stabilization. A scale, by using a measurement of weight over a given element of time, gives you an exact definition of that stability, whereas the meter isn't as exact. This will be obvious to you when you realize the readings will vary, depending on prong location......but, weight is a consistent measurement of an entire block of wood.......

ooc

 

[hughie]

[

Something that big and thick will take several years to dry. As others have mentioned, think seriously about roughing out a bowl, resealing, and drying from there. It's what most turners do, because not many of us want to wait that long to dry our wood.

Absolutely, drying slabs its 1 year per inch of thickness plus one year. A cube? Hmm, slice it up into smaller blanks or rough turn it now.

 

[MichaelMouse]

[

Absolutely, drying slabs its 1 year per inch of thickness plus one year. A cube? Hmm, slice it up into smaller blanks or rough turn it now.

How did that foolishness make its way down under? Inch per year pertains to hardwood planks in New England barns. Reality is significantly different, like ~100 summer days to 15% in the US midwest.

Since we modify the environment and often bring the wood indoors to work it, it's even less meaningful now. For instance, 4/4 cherry felled in February, sawed in May, reaches ~8% in my basement by December. In February it's 6% or less. If I don't bring it into the humidity-controlled area of the shop, it climbs back over 10% in the summer.

 

[Odie]

To give the forum reader an idea of how weight loss is an indicator of moisture content and stabilization, here are my weight measurements of a spalted Maple bowl that measured 10 1/4" diameter (bandsawed round) by 3" thick.....in its unseasoned, block form.

It took me one year to reach stabilization of the moisture content, and I make that determination when the monthly weighings show no weight loss for three consecutive months. (This means that I actually reached moisture content stabilization in 10 months, but it took two more weighings to confirm it.)

The block of wood (in the round) was initially rated at 24 percent moisture content (MC) by using my Lignomat mini ligno E moisture meter.

After roughing out the bowl, I immediately wax emulsion anchorsealed the entire bowl (nothing left uncoated), and this is the way it remained for the entire time, up until I remounted it for final finish turning.

I normally use the standardized formula of roughing a bowl to a wall thickness of 1/10th the diameter.......so, at 10 1/4" in diameter, this one was roughed to approximately 1" in thickness. This isn't a hard-fast rule, but only a generalized method of getting the best seasoning results. The wall thickness is one aspect of seasoning bowls where you will have complete control over the rate which you will allow your bowl to dry. The thinner the roughed bowl, the faster it will reach stabilization......thicker will take longer. The tendency for warping and/or cracking will be greater with the thinner roughed bowls, as well.........but this will be entirely dependent on your individual "game plan", grain characteristics, and species. I don't normally rough turn to thinner than recommended, but I have been known to do this to accomodate some aspect of shape, flaws, grain and species for a specific bowl.

I live in Montana. Roughed bowls are seasoned in my well insulated and heated shop. Shop remains at about 40-50 degrees during the fall and winter months, except when I am physically present. (A small ceramic heater is left on 24/7 during these months of the year.) During those times I'm in my shop, it is about 70 degrees when heated to my comfort level. It usually doesn't get over about 75-80 degrees in my shop during summer months, even when outside temperatures are higher. Roughed and anchorsealed bowls are stored at eye level in my shop, but this is because the available storage area doesn't permit me to store them on the floor. By storing at floor level, the temperatures will be consistently a little cooler......and more desirable for an even slower rate of moisture content loss. Since I keep my shop at temperatures lower than most turners would, I'm probably getting similar results when compared to someone who keeps their shop at higher temperatures, but stores seasoning bowls on the floor. (All other factors being equal.).......or lives in warmer climates, like in the southern states.

As you can see from the weights logged below, a lot of the moisture content is lost during the first few months of seasoning. Weight loss is increasingly less, month by month, until stabilization occurs.

11/04/2009.....bowl roughed and anchorsealed. 24 percent MC, metered
11/05/2009.....1080 grams (initial weighing)
12/02/2009.....1010 grams (lost 70 gm)
01/02/2010.......975 grams (lost 35 gm)
02/04/2010.......955 grams (lost 20 gm)
03/02/2010.......940 grams (lost 15 gm)
04/06/2010.......925 grams (lost 15 gm)
05/05/2010.......910 grams (lost 15 gm)
06/04/2010.......905 grams (lost 05 gm)
07/03/2010.......900 grams (lost 05 gm)
08/03/2010.......885 grams (lost 15 gm)
09/04/2010.......880 grams (lost 05 gm)
10/06/2010.......880 grams (lost zero)
11/01/2010.......880 grams (lost zero)

This bowl finished turned in February of 2011 as a food safe salad bowl.

ooc

(The bowl on the postal scale is not the bowl used as the subject of this posting.......was just something I had handy when I took the photo several years ago. It looks like the bowl in the photo is in the process of being finished turned, anyway.)

 

[MichaelMouse]

Temperature is not what you pay attention to, OD. It's relative humidity. Makes your data, while interesting, inapplicable to the actual drying process.

Not to mention you've easily tripled your cure time by slathering the entire piece, inside and out, with wax. The Wood Handbook, free at the FPL site, will explain how and why relative humidity affects wood.

 

[Odie]

Temperature is not what you pay attention to, OD. It's relative humidity. Makes your data, while interesting, inapplicable to the actual drying process.

Not to mention you've easily tripled your cure time by slathering the entire piece, inside and out, with wax. The Wood Handbook, free at the FPL site, will explain how and why relative humidity affects wood.

What works.........works.......MM 😀


Temperature is something that does effect the process, and easy to manipulate........The relative humidity in our particular climate isn't that easy to manipulate, but it's unquestionably a factor that one can adjust, as you do. The sticking point of your whole line of thinking, is you have no control over the relative humidity anywhere but in your own controlled area of influence. Do you think the 8 percent MC you get in your basement will be maintained in your shop, in your living room, in someone else's living room, in another state? What is important is not the number percent of moisture content, but the stabilization of that moisture content prior to making the decision to finish turn it. That number will be a relatively low number, but not a constant. I've found bowls to stabilize anywhere from 6 percent up to about 10-12 percent.......but, for the most part, I don't even bother to check with the moisture meter anymore, because the weight readings don't give a false indication about the status of whether the MC has stabilized.

It's obvious that you believe your thinking is indisputable, but just like your "volcano bowls" and excessively slow turning speeds, which not everyone agrees will be conducive to the best and cleanest cut.....your thinking isn't without good cause for warranted skepticism from those who consider your techniques from an equally experienced perspective.

It's surely ok to express your opinion on things, but you have a habit of being a little too abrasive in the way you deal with other people on this forum. Your post to Hughie is a good example of this.......because you know, he is right about the 1" per year + 1 year simplistic principle of estimating the time to dry solid blocks of wood.

How did that foolishness make its way down under?

Woodturning is something that is full of opinions......we all have them.....and yours is welcome at any time. My suggestion to you is to think a little about this......allow others their opinions, without becoming someone who ultimately stifles forum discussion and input.

ooc

 

[Thomas Stegall]

drying wood

It seems to me that temperature could be relavant, as temperature directly effects relative humidity, hense the term "relative". 90% relative humidity at 80 degrees does not have the same moisture content as the same as 90% relative humidity at 40 degrees. And, the temperature of a piece of wood will follow that of the air around it. When we consider that higher temperatures also increase the rate of evaporation, I can't imagine how temperatures would not play at least some role in the drying process?

 

[john lucas]

On top of all the I've also read ( I think it was from the forestry service but don't remember for sure) that in log form the wood will start drying at the normal fairly rapid rate and then slow down sometimes almost coming to a stop. so an 8" log could possibly take 10 to 12 years to dry.
In my own shop the 1" per inch varies by species just as easily as time of year.

 

[MichaelMouse]

It seems to me that temperature could be relavant, as temperature directly effects relative humidity, hense the term "relative". 90% relative humidity at 80 degrees does not have the same moisture content as the same as 90% relative humidity at 40 degrees. And, the temperature of a piece of wood will follow that of the air around it. When we consider that higher temperatures also increase the rate of evaporation, I can't imagine how temperatures would not play at least some role in the drying process?

Nope, back to the books for something that is, not seems relevant. (No, it does not depend on what you think is is.) You can have 90% relative humidity at any temperature from 0 to 100C. More to the point, at any temperature a human can tolerate for any time (04-40C) you won't have more than a percentage point's difference in EMC for any RH within that range.

Take the time to download and read Ch 4 of the work cited, or to read the chapter on wood and water in Hoadley's book. If you know why something happens you'll have a far better shot at making it happen. OD's assertions notwithstanding, science is the place to start.

 

[KellyDunn]

Odi, I have been a production turner for a very long time. i will agree that coating both inside and out is a waste of your time. Just the outside. On side grain not the bottom. End grain whole outside. If it says 8% in your basement I would say you are ready. And I disagree with just using a scale. You know I am a fan of low tech kilns from old fridges. But its very wet where I live in Hawaii. Your basement sounds great. Wont work for me. If I dont kiln dry my meter may say 12% but when I turn I still get some water and steam. Its called bound cellular moisture. Here only a kiln will take care of it. 3 miles from me is the desert. I would not need my kiln if I turned there. I would however need to be much more careful in my coating blanks to prevent splitting. One surface though. But would have to get on it instead of coating roughed out work at the end of a rough out day. So your right that no one way will work for all of us. But save yourself a lot of time and just coat one surface. I am an expert at this. Just in case you wondered.

 

[MichaelMouse]

On top of all the I've also read ( I think it was from the forestry service but don't remember for sure) that in log form the wood will start drying at the normal fairly rapid rate and then slow down sometimes almost coming to a stop. so an 8" log could possibly take 10 to 12 years to dry.
In my own shop the 1" per inch varies by species just as easily as time of year.

It could take forever to dry, but it will find equilibrium with the RH in which it resides, which is all it ever can do. Lower the RH and the moisture content will fall, raise, and it will rise. There is a bit of a deviation - sorption hysteresis - for sucessive cycles, but that is so small it can be ignored for practical purposes.

The reason the 1" business is silly with bowl shapes is that wood loses moisture through end grain 10-12 times as rapidly as through face grain, and even a bit slower through quarter. When you take the middle out, you set up a situation where face or quarter ceases to be important in the drying process. The rate is all determined by the end grain. A look at your firewood should demonstrate how far and fast end checks - a sign of drying - occur in any of your common species. Now consider that your two open ends are no farther from open air than an inch or two in almost any bowl rough, and you'll realize why a couple-three months will normally suffice to cure to EMCs of 10-15%. Unless you set up an environment of elevated RH by coating or otherwise restricting the rate of loss. Bark is more or less the same as a cardboard box, unless you're talking something like birch.

 

[Odie]

We do have opinions here........

Well, the scale doesn't lie......

Weight loss, is water loss.

When weight stabilizes, the moisture content stabilizes.

When the MC in wood stabilizes to any RH, it will seek a re-adjustment
when moved to any different RH.

Might as well stabilize to the climate you are in, because you are not guaranteed a change in environment will not effect your bowl, but if there is a difference in RH between your basement and your shop, or home, or final destination of your bowl, the wood will seek an adjustment.

BTW: KellyDunn.........I'm not a production turner, but next year will mark thirty years of turning for me.......not that time based experience means anything......but, it seems to be important to you (or, you seem to make the case for your own credentials). However, you are right that most roughed bowls won't make much difference if the entire surface is not coated, but it's a fact that rate of water loss (slow vs slower) does effect some bowls to the point of cracking and excessive warping, when a slower rate of seasoning would have been more successful. It would be hard to know exactly which ones can be dried more quickly (unless, from prior experience, they were known to have similar grain, from the same tree, and/or species), so, I prefer to do what I know will have a higher rate of success, and coat the entire roughed bowl.

As I said before.......whatever works.......works! .....and weight is what gives definite answers. It gives an indication of the MC, for an entire piece of wood......not just the surface at any given point. Moisture meters are not as dependable for consistent and accurate readings of the entire interrior of a roughed bowl, or block of wood.

When we consider that higher temperatures also increase the rate of evaporation, I can't imagine how temperatures would not play at least some role in the drying process?

Thomas is correct about this. Sometimes it amazes me how simple truths like this get bypassed in the discussion. A lower MC, means only one thing, less water content. Weight loss is water loss......and water loss is the result of evaporation. The rate of, or speed of evaporation is directly influenced by the ambient temperature. A lower temperature will result in slower rates of evaporation over a higher temperature......connect the dots.






ooc

 

[MichaelMouse]

We do have opinions here........

The rate of, or speed of evaporation is directly influenced by the ambient temperature. A lower temperature will result in slower rates of evaporation over a higher temperature......connect the dots.

Well, that is an opinion. It is also incorrect, as the mass of data available and referenced substantiates. The rate of evaporation depends, first and foremost, on the ability of the air to take on more moisture. If it's saturated, nothing leaves. Check the weather. At the dewpoint, there is no loss. One degree below there is precipitation.

The second greatest influence is circulation. Since the air close to the surface is more saturated, we can help ourselves by moving it away and bringing in less-saturated air to carry the new burden. Coating, or otherwise containing the air can slow the process of evaporation. Plastic bagging will stop it altogether when the relative humidity reaches 100% in the confined space.

Now if we take a quantity of air containing a defined quantity of water - called the absolute humidity for those who would rather learn than opine - and warm that air, we will increase its carry capacity, lowering its relative humidity. We may expect an increased rate of drying over cooler air containing the same absolute amount of moisture. Which brings us full circle to the truth that relative humidity is the determinant of drying rate.

Oh yes, evaporation lowers the temperature.

 

[Odie]

Well, that is an opinion. It is also incorrect, as the mass of data available and referenced substantiates. The rate of evaporation depends, first and foremost, on the ability of the air to take on more moisture. If it's saturated, nothing leaves. Check the weather. At the dewpoint, there is no loss. One degree below there is precipitation.

The second greatest influence is circulation. Since the air close to the surface is more saturated, we can help ourselves by moving it away and bringing in less-saturated air to carry the new burden. Coating, or otherwise containing the air can slow the process of evaporation. Plastic bagging will stop it altogether when the relative humidity reaches 100% in the confined space.

Now if we take a quantity of air containing a defined quantity of water - called the absolute humidity for those who would rather learn than opine - and warm that air, we will increase its carry capacity, lowering its relative humidity. We may expect an increased rate of drying over cooler air containing the same absolute amount of moisture. Which brings us full circle to the truth that relative humidity is the determinant of drying rate.

Oh yes, evaporation lowers the temperature.

😀 Sure it's correct, MM..........😀

.......and, the reason it's correct it when you apply more heat, the drying rate increases......it's a very simple concept, really.......don't know why you are incapable of understanding that. If you are air drying rough outs in a room of any given RH, at 50 degrees, the rate of drying will be slower than the same rough outs in the same room, at the same RH, at 75 degrees. If you take it to an extreme, and put your wood in a kiln, oven, or microwave, all you are doing is applying heat, which reduces the MC, and the amount of time it takes to achieve that rate of moisture loss.

Yes, you are correct, when you say:

The rate of evaporation depends, first and foremost, on the ability of the air to take on more moisture.

.....but, what you are failing to mention is when the surrounding air is no longer able to take on any more moisture, this IS the goal.......and, it's called stabilization! 😉

I will also enthusiastically agree that air circulation is a factor in air-drying roughed bowls. This is why most (not all) of us do not stack them one inside another. I do what many other turners do......use staves, or "stickers" between the bowls to allow for more air circulation.

Oh yes, evaporation lowers the temperature.

Now, now, MM........you are "reaching" here........If you're talking about sweat on your brow, or tying a wet rag around your neck, sure you would be correct about that......but, if we are talking about losing a cup of water from a chunk of wood over the period of many months, you are insulting the intelligence of the readers of this forum. 🙄



ooc

 

[KellyDunn]

Odie, you are right the scales dont lie. They do tell you when the water in the bowl matches the ambient air content. And you are more than welcome to continue what works for you with no grief from me. But for those that want to understand the nature of drying wood I one more time will state the goal is to remove bound cellular moisture. That takes a kiln or very dry climate. Also I want the bowl to warp all its going to do in the drying process instead of while I am turning it. Excessive warping happens in what I call unstable woods or in areas of crotches or bends in a branch. You just get to know what woods are going to do what. But its wood so I try not to be upset when I get surprised.
One thing I have not stated is how thick I leave my blanks. Smaller bowls maybe 1/2 inch wall thickness. Up to maybe 12 inches about 3/4 to an inch.Larger maybe a bit more. The thinner they are the more my success rate is. I do have to take into consideration a wood that really moves. So I leave those thicker.
One Arizona turner I know built one of my fridge kilns. He says with a low wattage bulb it actually slows down his drying and he has a much better success rate. Actually I got the kiln idea from another turner about 25 years ago. He said it was a secret. But I teach that in a class I call roughout and curing. I started out using a scale. Just does not work here for telling you when its really time to finish turn. The air dry guys here give it three months. They have shelfs that let air and the trade winds blow around the work.
And I admit what I do works for me as a tropical turner.
Back in 66 the first time I turned drying was never mentioned. In 79 here in Hawaii my first real teacher just turned really hard local woods and never talked about drying. He also did pretty small items. Mostly from Kiawe(mesquite). It wasnt until 85 when I went to Provo that Nick Cook, Richard Raffan and the rest of a great bunch of turners really discussed curing and drying. I went full time in 89 and Jack Straka mentored me in his processes. I started kiln drying in 90. I now have a consistent product. But I always want to learn more.
I bet if we stood at a lathe together we each would learn something from the other. And that is the meat and potatoes of why we all hang out together as woodturners.

 

[MichaelMouse]

But for those that want to understand the nature of drying wood I one more time will state the goal is to remove bound cellular moisture. That takes a kiln or very dry climate. Also I want the bowl to warp all its going to do in the drying process instead of while I am turning it. Excessive warping happens in what I call unstable woods or in areas of crotches or bends in a branch. You just get to know what woods are going to do what. But its wood so I try not to be upset when I get surprised.

Bound moisture will remove itself as the relative humidity permits. Wood will also re-bind moisture as the relative humidity rises. It's always trying to do this, which is why it is referred to as an hygroscopic material. You have noticed that wood you have dried below the EMC gains weight when you put it out in the open air, right? Once again, works like Hoadley and the free FPL publication have graphed this seasonal phenomenon as it happens in Wisconsin.

Thinner walls are lower risk against splits because the wood contracts upon itself. More wood, greater total contraction, though the ratio is pretty constant. They cure faster, too. I use about 7.5% of diameter unless I'm undecided and may want a restyle, but anything over about an inch increases risk of wall splits, even with similar conformation.

 

[Odie]

Odie, you are right the scales dont lie. They do tell you when the water in the bowl matches the ambient air content. And you are more than welcome to continue what works for you with no grief from me. But for those that want to understand the nature of drying wood I one more time will state the goal is to remove bound cellular moisture. That takes a kiln or very dry climate. Also I want the bowl to warp all its going to do in the drying process instead of while I am turning it. Excessive warping happens in what I call unstable woods or in areas of crotches or bends in a branch. You just get to know what woods are going to do what. But its wood so I try not to be upset when I get surprised.
One thing I have not stated is how thick I leave my blanks. Smaller bowls maybe 1/2 inch wall thickness. Up to maybe 12 inches about 3/4 to an inch.Larger maybe a bit more. The thinner they are the more my success rate is. I do have to take into consideration a wood that really moves. So I leave those thicker.
One Arizona turner I know built one of my fridge kilns. He says with a low wattage bulb it actually slows down his drying and he has a much better success rate. Actually I got the kiln idea from another turner about 25 years ago. He said it was a secret. But I teach that in a class I call roughout and curing. I started out using a scale. Just does not work here for telling you when its really time to finish turn. The air dry guys here give it three months. They have shelfs that let air and the trade winds blow around the work.
And I admit what I do works for me as a tropical turner.
Back in 66 the first time I turned drying was never mentioned. In 79 here in Hawaii my first real teacher just turned really hard local woods and never talked about drying. He also did pretty small items. Mostly from Kiawe(mesquite). It wasnt until 85 when I went to Provo that Nick Cook, Richard Raffan and the rest of a great bunch of turners really discussed curing and drying. I went full time in 89 and Jack Straka mentored me in his processes. I started kiln drying in 90. I now have a consistent product. But I always want to learn more.
I bet if we stood at a lathe together we each would learn something from the other. And that is the meat and potatoes of why we all hang out together as woodturners.

Good post, KellyDunn.......

At least you seem to be willing to realize there is no one method that is applicable. I have no doubt your climate and the woods you use have caused you to evolve to a method that works best for you......and, the same applies to me, as my success rate may not be 100 percent, it's very noteworthy and probably close to 98-99 percent.

I'm glad you said that about standing together at the lathe and learning from each other. You bet that's why I'm here. I may know a few things that I can pass along to other turners, but this forum has been immensely helpful to me. I have learned things from most everyone here, and have even gotten fresh and new ideas from beginning turners!

It's very disappointing and unfortunate that some people who hang out on this forum, just like in other forums I have participated in, seem to be desirous of being the forum's "all knowing" master. I guess this "pecking order" kind of thing is just a product of human nature, but, in the end, these people are a detriment to a forum where everyone feels free to participate.....and everyone benefits. What we want here, is a free flow of information and thought.......not some kind of club for those who see this forum as a means of self promotion. 😀

Later, Kelly........

ooc

 

[KellyDunn]

M Mouse,
Its been a long time since I studied the concepts of drying wood. So I can not put my hands on the manual. But if memory serves me, no, moisture will not re-bind on the cellular level.Its like a little cube holding water. The shell has to be broken so to speak for the water to leave. Its true a piece of wood will regain to ambient air moisture content. But after the bound moisture is gone the wood will move faster towards whatever the weather is doing. And its true given enough time the wood will dry to whatever ambient. For me my humidity stays over 80% most of the time. A few miles away in the desert its bone dry and wood laying on the ground will meter out at 6%. A piece air dried years here can be 12 to 18%. And if I turn it without it going though the kiln it will still pop out some moisture and move a whole bunch during the turning.
I am not a wood scientist. If you can find the manual from those experts to prove my memory wrong you get an apology. Until then I stand by my statements on bound cellular moisture.

 

[MichaelMouse]

Lay on for free. Or prepaid, at least. http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p Wealth of good experimentally-derived scientific information there, including the information on the difference between bound and unbound water, and the hygroscopic nature of wood. Unbound moisture is contained within the cell walls and in the vessels. Bound moisture is hydrogen-bonded to the cellulose itself, and seems saturated in the vicinity of 30% moisture content by weight. It's referred to as the Fiber Saturation Point, and the place where the fibers begin to contract on their way down. Trouble starts there if we're not careful.

Check table 4-1 and Fig 4-2 and the accompanying verbage on adsorbtion/desorbtion hysteresis. Note also the difference between ad and absorbed moisture. First gets bound, second stays free.

If you develop heat when you turn and sand, you're effectively lowering the relative humidity and drying the wood. Why we don't want to press too hard in either operation. As the wood dries at the surface, checks can open. No surprise there, since we know it is the same process experienced in initial drying. That's the great thing about operating on science rather than opinion - like the serenity prayer, we have the wisdom to know the difference between what we can effect and what must happen.

I make a desert in my basement every winter. Air at -10 outdoors can't hold much absolute moisture at all, even though the RH is high. When I warm it to 70, the relative humidity plummets. My lumber goes to 4% and below in winter. Summers, it's 12% unless I condition it in my humidity-controlled shop. Since the wood gains dimension with moisture, I build loose in winter, tight in summer, and always allow for the direction and extent of movement science tells me must happen.

 

[Chris Fontana]

Dew Point

I amateur woodworker (stress amateur) who really enjoys turning bowls. I am normally a "lurker" on this site since I consider those of you that post quite a bit "the pros from Dover" However, today as I am reading through the posts I find a raging debate that touches an area that I have some experience in. I am a meteorologist with over 40 year experience in "Fire or Forestry Weather" most of it in Northern California. All of you are right to a point, when you discuss temperature, Relative Humidity, bound and free water...etc. The drying times will vary depending on climate or weather...."weather is what we forecast and climate is what we get". The most important thing to monitor for drying is Dew Point. Dew point is the one element that remains constant in a given airmass. I would recommend that you download the table from this site that applies to your elevation. http://www.wrh.noaa.gov/sto/rhtbl.php Lets say it's winter and the outside air temperature is 30 degrees and the humidity is 65% this means the dew point is approximately 20 degrees. Now when you bring that air into your shop or house and warm it to 70 degrees the dew point will remain 20 and the humidity will drop to about 15%. That's its called Relative Humidity because it is relative to the temperature. The opposite happens in the summer when you cool the air...unless you use a swamp cooler. Current dew point values are easy to find on line from several sources...airports or fire weather offices.

Another interesting resource is what is called the 1000 hr fuel moisture. This is the "dead fuel" moisture for wood 3 to 6 inches in diameter. It monitored across the U.S. Here is a link to the sites for Northern California. http://gacc.nifc.gov/oncc/predictive/fuels_fire-danger/psac/thousand/index.htm These are available for sites across the U.S. This shows how fast drying occurs in a given area of the U.S.

Live fuel moisture is different but there are sites that track that. I know this isn't totally applicable to the discussion but I think these are some things that need to be considered. I have been doing my own experiments with drying in the north valley climate and things are faster than 1 inch per year. Last winter I got a couple of chunks of a big valley oak that blew over. I cut the pith out, sealed it and left it my shop. Four weeks ago I turned a small bowl 4 inch diameter and brought it in the house. I have been weighing it weekly to see how much it dries started out and 18 1/2 ounces and is now holding at about 15 without any distortion or cracking.

 

[Jim Keenan]

Good post, KellyDunn.......


It's very disappointing and unfortunate that some people who hang out on this forum, just like in other forums I have participated in, seem to be desirous of being the forum's "all knowing" master. I guess this "pecking order" kind of thing is just a product of human nature, but, in the end, these people are a detriment to a forum where everyone feels free to participate.....and everyone benefits. What we want here, is a free flow of information and thought.......not some kind of club for those who see this forum as a means of self promotion. 😀

Later, Kelly........

ooc

It appears those same people seem to lack insight.

 

[Odie]

As you can see from the weights logged below, a lot of the moisture content is lost during the first few months of seasoning. Weight loss is increasingly less, month by month, until stabilization occurs.

11/04/2009.....bowl roughed and anchorsealed. 24 percent MC, metered
11/05/2009.....1080 grams (initial weighing)
12/02/2009.....1010 grams (lost 70 gm)
01/02/2010.......975 grams (lost 35 gm)
02/04/2010.......955 grams (lost 20 gm)
03/02/2010.......940 grams (lost 15 gm)
04/06/2010.......925 grams (lost 15 gm)
05/05/2010.......910 grams (lost 15 gm)
06/04/2010.......905 grams (lost 05 gm)
07/03/2010.......900 grams (lost 05 gm)
08/03/2010.......885 grams (lost 15 gm)
09/04/2010.......880 grams (lost 05 gm)
10/06/2010.......880 grams (lost zero)
11/01/2010.......880 grams (lost zero)

This bowl finished turned in February of 2011 as a food safe salad bowl.

ooc

In a PM, someone pointed out the recorded weight on 08/03/2010 had an abnormal weight loss of 15grams, and doesn't reflect my statement of a steady weight loss throughout the drying process. Most do, but sometimes a small variance does occur. I can recall one or two roughed/sealed bowls actually showing a slight increase of weight over a previous weighing.......but, the bottom line is: ALL roughed bowls eventually stabilize in weight, and when that happens, the process is completed when 3 consecutive months register the same weight.

Here is another bowl that I just completed:

Bowl number 675, Spalted Hackberry, 10 1/4" x 3 3/8" , took 13 months to stabilize, 2 months to confirm.

08/24/2009.....bowl roughed and anchorsealed, 36 percent MC, metered
08/25/2009.....1355 grams (initial weight)
09/01/2009.....1280 grams (lost 75 gm)
10/01/2009.....1040 grams (lost 40 gm)
11/01/2009.......985 grams (lost 55 gm)
12/02/2009.......960 grams (lost 25 gm)
01/02/2010.......955 grams (lost 05 gm)
02/04/2010.......950 grams (lost 05 gm)
03/02/2010.......950 grams (no change)
04/06/2010.......945 grams (lost 05 gm)
05/05/2010.......935 grams (lost 05 gm)
06/04/2010.......940 grams (gained 05 gm) (no explanation for this)
07/03/2010.......935 grams (lost 05 gm)
08/03/2010.......925 grams (lost 10 gm)
09/04/2010.......920 grams (lost 05 gm)
10/06/2010.......920 grams (lost zero)
11/01/2010.......920 grams (lost zero)

ALL bowls stabilize, and that's the time to finish turn........


-----------------------------------------------

One added note: How many roughed bowls should a turner have on hand? This all depends on what your production rate is. If you average 50 bowls per year, like I do......that's about how many bowls you should be seasoning at any given time. The more, the better.

If you production turn, the number will be much higher. I believe I saw a post from KellyDunn where he (she?) said he had near a thousand bowls being seasoned. For that many, his production rate will obviously be much higher than mine is.......

ooc

 

[MichaelMouse]

In a PM, someone pointed out the recorded weight on 08/03/2010 had an abnormal weight loss of 15grams, and doesn't reflect my statement of a steady weight loss throughout the drying process. Most do, but sometimes a small variance does occur. I can recall one or two roughed/sealed bowls actually showing a slight increase of weight over a previous weighing.......but, the bottom line is: ALL roughed bowls eventually stabilize in weight, and when that happens, the process is completed when 3 consecutive months register the same weight.

If you compared your fluctuations in weight with the hygrometer in your storage room you'd soon come to the same conclusion already developed for you in the FPL book. A couple weeks at higher humidity is certainly enough to move a few grams, even in a sealed bowl.

No surprise at the rapid loss of unbound water early on, followed by the slow loss of water bound in the sugars. Once again, merely confirmation of someone else's work. I've never devoted the time it would take to verify this, but based on spot observations, The Wood Handbook is correct in stating that contraction from loss of bound water is nearly linear. Means your piece was ready on 3/2 or thereabout as far as overall stability.

Cut a bowl you believe is dry, weigh, then leave it alone. See what happens after a damp or dry week. We can't stop nature, and without proper control, 3-5% annual swings (30gm) are easily possible.

 

[Odie]

If you compared your fluctuations in weight with the hygrometer in your storage room you'd soon come to the same conclusion already developed for you in the FPL book. A couple weeks at higher humidity is certainly enough to move a few grams, even in a sealed bowl.

No surprise at the rapid loss of unbound water early on, followed by the slow loss of water bound in the sugars. Once again, merely confirmation of someone else's work. I've never devoted the time it would take to verify this, but based on spot observations, The Wood Handbook is correct in stating that contraction from loss of bound water is nearly linear. Means your piece was ready on 3/2 or thereabout as far as overall stability.

Cut a bowl you believe is dry, weigh, then leave it alone. See what happens after a damp or dry week. We can't stop nature, and without proper control, 3-5% annual swings (30gm) are easily possible.

MM

When a bowl loses water content, it loses weight.....it's that simple. That physical property is measurable and positive means of determining stability.

There is no question that one's climate is a contributor to the results. There will be humidity fluctuations in any locale, and the hygrometer readings in your basement will lead to changes in the MC of any wood outside of that environment and humidity.......so, you would be best served to dry your wood in the environment it will be in, rather than artificially arrive at a MC that does not support it's environment.

Another person in a PM told me you were on his ignore list......and, I can see why, because you insist on reducing threads with a continual desire to argue the same points over and over again. Maybe you should make your point, and leave it at that. Or, you are welcome to start your own thread.........

ooc

 

[KellyDunn]

Odie, First name is James. But I was born when Kelly was a common name for guys. No more. And I finish turn a few hundred pieces a year. When my wife Linda and I worked together we did 7 to 800 a year. She sanded. I miss that. If you are interested in seeing what she put together during bad economic times check out www.dunngallerywoodart.com
And I do have around a thousand roughed out pieces on the shelves.
And if you are really curious www.kellydunnwoodturner.com and if you googled me you get several thousand hits. I tend to do demos under J.Kelly Dunn but for the forum its best to find me with just Kelly. J. Paul Fennell has no problem with the J. for him. He has used it for so long on forums folks just know.

 

[MichaelMouse]

Apologies, OD, I thought if you wrote you knew no reason for the gain that you might be interested in finding out. Apparently not.

For others who often express interest in the least amount of time to dry a piece, if you know the relative humidity where the the piece is stored, you can certainly feel safe in final turning when the piece declines less than one per cent per month, when the turning is an inch or less in thickness.

 

[Odie]

Apologies, OD, I thought if you wrote you knew no reason for the gain that you might be interested in finding out. Apparently not.

For others who often express interest in the least amount of time to dry a piece, if you know the relative humidity where the the piece is stored, you can certainly feel safe in final turning when the piece declines less than one per cent per month, when the turning is an inch or less in thickness.

MM......If you'll check, there are two examples there. Both roughed bowls were weighed on the same date, and were stored in the same location. The weight was taken in the month of June. This is a time of that year when humidity was at it's lowest.......so, I don't think you can conclude the humidity is the reason for a 5 gram increase in weight for one bowl while everything else registered a loss. There are other factors at play, here.......heat, species, thickness of wood, how well the anchorseal prevented the moisture escape, physical properties and grain of a specific piece of wood, the MC of that particular piece of wood in that particular month of the seasoning process, the accuracy of the scale itself, etc. This is not to say humidity isn't a factor that may, or may not have influenced the reading, but I'd say from what is known about the other bowls that were weighed at the same time, and stored in the same location, it's not that likely.

Whatever the reasons for a one time, during one month, fluctuation in weight from the norm......it really isn't that important, because the weight and when stabilization occurs is the indicator of when a bowl is ready for final turning. As I've indicated before, this is not to say there aren't other methods of determining stabilization, but weight/time is one method that does work, and is reliable and repeatable.

ooc

 

[Odie]

Odie, First name is James. But I was born when Kelly was a common name for guys. No more. And I finish turn a few hundred pieces a year. When my wife Linda and I worked together we did 7 to 800 a year. She sanded. I miss that. If you are interested in seeing what she put together during bad economic times check out www.dunngallerywoodart.com
And I do have around a thousand roughed out pieces on the shelves.
And if you are really curious www.kellydunnwoodturner.com and if you googled me you get several thousand hits. I tend to do demos under J.Kelly Dunn but for the forum its best to find me with just Kelly. J. Paul Fennell has no problem with the J. for him. He has used it for so long on forums folks just know.

Hey, some nice things there, Kelly........

......some nice things from some of the other artists in the gallery, too!

Sorry about the name confusion, but I'm sure you are aware that the name Kelly doesn't conform to it's male roots, and hasn't for quite awhile. I think it was the TV series "Father Knows Best", where the daughter was named Kelly (IIRC)......that was the turning point on the traditional gender applications of the name.

ooc

 

[Nate Hawkes]

What works.........works.......MM 😀


Temperature is something that does effect the process, and easy to manipulate........The relative humidity in our particular climate isn't that easy to manipulate, but it's unquestionably a factor that one can adjust, as you do. The sticking point of your whole line of thinking, is you have no control over the relative humidity anywhere but in your own controlled area of influence. Do you think the 8 percent MC you get in your basement will be maintained in your shop, in your living room, in someone else's living room, in another state? What is important is not the number percent of moisture content, but the stabilization of that moisture content prior to making the decision to finish turn it. That number will be a relatively low number, but not a constant. I've found bowls to stabilize anywhere from 6 percent up to about 10-12 percent.......but, for the most part, I don't even bother to check with the moisture meter anymore, because the weight readings don't give a false indication about the status of whether the MC has stabilized.

It's obvious that you believe your thinking is indisputable, but just like your "volcano bowls" and excessively slow turning speeds, which not everyone agrees will be conducive to the best and cleanest cut.....your thinking isn't without good cause for warranted skepticism from those who consider your techniques from an equally experienced perspective.

It's surely ok to express your opinion on things, but you have a habit of being a little too abrasive in the way you deal with other people on this forum. Your post to Hughie is a good example of this.......because you know, he is right about the 1" per year + 1 year simplistic principle of estimating the time to dry solid blocks of wood.



Woodturning is something that is full of opinions......we all have them.....and yours is welcome at any time. My suggestion to you is to think a little about this......allow others their opinions, without becoming someone who ultimately stifles forum discussion and input.

ooc

This is one of the most refreshing posts I've read on the AAW forum. Thanks Odie!

 

[Nate Hawkes]

Odie, First name is James. But I was born when Kelly was a common name for guys. No more. And I finish turn a few hundred pieces a year. When my wife Linda and I worked together we did 7 to 800 a year. She sanded. I miss that. If you are interested in seeing what she put together during bad economic times check out www.dunngallerywoodart.com
And I do have around a thousand roughed out pieces on the shelves.
And if you are really curious www.kellydunnwoodturner.com and if you googled me you get several thousand hits. I tend to do demos under J.Kelly Dunn but for the forum its best to find me with just Kelly. J. Paul Fennell has no problem with the J. for him. He has used it for so long on forums folks just know.

Kelly, your website is great!! And, I know at least a couple guys named Kelly, by the way!

 

[KellyDunn]

Nate, thanks. My wife linda takes care of the website. She likes to do educational stuff on Hawaiian grown trees alot. So tree of the month changes. And she adds things when we do a photo shoot and takes things off as they sell. so it does change alot.

 

[John Torchick]

I just clicked on this thread out of curiosity. How does a DIY refrigerator/kiln figure into the drying time here?
I'm thinking I might not live long enough to turn a large piece of wood! I'm at the age where I don't buy green bananas!
Thanks for the info.

 

[Thomas Stegall]

Kelly,

You mentioned that your wife did the sanding and that you missed it. I would be happy to "help" you return to your former sanding pleasure 🙂 I'll send some pieces your way.

 

[MichaelMouse]

Contains/controls airflow to control RH like bagging or boxing. You control the RH (if you gauge it) by opening or limiting your vents, or leave it to "good enough" with no monitor. Warming can decrease the RH while promoting convective action. If you get some of the soon-to-be-banned incandescent bulbs, you can use them as your heat source. Otherwise, one of the root heaters used for starting plants is a gentle source which won't promote overheating and excessive venting. I suppose you could work it like a regular kiln, building to saturation and releasing all at once, then repeating as you stage down, but most throw stuff in there and let things happen.

I fell into a deal on one of those tall fridges with the glass doors where they display/sell pop. Functional, but it only cools and dehumidifies to keep the product drinkable and visible. I set it to run for 30 minutes three times a day and stored my winter squash in it. They like it cool and dry. We ate squash late in March which we had put in first week of October, which is one reason why it will never become a "kiln," even though it would certainly do for one. Some folks swear by "freeze" drying for turnings, which uses the defrost cycles of a frost-free fridge to do the same thing.