Water is what we drink, moisture is what forms on our brow when we try to think of the difference.
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Got a free freezer... Now what?
- Thread starter Mark Hepburn
- Start date
Folks, there is zero difference between bound cellular moisture and water. Same thing.
I did not invent this stuff. I got it from a book on wood kilns. It was way to technical for me as it was aimed for professionals who dry thousands of board feet of timber. I only have a pile of years in my low tech kiln. But the same principals apply to all wood drying. I dry roughed bowls. Right now its 90% humidity outside. It works for me but I had to rely on a professional work to understand whats what. You dry it to fast and thats not good. Forget the term but a board that has been dried to fast looks and acts strange when worked. I dont think you can dry to slow. Anyway it can get very technical if you want to research it.
I did not invent this stuff. I got it from a book on wood kilns. It was way to technical for me as it was aimed for professionals who dry thousands of board feet of timber. I only have a pile of years in my low tech kiln. But the same principals apply to all wood drying. I dry roughed bowls. Right now its 90% humidity outside. It works for me but I had to rely on a professional work to understand whats what. You dry it to fast and thats not good. Forget the term but a board that has been dried to fast looks and acts strange when worked. I dont think you can dry to slow. Anyway it can get very technical if you want to research it.
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Is the term that you are thinking of known as "honeycombing"? Honeycombing is basically an extreme case of "case hardening" which is the result of drying wood too fast. Case hardening is the breakdown of bonds between fibers at the microscopic level. Honeycombing goes further and creates very visible cracks in the wood. Another type of defect is "surface checking".
odie
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There is the crux of the matter, right there....^
Kelly Dunn's circumstances, due to his location, are different than most the rest of us.....so a low-tech kiln makes sense to his needs.
The truth is, most of us live in locations that are conducive to air-drying our own roughed bowls.....and naturally air-drying them makes perfect sense. I believe Kelly Dunn is correct, when he says you can't dry too slow......but, you can certainly dry too fast! The only realistic way to make air-drying a viable method, is to have a stockpile of roughed bowls on hand.....that way, we have plenty of projects ready to go on our lathes, at any given time.
Seems to me, the single solitary reason most of us would want a "refrigerator kiln" is simply to reduce the time element.....and, that need is insignificant when considering the problematic results of drying too fast. For me, it's not so much that the wood "acts strange", as Kelly Dunn puts it. That could be, but, the ultimate purpose is to end up with a stabilized MC without cracks and checks.
ko
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I do my rough out drying in paper bags and hollow forms in a box.
Both provide a humidity chamber and allow some moister/water to escape the container.
If I put s rough out in a paper bag and put that bag in front of a fan the bag dries causing the moisture to leave the bag faster and the piece will likely crack.
The high humidity in the bag or box keep the short grain side of the vessel hydrated so it does not dry faster than the long grain which is supplying moisture.
The box is simple, rinse the piece with water to be sure the endgrain is wet, towel dry, one day with the flaps closed,
one day with the flaps open, one day on the self, ready to sand and finish.
Most of my HF would likely dry quite well without having the box. It may be like a security blanket. The box requires the labor of closing the flaps and opening the flaps.
A kiln has to keep the humidity high and slowly reduce it. Professional kilns mist the air if humidity gets to low too fast.
Cracks are likely to form when one part of the form dries significantly more than other parts.
When a dry part needs to move and a wet part can't stress builds. Too much stress creates a crack.
Even wall thickness, curves that let the wood move (sharp edges don't move well), controlled drying = almost no cracks ( it is still wood)
Al
Both provide a humidity chamber and allow some moister/water to escape the container.
If I put s rough out in a paper bag and put that bag in front of a fan the bag dries causing the moisture to leave the bag faster and the piece will likely crack.
The high humidity in the bag or box keep the short grain side of the vessel hydrated so it does not dry faster than the long grain which is supplying moisture.
The box is simple, rinse the piece with water to be sure the endgrain is wet, towel dry, one day with the flaps closed,
one day with the flaps open, one day on the self, ready to sand and finish.
Most of my HF would likely dry quite well without having the box. It may be like a security blanket. The box requires the labor of closing the flaps and opening the flaps.
A kiln has to keep the humidity high and slowly reduce it. Professional kilns mist the air if humidity gets to low too fast.
Cracks are likely to form when one part of the form dries significantly more than other parts.
When a dry part needs to move and a wet part can't stress builds. Too much stress creates a crack.
Even wall thickness, curves that let the wood move (sharp edges don't move well), controlled drying = almost no cracks ( it is still wood)
Al
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Kelly is correct. There is no difference in bound moisture and water. Silly argument really. In my kiln which I dry 150 to 200 bowl blanks at a time, depending on size. The humidity (moisture) forms on my dehumidify and comes out water. In a kiln load I have pulled as much as 31 gallons of water out. This depends on how wet the wood is to begin with.
I think it was Bill who mentioned the exploding of cell walls as case hardening, which is fairly accurate. In addition the cell walls collapse which can cause case hardening. This is why working with kiln dried wood can cut a little tougher. Air dried blanks can only dry down to its environment. The MC can only go down to what the environment will allow. Intentionally air dried wood cannot case harden because we control the air drying slowly and down to our environment. Case harden is a combination of speed in drying and drying to a low percentage of moisture which is hard to do air drying, in kilns it is easy to do if your not paying attention.
I think it was Bill who mentioned the exploding of cell walls as case hardening, which is fairly accurate. In addition the cell walls collapse which can cause case hardening. This is why working with kiln dried wood can cut a little tougher. Air dried blanks can only dry down to its environment. The MC can only go down to what the environment will allow. Intentionally air dried wood cannot case harden because we control the air drying slowly and down to our environment. Case harden is a combination of speed in drying and drying to a low percentage of moisture which is hard to do air drying, in kilns it is easy to do if your not paying attention.