I'm working on a small -- 6" diameter -- cherry bowl. Moisture meter says this blank, rescued from a hunk of firewood, is 22%. I'm about done roughing it and will coat it with anchorseal. At what moisture percentage can I finish the turning? About how long should I expect it to take to get to that point?
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Drying to what moisture percent
- Thread starter Lawrence Tarnoff
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Your weather conditions might be different than mine.
For me, a 6" black cherry roughout would have a wall thickness of about 5/8" and get put into a paper bag and set on the basement floor in the summertime, or put in an unheated outbuilding or garage in winter. After two or three weeks, the bowl would be taken from the bag and allowed to finish drying. Cherry dries fairly fast, and for a 6" bowl, it might take another 3 weeks to two months. If checking with a moiture meter, 12% or less would be 'good to go' for me. In your area, the percent may be different. Check with the meter weekly, and when is stabilizes for a couple of weeks, it is ready. Larger heavier wall bowls take longer. Woods other than cherry take longer.
I would not put anchorseal on a bowl that small, and usually only put anchorseal on the end grain quadrants of wood that is prone to crack. Anchorseal will interfere with a moisture meter's ability to read correctly.
The shape of a bowl has a lot to do with cracking. A largish flat bottom with relatively straight up and down sides is difficult to dry without cracking, regardless of how slow the drying process is. Uneven wall thickness also increases the likelyhood of cracking.
For me, a 6" black cherry roughout would have a wall thickness of about 5/8" and get put into a paper bag and set on the basement floor in the summertime, or put in an unheated outbuilding or garage in winter. After two or three weeks, the bowl would be taken from the bag and allowed to finish drying. Cherry dries fairly fast, and for a 6" bowl, it might take another 3 weeks to two months. If checking with a moiture meter, 12% or less would be 'good to go' for me. In your area, the percent may be different. Check with the meter weekly, and when is stabilizes for a couple of weeks, it is ready. Larger heavier wall bowls take longer. Woods other than cherry take longer.
I would not put anchorseal on a bowl that small, and usually only put anchorseal on the end grain quadrants of wood that is prone to crack. Anchorseal will interfere with a moisture meter's ability to read correctly.
The shape of a bowl has a lot to do with cracking. A largish flat bottom with relatively straight up and down sides is difficult to dry without cracking, regardless of how slow the drying process is. Uneven wall thickness also increases the likelyhood of cracking.
22% is dry enough to burn in the fire place. You could, if you wanted, turn it to final thickness, sand, and finish it without waiting for it to totally dry. Outside drying will get to 12% or slightly more or less depending if you are in thunderstorm country, or Death Valley. If you are going to let it sit for a while, I would at least put some stretch film around the outside rim, and make sure to round over the bowl rims.
robo hippy
robo hippy
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Depending on your desired outcome, you could finish turn it now. It'll move a bit, but sometimes that's what you want. Important thing to consider is that moisture loss/contraction are pretty linear. You're about half done in your trip from a fiber saturation point of 30% to a good average of 10% in most locations in an inhabited dwelling.
How long depends on how much sealant you apply, and where it is. Outside endgrain is the money place. More territory you cover, more you slow things down. Since the interior is under compression as the wood shrinks, you can disregard it altogether.
You can test or weigh as often as your impatience desires, or you can take a basic truth of wood - shrink equates to loss - and apply that to your piece. What it weighs or what your meter says is immaterial, until the wood's contracted to a fairly definite degree. For me, the key is the differential diameter of the mortise on the bottom. I use 2", and when there's ~ 1/8 difference between along and across, I'll weigh. Cherry at an inch is a two/three month item when left bare. Less than an inch doesn't decrease geometrically, but half thickness dries maybe three times as rapidly.
How long depends on how much sealant you apply, and where it is. Outside endgrain is the money place. More territory you cover, more you slow things down. Since the interior is under compression as the wood shrinks, you can disregard it altogether.
You can test or weigh as often as your impatience desires, or you can take a basic truth of wood - shrink equates to loss - and apply that to your piece. What it weighs or what your meter says is immaterial, until the wood's contracted to a fairly definite degree. For me, the key is the differential diameter of the mortise on the bottom. I use 2", and when there's ~ 1/8 difference between along and across, I'll weigh. Cherry at an inch is a two/three month item when left bare. Less than an inch doesn't decrease geometrically, but half thickness dries maybe three times as rapidly.
odie
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Lawrence.........
There are various methods turners use to conclude a Cherry bowl will be dry, and ready to finish turn. Some finish turn at a higher MC (moisture content) than I do. Those who do tend to use the higher MC, and degree of warp they'll get advantageously in pursuit of their own turning style. This is fine, but it's my objective to stabilize the MC to the ambient atmosphere at my location. I do this, because I would rather deal with the least warp possible within the confines of natural seasoning methods. In doing so, the lesser degree of warp is helpful towards my style of turning. Finish cuts are more controllable, and sanding a bowl that is as perfectly round as possible is better for the fine finishes I get.
I initially started out measuring MC with a moisture meter exclusively, as you are doing......and, finish turn when it's below, or around fourteen percent. This method didn't work out for me as well as I'd like, so I now use the moisture meter for getting a "ball park" idea of how the seasoning process, and time involved will pan out. After the initial moisture content reading, the bowl is roughed and completely anchorsealed. I seldom anchorseal any less than the entire roughed bowl......the exceptions to this would be bowls that are initially under around fourteen to sixteen percent to start with. There, I may choose to anchorseal only the endgrain......or, not at all.......it all depends on the wood species, and grain configuration. Denser woods usually have total anchorseal, even though they meter an initially low moisture content. I'm a little more lax with wood that is already low in MC, and the species tends to dry with minimal problems......but, nothing is chiseled in stone! ......use judgement.
Now, my method is to log monthly weighings, and when I get three consecutive months of no loss of weight, I call it good and consider the roughed bowl to be ready for finish turning. I don't always use the moisture meter at this point, but when I do, the roughed bowl is seldom more than twelve percent MC. It's not the percent of moisture content that's important here......it's that the roughed bowl has stabilized to the environment I have at my location.
If a bowl does not warp to some extent with the final turning, it's an exception to the rule. My objective is to keep the warping to the absolute minimum, and stabilizing the MC to the ambient atmosphere is a better indicator of that, than is an arbitrary number from a moisture meter that will supposedly cover all species, sizes, shapes, and initial moisture content.
Along with my Mini Ligno E for determining initial MC, I use a postal scale for monthly weighings.......and these scales are very common, easy to get, and are plenty cheap! Many of us have both the scale and a moisture meter........and, that's what I'd suggest. Either one will get you from A to B......but, you have the best overall predictor of what any individual roughed bowl will require, and confirmation of stabilization, if you have both.......
ooc
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