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Microwave Bowl Drying?

Discussion in 'Woodturning Discussion Forum' started by Jon Minerich, May 18, 2012.

  1. Jon Minerich

    Jon Minerich

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    I bumped into a fellow who has been wood turning for several years. I told him that I acquired a bunch of green cherry and sycamore limbs from a neighbor. He mentioned that he dries his small pieces of green wood in a microwave with excellent results.

    Have any of you folks done this? Can you give me some advice on how to proceed? Are there any articles out there?

    Thanks!
     
  2. Rob Wallace

    Rob Wallace

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  3. egsiegel

    egsiegel

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    my only advice is to do it when you wife is not around...
    don't ask how I know :rolleyes:
     
  4. john lucas

    john lucas AAW Forum Expert

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    I don't do it often anymore but I spent some serious time playing with microwaving about 5 years ago. 2 things. One is to stay with the machine. I had cooked a bunch of bowls and boxes and got cocky about it and left one while I did something else. A sap pocket of something inside the wood heated up enough to burn a hole in the vessel, smoke up the enterior and it took a month to get the smell out. Thank god I was single at the time. I now have a microwave in the shop.
    The second thing for me was I used many short cycles and didn't rush it. I would use between 30 seconds and a minute and then let it cool a lot between cycles. What I usually do is heat it, pull it out and then go do something else. When I thought about it I'd heat it again. Sometimes during lunch or a phone call I might go through 3 to 5 cycles. I plan on more or less all day and just don't get in a rush. It went smoother with fewer failures when I took my time. I just weigh the wood often and stop when it's dry.
    At that point the wood is actually too dry. Let it sit for a day or so if your making boxes because it needs to pick up some moisture and stabilize. For bowls of course it doesn't matter.
     
  5. Dale Bright

    Dale Bright

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    When I use the micrwave, I wrap the wood in a paper towel and place it into a plastic grocery bag. I use the high setting for 20 seconds. Take the piece out, unwrap it and let it cool. Let the paper towel dry or use a fresh one. I do this several times until the paper towel is dry when I unwrap. The dry towel indicates a dry piece of wood.
     
  6. MichaelMouse

    MichaelMouse

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    Dries from within. Really good idea, but demands caution, as you can see by the replies.

    1) Don't cook stinky woods. Willow, elm and so forth.
    2) Don't supply energy continuously, or those dense, drier spots insulated inside the damper wood will ignite.
    2a) Use "low power" settings. These supply energy in short spurts, with time between for water to migrate a bit. The machine will do this for you on low settings and longer times.
    2b) Spend your own time to zap short, cool as John does.
    3) Protect your microwave from excessive moisture.
    3a) If you follow 2b, take the piece out to offgas. Electricity and moisture are not a good pair. That's why the fan runs when the oven is operating.
    3b) Bag your work. Plastic is good, because vapor builds to saturation and then condenses after you take it out. Good buffering. You can zap, condense, turn the bag inside out, zap again. When there's only a bit of a cloud instead of drops, you're rare enough to spend a few hours equalizing the surface and going back to work.

    If you're going to form the piece while plastic, wear good gloves! You can take a fairly thin steamed piece, squeeze to circular, or to more exotic shape, and hold. Can be fun.

    One big drawback is that you can end up with spotting on the wood. For plumbing reasons, the water will find the path of least resistance over and over again, and carry the darker extractives along with.
     
  7. Patrick Miller

    Patrick Miller

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    Microwave bowls

    What I have done is coat the rough turned bowl with sealer, at least on the end grain, put it in a paper bag and hit it hard to begin with, 5 minutes at full power. I get the piece out of the oven (and wipe the moisture from the inside the oven) and let it cool and hit it again. 5 minutes full power and maybe again. I check the weight and moisture content before I start and each time it comes out. As the piece gets down in weight by 30% or so I go with decreasing power and time. If I get cracks I fill them with CA. Hot CA is really nasty on the nose and eyes. and "Yes" you can set a bowl on fire this way- DAMHIK- I let the blank set in the shop for a day or two to stabilize. Looks like my technique may be a bit more of a 'bull in a china shop' approach but my mentor taught me the method and I've had pretty good luck with it. I bought my wife a new MW for the house and took the old one to the shop. A most harmonious $100 expenditure......
     
  8. Barry Elder

    Barry Elder

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    Drying wood in a microwave oven works very well. Google is your friend. There have been articles available for years. But I have found that it is not something that you can set and then ignore while you go off to do something else.
     
  9. odie

    odie

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    The trouble with microwaving, or any other alternative way of drying bowls, other than the good old fashioned way of doing it, is that very few of these methods have as good a success rate. About the best one could hope for is to dry bowls as good as "Father Time".

    The reason for this is really very simple......remove moisture, and whatever is left is subject to internal stress that causes the wood to move......or, warp. The quicker the MC is removed, the greater the effect it will have on the wood itself. Really.....it's all about Father Time. He is your friend, because the wood is allowed to warp with varying degrees of MC during the process. This is why the wood can warp with a higher success rate. It only makes logical sense that if you remove all the moisture quickly, the wood will warp quickly.......and, this is what causes drying cracks. The goal is to let the wood warp gradually.

    All of these alternative methods of drying the wood, is symptomatic of one thing.......most woodturners just don't want to wait for nature and time to do the job......it's a lack of patience.

    Matter of fact, many turners realize Father Time is such a good partner in this endeavour, that we fully coat the entire surface of a roughed bowl for one specific purpose.........to slow down the process even further!

    Using time as a component of the strategy will not mean the success rate will be 100 percent......get over it, and accept it. You're going to lose one here and there, but if you're doing things correctly, your success rate will be in the high 90s percentile. Wood is what it is.......an organic material that lives in a world that YOU have to adapt to......not the other way around!

    ooc
     
    Last edited: May 20, 2012
  10. Dick Sowa

    Dick Sowa

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    I have had very good results with microwave drying, but learned some lessons the hard way.

    -If you leave partially dried wood in the microwave overnight, you might wind up with black mold growing. I was doing some maple, and got an ugly piece the next day. Take it out and leave it in the open air if you need more days of zapping.

    -Get rid of the pith and more. There's nothing more disappointing than seeing cracks develop in a matter of minutes.

    -To be really effective, you should rough turn the blank before microwaving, and be really, really patient. Microwaving does dry a rough turned bowl in a day or so, but it also takes all of that day. You need to stick with it.

    Finally, I agree with Odie...unless I have a really good reason for microwave drying, I opt for letting nature take it's course.
     
  11. Jon Minerich

    Jon Minerich

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    Thanks for all the advice-both pro and con.

    I guess I must learn more patience. I remember my Mom saying something like that a long, long time ago. Ya, I am a slow learner. . . :)
     
  12. John Torchick

    John Torchick

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    I haven't MW'd wood- yet, but I have heard of other rodbuilders that MW slowly. Sort of like defrosting in the MW rather than going full power all at once. Got to try it on some bartlett pear wood I see along the road, already cut into short lengths.
     
  13. Rob Wallace

    Rob Wallace

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    John,

    I think you might mean Bradford Pear (an ornamental pear) - if so, I can tell you that it dries well under normal (i.e. non-microwave) conditions with minimal cracking and minimal distortion It turns beautifully! (I'm not so sure about its resiliency properties if you intend on building fishing rods with it.)

    Rob
     
  14. John Torchick

    John Torchick

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    Rob, it is bartlett pear- I posted today about turning it. It is a small decorative tree. Pretty blossoms in the spring but, WOW! do they stink! I'm not building rods but using it for reel seat inserts.
     
  15. Thomas Stegall

    Thomas Stegall

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    Generally the faster something dries the greater your ability to bend it to a final shape. So for thin walled items using the microwave can produce some interesting shapes either by letting it move its own way, or by applying force to bend it. Johannes Michelson discovered this and went from slow drying his hats while bending them and now dryes them more quickly when he wants to bend them significantly.
     
  16. John Torchick

    John Torchick

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    Went back and re-read the thread. First, it is bradford pear. My mistake and so early in the month!
    Odie, some of us are at the age that we don't even buy green bananas!:p
     
  17. odie

    odie

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    Howdy John.......

    At 63, I'm probably up there with some of the elder turners!......:D

    I do understand your point, though. It's a very seductive concept to have seasoned roughed bowls almost instantly. Sure, I consider the old established method of drying bowls with the "Father Time" approach, as the best overall......but, it can't be denied there are those who are using the microwave (along with a few other methods) with success.

    I don't know how many bowls others are finishing on a regular basis, but my average is somewhere in the neighborhood of one per week.......that number has remained a constant for the last decade, or so. I'll be retiring soon, and it's my intention to step up production somewhat, when that happens.........maybe, double that.

    There is a way to use time to best advantage while maintaining a constant supply of bowls ready to turn. It's really no secret among many turners, but "quantity" is the answer. At this time, I have somewhere around 100 bowls roughed and anchorsealed, and are being weighed monthly. There have been months where no roughed bowls are ready to finish turn.......and, to the best of my recollection, there have been months where more than twenty bowls have shown to have stabilized, and are added to the available finish-able stock on hand. Overall, it evens out, and at the rate of production I shoot for, I don't recall ever being "empty handed" for something to throw on the lathe for final turning........

    There are other bowl blocks that are kiln dried, or have been pre-seasoned by those who sell them commercially. If the MC is less than around 12 percent (not a hard number), they are good to make a finished bowl in a single session. Above that number, and there will still be some seasoning necessary, but it will be abbreviated. The down side to this, is nearly all of this stock is 2", or less in thickness. I have seen some kiln dried wood that was 3" thick, but this is a very rare commodity.

    Of course, ALL of this is my opinion, only........those who choose other methods of drying..........go for it! :cool2:

    ooc

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  18. John Torchick

    John Torchick

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    Odie, many of us who are retired find we have less time than when we were working full time. I have a close friend who retired 2-1/2 years ago. He said he didn't know how he found time to work!
    I enjoy looking at the bowls you turn and your willingness to share your knowledge. Thanks.
     
  19. odie

    odie

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    You are certainly welcome, John........

    I've been working on the theory that by attempting a thorough explanation of my ways of turning, my own knowledge becomes stronger. I think there is some truth to this, plus my input always seems to inspire others to give their own points of view. Both things have served purpose, and has been helpful to me. As a result, I see my own strong points, plus others have given me basis for modification of my own thinking and techniques..........I believe this is a very good thing, because contemplation and comparison testing leads me in an evolution to become a better turner overall.

    I've heard from others about not having enough time after retirement. Staying busy and engaged is an important thing, I believe......so, I certainly hope there isn't enough hours in the day to turn.......! :D

    ooc
     

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