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Working with green wood

Discussion in 'Tutorials and Tips' started by hockenbery, Aug 8, 2015.

  1. Russell Nugent

    Russell Nugent

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    I've had ash bowls in shavings in a paper bag split at the rim within 3 days. Although I'm pretty sure ash cracks when I look at it the wrong way.
     
  2. hockenbery

    hockenbery AAW Advisor Staff Member

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    When bowl cracks it is usually related to part of the bowl drying too quickly and not being able to warp because another part of the bowl won’t move with it.
    A few bowls <5% will crack when you do everything right.
    A bowl with a nice curve and even walls will rarely crack when dried slowly.

    Analyze the cracked bowl. Are the walls even? Are the curves nice.

    I don’t put shaving in the bag with a bowl - wet shavings increase the chance of mold and dry shavings will take water out of the bowl too fast.

    Paper bags create a humidity chamber to slow the drying. The end grain which wants to dry quicker gets moisture from the long grain.

    The bags cannot be where there is a lot of air movement or they will transport the moisture out of the bag too fast and dry the bowl too quickly.

    I also wash the bowl off in the sink and towel dry before going into the bag.
    This rehydrates the endgrain that may have dried out on the lathe and reduces rhe chances of mold.

    I swap the damp paper bags for dry ones every day for the first week to prevent mold and inspect for mold,
    If there is mold. If I see any mold I wipe the bowl with Clorox.
    After 5-7 days I leave the bowls in the bags for 4-5 months.
    Then out of the bags and on a shelf for 2 months then at about 8 months I might get a moisture meter reading below 10%. My drying room has a dehumidifier that keeps the room 50% Humidity.
     
    Last edited: May 13, 2019
    Dan Stevenson and Bill Boehme like this.
  3. Russell Nugent

    Russell Nugent

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    I'm currently experimenting to find the best way for where I am and the different woods I can get. In a bag, in a bag with shavings, seal end grain and stick in a shelf. I've definitely found the shavings cause mold.
    I'm also trying to find a good way to store them. My shop is only 12 x 20, so not a ton of space for storage, will have to come up with some creative storage spaces in there.
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I agree with AI's comment that shavings in the bag are not a good thing. They either lead to molding or behave as a desiccant and increase the chance of cracking.

    I prefer to use Anchorseal ... It is quick and easy to apply ... It works perfectly in my climate ... and my club buys it in bulk and then sells it to the members for $10 a gallon.
     
    hockenbery likes this.
  5. Dean Center

    Dean Center

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    Russell,
    Our climate is probably somewhat similar to yours. We're in the mountains and I believe you're in the prairie (?with pothole lakes), but we get some pacific weather effects and you're colder and continental in the winter, probably. Anyway...

    I wax the outside of roughed bowls, place in a closed paper grocery bag, and place on a ventilated shelf (metal or plastic with a grid rather than a solid shelf) open side of bowl in bag down. Usually 2 bowls to a bag unless small and then there might be 4-5 in the bag. This is in my basement with an ambient temp, year round, of about 65 degrees. After 5 months, I take out and place on the shelf outside the bag for a month or two, then flip upright and stack for later use.

    My good friend takes a paper leaf bag sold at hardware stores and fills it with roughed blanks, maybe 15 give or take, usually not waxed, folds the top and lets them sit on the floor of his basement until he's ready for them. Generally 6 months or so.

    If you're short on storage space in your shop, you might find an even better place for storing until dry out in the garage or a shed, or in the basement. Some place out of the artificial heat, anyway. Our living area indoor winter humidity is in the teens and would probably dry the blanks too fast.

    There are a great many ways to slowly dry the blanks and you'll figure out your own favorite method in time.
     
  6. Russell Nugent

    Russell Nugent

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    Thanks for the ideas.
    And yeah, all our lakes are just overgrown sloughs.
     
  7. Chris Short

    Chris Short

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    Wales
    The weight of the bowl, kept in a cardboard box in the house (no central heating now, and now out of the box) has levelled out. The cracks have opened 'nicely'! (I can see clear through a couple.)
    It's at about 14% moisture content. The plan's to fill the cracks with crystal clear resin. If I fill now, without the heating in the house being on, will the resin cause problems when it dries further? (I'm sure it's best to wait til it's as dry as it'll get in the winter (it might reach 10% in my house), but can't see it'll get much drier before then.)
    Thanks for any thoughts!
    _MG_8466.jpg _MG_8472.jpg
     
  8. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I would wait until the wood is as dry as it will get.
     
  9. Gerald Lawrence

    Gerald Lawrence

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    With oak and this looks like live oak the movement can be pretty severe. I have filled a crack and the fill fell out on final turn. So yes wait as long as you can for stabilization .
     
  10. Owen Lowe

    Owen Lowe

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    Yep to what Bill and Gerald, and you, said -- best to wait. I'd imagine by mid-summer you'd be good to use the epoxy. Epoxy is pretty flexible and if you fill now it will certainly turn into shallowed channels if the cracks open further. If you weigh the bowl on a scale measuring in 1/10ths of grams, it would be pretty obvious when the water loss slows down. I'd wait until the variation from week to week is minimal.
     
  11. Chris Short

    Chris Short

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    Thanks fellas, that's a great help. In future, I'll be avoiding splitty wood for green turning unless it's splits I'm looking for.
    Maybe you can help me sort this in my mind. To my understanding (just from what I've read), in winter humidity in the air is low, and the heating in the house is on - great final drying conditions. In summer, the air's warm and moist (here anyway - Wales, UK) and no heating, so wood in the house won't get as dry as it will in winter. Is that correct? (I realise in the US you have hugely varying climates so things could be very different.) If that's correct, this bowl will have to wait til winter til it's as dry as it's going to get? Happy to do that, but it's one to remember for future reference - avoid turning splitty green woods in Spring?! If I can get into green turning it'll be great - my workshop's in a tree surgeon's yard, and my hope is to get a regular turnover of bowls drying as I'm producing more (if that makes sense).
     
  12. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Cold air can't hold as much moisture as warm air. When cold air reaches as much moisture as it can hold it is saturated and the atmosphere becomes cloudy and might lead to rain.

    The term relative humidity means the percentage of moisture in the air relative to the saturation content at a stated temperature. So, 50% relative humidity on a very cold day is drier than 50% relative humidity on a very hot day. In fact, 55% relative humidity on a very cold day is drier than 45% relative humidity on a very hot day. This leads us to a term called absolute humidity measured in grams per cubic meter. On a cold winter day when you heat the air in your home the amount of moisture per cubic meter indoors is the same as it is outdoors even though the relative humidity indoors is much lower. All of this discussion is to say that absolute humidity is what determines the dryness of the wood.

    All of this information about moisture aside, your bowl is relatively thin and should be dry enough that it is stable in two or three months.
     
  13. hockenbery

    hockenbery AAW Advisor Staff Member

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    True.. if you want to get more precise. Digital thermometer/hydro meters are really cheap. Just saw a 4 pack for $12. For $3 you can know the MC of dried wood for your environment.
    The importance of drying a bowl to 8-10% MC is that most climate controlled homes target 50% for the RH
    Adding moisture in winter removing it in summer.

    The table below will tell you the moisture content of wood reaching equilibrium in a particular environment.
    C9AD0E48-39DF-49D1-9E48-9C6F099CEA21.jpeg
     
  14. Gerald Lawrence

    Gerald Lawrence

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    Another thing to remember is that "wood moves". No matter how old or how dry the climate is when you have changes in season or weather the wood will move , it is just a characteristic of the medium we use. So the advise we are all giving is get the wood as dry as your working conditions allow and live with the minor movement you will get. Do not try for "perfect dry", not gonna happen. Attaching other items a turning brings in a whole other set of conditions to deal with.
     
  15. Chris Short

    Chris Short

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    OK, got it - get it as dry as I can now, then it'll be within the usual annual fluctuation in moisture content that it's going to have to live within from year to year anyway.
    Thanks all!
    C
     
  16. Brian Longshore

    Brian Longshore

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    Great article, I found several pieces of good information. Thanks Al.
     
  17. Chris Short

    Chris Short

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    Finished the bowl today - crystal clear resin to fill the cracks, and finished with sanding sealer and wax. I'm very happy with the result, my first once-turned green bowl - many thanks for all your help! C.
    _MG_8523.jpg
     
  18. Don Wattenhofer

    Don Wattenhofer

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    I just went through your presentation document and read through many of the comments. You have covered just about everything and I like your preference for "crack prevention" versus "stabilization", because I have seen where many new turners think stable means that a dry finished turning will not expand and contract with changing humidity.
     
  19. hockenbery

    hockenbery AAW Advisor Staff Member

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    Thanks for the kind words.
    You are so right about wood moving as it dries and continuing to move with changes in humidity.

    I get asked all the time “how do you keep it from warping”
    My answer is “I plan on it warping and I can calculate the limits of the warp if I need to.”

    Fortunately a turning from a single piece of wood won’t change shape noticeably once it has dried to around 8% MC.
    In Constructed pieces changes in MC can cause joints to fail or become an unwanted texture.
     
    Last edited: Sep 14, 2019
  20. Bobby Smith

    Bobby Smith

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    Speaking of green wood, I picked up an old mesquite branch that was sitting alongside an oilfield lease road on the way to one of my rigs the other day. It had a couple cracks, but looked like it had been there a while. Thought I could maybe get a pen blank out of it. Just started cutting off the bad stuff this evening and was left with a decent size piece, maybe 1 3/4" squared and 8" long. I also noticed after squaring it up, it had some green spots on it. Put the moisture meter to it and it red lighted me at 15%. Wow, I would have thought this thing was almost dead. Lol So it will sit on a shelf for a while anyway.
     
  21. Don Wattenhofer

    Don Wattenhofer

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    Quote from Hockenbery: (Fortunately a turning from a single piece of wood won’t change shape noticeably once it has dried to around 8% MC). This is true for most turned objects if made to the standards you set forth but the thing that got me going on this came up in another thread concerning threading wood. The point made is that wood threads should be coarser then the currently sold chasing or threading jigs and have more clearance to accommodate the the movement caused by changes in MC.
     
    hockenbery likes this.
  22. Fadi Zeidan

    Fadi Zeidan

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    Wet mesquite is great for turning. Turn mesquite wet if you like, Mesquite hardly moves or warps. I love turning mesquite.
     
  23. Bobby Smith

    Bobby Smith

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    That's good to know. Thanks Fadi! I wasn't planning on turning it right now anyway. But at least now I know it won't be a problem when I decide to. I haven't done much turning lately, too busy at work. But I just started up some kitchen tools for the mom and sis for Christmas. It actually feels pretty good to get back on the lathe again!
     
  24. hockenbery

    hockenbery AAW Advisor Staff Member

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    Let’s include threaded joints under constructed.
     
  25. Don Wattenhofer

    Don Wattenhofer

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    {Wood is going to move so turn it with a shape and thickness that lets it move.
    Practice practice practice turn turn turn.
    Wood grows on trees}
    The above quote from Hockenberry sums up everything a turner needs to know for success but I would like to add to that "don't think you can dry a large piece of wood before turning.
     
    Bill Boehme likes this.
  26. Tom De Winter

    Tom De Winter

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    I’m too green to have questions at this point. (Pun not, well maybe, intended).

    I’m sure as I progress the questions will start flowing.
     
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