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Rough turned bowls cracking

Discussion in 'Woodturning Discussion Forum' started by John Hicks, Jun 17, 2020.

  1. John Hicks

    John Hicks

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    I have recently turned a few cherry, and big leaf maple large bowls. I rough turned them leaving them over an inch thick (they are green) I coated the entire bowl with 2 coats of anchor seal. They are cracking at about three weeks. What a waste! I keep my shop at 55% humidity with a dehumidifier. I live in the Olympics area, so there is no lack of humidity. Each bowl has two or three cracks in different places. Not to mention the cherry went so oblong after three weeks, I don't think it would be possible to re mount it anyway. I have an entire big leaf maple tree, and some very large logs that are cherry; I don't want to ruin all that wood! What is a good way to dry these out without them cracking?
    IMG_6811.JPG IMG_7189.JPG IMG_7191.JPG IMG_7192.JPG
     
  2. Damon McLaughlin

    Damon McLaughlin

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    John,

    If I'm rough turning bowls I turn the rim to a thickness of 10% of the overall diameter. For example if I'm turning a 12" bowl I'll leave the rim about an inch and a quarter. I only seal the end grain on the outside of the bowl. I don't seal the inside. When stacking I sticker the bowls to allow for air flow. Sometimes the bowls will be placed in a paper bag (sometimes with shavings) for up to a week or two first. If the wood was wet enough where water was spinning out of it or can be seen on the surface I place it in a paper bag for a week or before sealing it with anchor seal. I have noticed that blanks with knots are more prone to checking, especially around the knot. I still get some checked bowl blanks but not many.

    Have you thought about finish turning green bowls and letting the warp be part of the character?

    Damon
     
  3. Richard Coers

    Richard Coers

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    How are you storing the rough outs? You want very little air movement around them, and 55% humidity is not kind to wet bowl blanks. Knots don't help one little bit either. I store all rough outs in a yard waste bag. It is double thickness. After 2 days I move the blanks into a dry bag and hang the wet bag on the clothes line. I just keep rotating for a few weeks if its fruitwood. Then I will bring it out of the bags and let it rest. After a couple more weeks, it goes into a upright freezer converted into a kiln. There temps start at 90 degrees. Plenty of references on the AAW site written by John Jordan and David Ellsworth on drying and methods to reduce cracking.
     
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  4. Don Wattenhofer

    Don Wattenhofer

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    Cherry is one of the most apt to crack.
    Something to try would be a shallower bowl where the rim is not at the half circle point but maybe at something like a 1/4 circle. The end grain fibers on your bowl are no longer than the wall thickness where as the fibers on the lower part of the bowl will be much longer than the wall thickness.
    20027BowlT.jpg
     
  5. hockenbery

    hockenbery AAW Advisor Staff Member

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    All the advice above is good.

    Avoid Putting drying bags in front of a forced air vent or under a fan since this will cause the bags too wick moisture and the bowl to crack from loosing moisture too quickly. The ispdea of the bags is to make a humidity chamber that keeps the endgrain damp so the long grain can loose moisture at a similar rate..

    when you rough. Go for a smooth surface with less tear out.
    The smooth surface will dry more uniformly and the returning The dried bowl will be so much easier when starting with a smooth out of round surface.

    as above make the rim 10% of the diameter. Turn the walls a little thinner working into the bottom that is 10% of diameter less almost 1/2” for the tenon. If the rim is an 1.5” then gradually make the wall thinner until the Ex bottom is 1 to 1 1/8” or so going into the tenon.

    often there is wide spot in the wall of the bowls that causes crack.

    main thing is greatly slow the initial drying keep the bowls wher circulation of air is minimal.
     
  6. hockenbery

    hockenbery AAW Advisor Staff Member

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    This is easy to check with a ruler.
    Some of it is optical illusion.
    Also the endgrain rim bumps get cut down to the side grain rim heights.

    worst case is a shallower bowl than planned

    If you look at the dried bowl I remount In the demo video in the returning a dried bowl thread. It is super oval but I line it up to get the thickest wall.
    https://www.aawforum.org/community/index.php?threads/re-turning-a-dry-bowl.12610/
     
  7. Lars Hansen

    Lars Hansen

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    O.T., but: John, I absolutely *love* your avatar! A young lady close to me owns a bulldog and that expression of disapproval is SO familiar :D
     
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  8. odie

    odie

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    ^^^^^ I agree.....love that bulldog! ^^^^^

    You might want to consider forgoing the bags and shavings, and anchorseal immediately after roughing. Also, the 1/10th rule is only a suggestion......you could go thicker. Both these things will necessarily increase the seasoning time, but if you've got lots of roughouts in progress, that isn't a big consideration. Time is your friend, when seasoning roughout bowls......:D

    @John Hicks ......Out of curiosity, did you check the MC%, when you roughed?

    -----odie-----
     
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  9. Roger Wiegand

    Roger Wiegand

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    A lot of times the cracks are there before you start. I recently collected a lot of really big maple blanks from a tree a neighbor took down that turned out to be afflicted with radial shakes (sometimes called frost shakes). These are pre-existing hairline cracks in the wood that run around the growth rings that may be the result of wind damage or freezing. The wood, while beautiful , is pretty much firewood. Unless you looked closely you wouldn't notice them, but they open up big time as the wood dries.

    Checks that come in from drying at the ends are a major culprit, you need to cut off well beyond the visible check to get back to solid wood. If you have even the finest hairline crack it will open up, there's no way to hold it together once the crack has started. My drying success rate has gone up a lot since I've started being ruthless about eliminating anything that might already have a crack started.

    Depending on the wood you will almost invariably get cracks around knots.
     
  10. John Hicks

    John Hicks

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    Yes, it's around 33%. I put two coats of anchorseal on the entire piece(s) It's probably drying out too fast in my shop with the dehumidifier running?
     
  11. john lucas

    john lucas AAW Forum Expert

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    roger nailed it. When I'm cutting blanks out of a log I cut off 3/4" break it. If it breaks it has cracks. When It won't break I cut the bowl blank and then wrap it in plastic immediately. I've had cherry start cracking before I get it home from cutting it on someones farm. We are talking just a 20 minute drive plus a little time to unload it before trying to seal the ends. I also don't leave any sharp edges on my rough turned bowls. I leave the bottom with the foot the same thickness as the sides. The bottom won't warp as much so you don't have to remove much material so you can get away with that. I also store all rough turned bowls in a room with little air movement and no direct sun.
     
  12. Kent Jaffrey

    Kent Jaffrey

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    Sometimes the cracks are already there and you just don’t know it, especially if the tree had been down a while. Also I was wondering how hick a coat of anchor seal you applied? I usually use one coat on he end of just cut blanks but that one coat usually looks more waxy than your two coats on that bowl. So make sure you aren’t being too stingy with the sealer.
     
  13. Emiliano Achaval

    Emiliano Achaval Administrator Staff Member

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    That's nothing, I welcome small cracks like that so I can apply pewa patches and charge more for the bowl. When I read your post I assumed I was going to see a bowl split in half or something along those lines.
     
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  14. Dean

    Dean

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    John, I live in an area that runs 25-50% humidity. In the summer it is hot and if I’m making blanks. I have to be very careful with the loss of moisture once I open the log up. When I cut the blanks with the chainsaw I stack them up and keep a water hose handy and keep them as wet as I can. I keep a tarp over them. And wet them after every couple blanks. Then I bandsaw them round and stack them up on a little furniture dolly and put a trash bag down over them. I then cut the outside profile and recover with a bag until I core them as I core them I keep them in wet shavings until I clean them off and seal them, then I stack them up with stickers on the dolly and push them into the back corner of the shop after 6-7 months I will check them for moisture but typically it is 9 months or so before I get the dry ones turned.
    The point to this long post is maintain the moisture as long as you can until sealed. If it ovaled in 3 weeks it is loosing moisture too fast. Coat the entire bowl with sealer. I cant be sure but your may have lost too much prior to sealing. Unfortunately cherry is akin to oak and they both love to lose moisture fast These two wood are always challenging.
    I hope I was of some help to you sir.
     
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  15. John Torchick

    John Torchick

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    Dean's reply was interesting. I recall driving by a sawmill in Florida. The sawmill had a sprinkler system that sprayed a light shower over the logs. Always wondered why...now Dean has answered the question.
     
  16. Mike Johnson

    Mike Johnson

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    As John Lucas mentioned above, any sharp defined edge on a rough turned bowl blank will increase the potential for a crack to start. You are better off rounding the rough turned "rim" of the bowl over with a smooth transition. A sharp edge dries out too quickly.
     
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  17. John Hicks

    John Hicks

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    I'm learning. Lot's of good advice here. I guess I need some help slabbing as I'm very slow with a these wonderful disabilities. I'm going to make a sawbuck that I can roll logs onto and get a better position for slabbing. I have almost a whole cherry tree with some of the pieces weighing well over 200 lbs. So far, after keeping them in the yard on pallets, with a tarp over them, none have started checking yet; but I am NOT looking forward to handling them!
     
  18. robo hippy

    robo hippy

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    Well, generally if you are drying it too fast, it will crack. If you are drying too slow, it can mold. Add to that the different personalities of the woods, some times you just can't stop it. One thing here stood out to me, and that is the crack appears to be coming off of a 'defect' in the wood. Any knot or defect will generally crack, and it is not if, but when. Cherry is also prone to cracking. I keep mine on the concrete floor for a few days, then up on wire racks to finish drying. I do turn green to final thickness and let them warp. I would think the 55% humidity would be a bit low, and in the Pacific NW, the natural climate is pretty good for air drying wood.

    robo hippy
     
  19. odie

    odie

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    John.......

    33% MC is pretty wet, and you're going to lose half of the total moisture you're going to lose in the first 30 days of seasoning. The rest of the moisture loss will be incrementally less with each month of seasoning......until you reach stabilization, in which the MC will vary only very slightly, depending on your climatic conditions. The total time for the seasoning process will vary between wood species, and individual specimens/conditions.....and the time could be only a few months, to over a year. I've found the only way to know for sure when stabilization has occurred, it to monitor the weight monthly, until it stabilizes (within a few tenths of an ounce +/-) for a 3-4 month period.

    The humidifier?.......I'm not sure about that. It might contribute to the conditions in your shop, and effect the rate of moisture release.....maybe someone else can comment about that who has experience with how humidifiers effect the moisture loss in seasoning bowls.

    Robo mentions mold/mildew, and I've found it to be problematic for a MC of around 18-20%. It doesn't seem to be a problem above or below that range of MC. It's usually only on the surface, and a quick return to the lathe and take off a layer of surface wood usually solves the issue.......as long as the MC has progressed to below the 18-20% range......if not, it could return within the next month.

    Others mentioned that cracks could be present prior to roughing and seasoning bowls......and, this could be so. If so, there really isn't anything that can be done to prevent them from opening up during the seasoning process.

    You mention that you've applied two coats of anchorseal.......and, I'm assuming your intent is to further slow down the moisture loss during seasoning.......correct? I've never used more than one coat of anchorseal, unless I've missed a spot, and come back with a second coat later on. I can't say for sure that a second coat of anchorseal will significantly retard the moisture loss.......it's pretty thin stuff. My thought is if you want to significantly retard the moisture loss, then a heavier wax coating might be the way to go.......open to other thoughts/comments on this.

    -----odie-----
     
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  20. Karl Loeblein

    Karl Loeblein

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    If the wood is really nice and you have the time then consider returning the bowl blank several times during the drying cycle. Reseal between turnings. Make sure to remove any cracks each time or else they will only get worse.
     
  21. Gerald Lawrence

    Gerald Lawrence

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    I could not add any to the other excellent posts on the problem but, I see this idea that it takes as much as a year to stabilize the moisture content in a turned blank and have to wonder where do y'all live , under the ocean? Yes the weights work great but for my shop usually within to months is only losing 5 to 10 GM in 5 days. It is not necessary for the MC to stabilize to no further change. The little moisture left at that time is inconsequential unless it is for a box.
     
  22. John Hicks

    John Hicks

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    I guess the next thing I'll do is look for a giant freezer to turn into a kiln. Lot's of free broken freezers around here.
     
  23. robo hippy

    robo hippy

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    While I have never even considered a freezer type kiln for drying, I have often wondered why people don't just make a plywood box with wire rack shelves and put the light bulb under it. Convection, as in hot air rises, will move plenty of air as long as the box is open on the top and on the bottom.

    robo hippy
     
  24. Donovan Bailey

    Donovan Bailey

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    I know that I'm going to make a statement that is borderline wacky even to me,..but I can tell a significant difference in the workability (is this a word?) of air dried vs kiln dried wood. It is my opinion that air dried wood cuts, sands, and finishes much easier and better than kiln dried wood. Yes...go ahead and laugh...but there it is.
     
  25. hockenbery

    hockenbery AAW Advisor Staff Member

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    I have heard that a lot from flat wood people.
    I know for sure the turning wet wood is a lot more enjoyable for me than turning air dried or kiln dried wood.
     
  26. Don Wattenhofer

    Don Wattenhofer

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    Nuttin to laugh about! Back in the 1970's I made two pair of snowshoes that were made of ash for the frames. The ash I used was kiln dried lumber that I shaped the side rails out of then boiled them and put them on a form to set the shape. In the process of bending the wood there were several splits and some partial cross grain breaks, the splits I glued back in place, and I was able to complete the 2 pair. The family grew so I needed 2 more pairs so that time I did a little more investigating the science of wood bending and found that kiln dried is brittle, where as green wood is more pliable. I found a small straight black ash and using a froe I split it in half, then quarters, then eights. The rails made from the non kiln dried ash bent and held the curves better and were not as brittle.
    So you have just rediscovered the truth.
     
  27. Jason Matisheck

    Jason Matisheck

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    I'm having a similar learning curve with drying blanks. My plan was after they dried to fill the cracks with colored epoxy and call them a feature. Or, turn my bowls into plates.
     
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  28. John Hicks

    John Hicks

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    I discovered that if you get it for free, it will crack.
     
  29. Don Wattenhofer

    Don Wattenhofer

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    Rule #1 do not dry blanks period. Rough turn blanks while still green then dry. Review this entire thread and numerous previous threads for insights into successfully drying bowls also study the characteristics of wood as it dries to understand why wood cracks.
     
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  30. odie

    odie

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    Heh,heh,heh........Well, Gerald......obviously your experience is entirely different than mine. From my perspective, if it continues to lose weight on a month by month basis, it isn't stabilized yet.....end of story! :D

    edit: Any moisture that can eliminate during the seasoning process, is best. This is because it WILL eliminate after finish turning. If it eliminates during, or after the finish turning process, then it will contribute to conditions that cause warping + cracking. :(

    -----odie-----
     
    Last edited: Jun 22, 2020
  31. hockenbery

    hockenbery AAW Advisor Staff Member

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    I get that you are joking - :) That argument is sort of like the rooster causing the Dawn because he crowed before sun rise every day. :)

    What Is true is that new turners get lots of cracked bowls experienced turners get very few if any cracked bowls.
    Don’t be discouraged.
    good news - once you get a good class or lots of self taught experience you get to be an experienced turner.

    Experienced turners:
    start with crack free wood
    keep the wood from cracking before they prep the blanks.
    go from blank prep to finished rough out in less 30 minutes - wood doesn’t dry out on the lathe
    turn flowing curves
    turn even wall thickness
    Control the drying of the rough out.
     
  32. robo hippy

    robo hippy

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    There is a big difference in how 'kill' dried wood works and how air, vacuum kiln dried wood, and solar kiln dried wood work. If you rip a kiln dried board on your table saw, you get saw dust. If you run one of the other boards through with the same cut, you get shavings, not dust. I have also noticed that when ripping 8/4 boards on my bandsaw for bookmatching, I don't get any cupping or warping of the boards. I do know the solar kiln takes more time than the vacuum kiln. No clue as to what actually makes the differences. Not sure if bowl blanks could be done in a vacuum kiln or not.

    robo hippy
     
  33. Roger Wiegand

    Roger Wiegand

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    I've discovered that all too often if you've paid big money for it it will crack. Much more painful. :rolleyes:

    Here's a prime example of what not to do. I started working on this piece of hackberry, DW called with something she needed help on. That turned into a more prolonged distraction. 15 hours later on the lathe my piece looked like this:

    [​IMG]
    So this is an example of doing everything wrong. The wood was too dry to start with and probably had incipient cracks and the walls were left way too thick on a relatively warm, dry day, with nothing to prevent evaporation. The upside was that I suspect I could have put in a lot more work before those cracks opened up, as it was I was just starting. It was a piece of wood I was trying to save because it came from the local arboretum and they like to get pieces made from their wood back for a turning show they do each fall.
     
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  34. odie

    odie

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    I can remember that happening, and the lesson I learned is to finish the roughing process turning in one session, including the anchorseal application, which is always immediately applied after roughing. For me, it wasn't my significant other calling me away for something else, but I was tired, and thought I could finish the roughing in the morning.......nope, doesn't work that way! :D

    Al feels it's necessary to finish roughing in 30 minutes, and while I'd have to agree that roughing without delay is best, many of my roughed bowls take me up to a couple hours +/- to complete the process, and I've not had much problems with taking a little extra time with it. This is because I do a lot of contemplating the wood characteristics to determine the best way to take advantage of what's available, and what I wish to eliminate. I recently spent $175 for a large red mallee burl bowl blank that had flaws, and warping. (I don't have the information about that bowl blank in front of me, at the moment, but I think it was initially around 25% MC.) Anyway, it took at least a couple hours to rough that one, and it's now anchorsealed, and in the seasoning process.......no noted problems with it, but I expect it to take the better part of this year to season properly......maybe next year before it's ready to finish turn......;)

    -----odie-----
     
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  35. Gerald Lawrence

    Gerald Lawrence

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    Wood cracks and is we are lucky we beat it to the point by making something of it first. To remove the stress from all this remember "It grows on trees".o_O
     
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  36. hockenbery

    hockenbery AAW Advisor Staff Member

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    If you get an opportunity to see really good bowl turners work -
    Glenn Lucas, Mike Mahoney, Trent Bosch, Al Stirt, David Ellsworth, Dale Larsen, and dozens of others....
    Note how long it takes them to do a bowl in demo then realize they are spending 80% of the demo not turning.

    speed is not super important but it does reduce cracking.

    what is important is the second part of that line
    I spray water on turnings using a plant mister if they will be on the lathe for a while most hollow forms over 10” d get misted multiple times while hollowing. If I have to interrupt turning I mist the piece and wrap it with plastic since a minute away can often become a couple of hours.
     
    Last edited: Jun 22, 2020
  37. Don Wattenhofer

    Don Wattenhofer

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    In relation to all of the comments about speed to prevent checking I have a simple answer!
    When ever I start roughing a piece and the clock or my stomach or what ever causes me to stop I always try to wrap the turning with a plastic bag and so far have not had any problems (or checks). The bag should not be left in place for more than a day or you may get mold and or badly rusted chuck jaws.
     
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  38. Donovan Bailey

    Donovan Bailey

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    .[/QUOTE]
    This same process has never failed me.
     
  39. Glenn C Roberts

    Glenn C Roberts

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    Roger, why the hole in the tenon?
     
  40. Roger Wiegand

    Roger Wiegand

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    Tenon is on the other end, it was intended to be a hollow form and that's the top. I drill a hole with about the final opening I want and as deep as I want the vessel to be. Usually I finish the outside pretty quickly and am on to hollowing it before problems develop.
     

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