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Thread: Bowl wall thickness

  1. #1
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    Bowl wall thickness

    Iíve been learning to turn bowls recently and have a dozen green-turned and now dry bowls ready for final shaping. Iíve noticed (perhaps incorrectly) an emphasis on even wall thickness. Understand that for drying but is there any reason the wall should be uniform thickness in a finished bowl? I.e. a tapered wall, thick at the base and say half as thick at the rim. Or a vase with a uniform cylinder inside but varying thicknesses of the walls due to esthetic shaping. And can the base be any thickness without any relationship to the walls? Iím not addressing esthetics or appearance but wondering what the wood does over time.

  2. #2
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    Bernie -- You can do anything you want. Uniform wall thickness is desirable only because otherwise the turned object's weight may feel 'off' in your hands. Humans are very good at how much an object will weigh before we pick it up. If a bowl's walls are thin on top and thick on the bottom, the bowl will feel heavy. (Sometimes that's desirable. More often, it's not.
    David Walser
    Mesa, Arizona

  3. #3
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    I find the bottom thickness to be a more important feature than you might think. Your eye (well mine anyway) picks up on the height of the bottom of the bowl relative to the surface it's sitting on. If the bottom of the bowl seems perched too high, relative to the perceived thickness of the walls, it seems discordant and distracting to me. I'm sensitive to this because fear of making a funnel causes me to often err on the thick side when approaching the bottom of a bowl, and I invariably regret it.

    There are some aspects of proportionality the have deep roots in the human brain (e.g. golden proportions), but by and large, beauty is free for you to define. I see some bowls that others like very much that I don't care for, and I'm sure there are many that view my work the same way. Do what pleases you.

    Best,

    Dave

  4. #4
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    Quote Originally Posted by David Walser View Post
    Bernie -- You can do anything you want. Uniform wall thickness is desirable only because otherwise the turned object's weight may feel 'off' in your hands. Humans are very good at how much an object will weigh before we pick it up. If a bowl's walls are thin on top and thick on the bottom, the bowl will feel heavy. (Sometimes that's desirable. More often, it's not.
    Richard Raffan has some what I think is great advice in his book Turning Wood. When turning bowls and such if you find that some feel better or worse in the hand than others, consider doing the unthinkable: he says "it pays to cut bowls in half occasionally--even very good ones--so you can see and analyze the cross section" and "to see if you actually turned what you think you turned ... often a sobering experience!" (page 167 in his 2001 and 2008 editions)

    I personally prefer to leave the bottom a little thicker because I like the way it feels and can add stability (if the foot is not unreasonably small diameter). I've even made some pieces quite thick on the bottom. For me, it's more about the balance than the weight. The intended use might make a difference - I turned a thin and relatively light bowl for my Lovely Bride's popcorn while watching TV, but like a heavier piece that sits on the table for fruit and such.

    Note that turning the bottom considerably thicker than the sides is fine for dry wood but can lead to cracking with green wood.

    Everyone's different but I'm not sure if I'm much "good at how much an object will weigh" before I pick it up. Some of that might depend on the type of wood, say Cocobolo vs a lighter weight wood such as Red Maple. I've gotten surprise and positive comments on pieces that are quite heavy due to dense wood and a thick base.

    JKJ

  5. #5
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    I f read correctly what is being said, the shape and wall thickness is an esthetic choice. Evenness or uniformity of wall thickness and shape does not create stress movement or problems in the future.

  6. #6
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    Quote Originally Posted by Bernie Kopfer View Post
    Evenness or uniformity of wall thickness and shape does not create stress movement or problems in the future.
    Not once the wood is dry, and assuming that the bowl is not exposed to extremes of moisture/heat over short periods of time.

  7. #7
    I green turn everything to final thickness and let them warp, and the more they warp, the better they seem to sell. For a finished bowl, I go for about 1/4 inch thick. Some times a tiny bit less, and with some woods, I will go to maybe 5/16 but seldom 3/8, as those just don't feel right to me. This weight and wall thickness just feels 'right' to me. Mine are all intended for daily use. I do not like the feel of rims that are slightly undercut, which some say helps you get a better one handed grip on the bowl. I go for uniform thickness all the way through. The only thicker part is in the transition area. I try to make the bottom center the same thickness as the walls. I did go through a phase where I was turning as thin as possible, but didn't like having to weigh the bowls down when doing outdoor shows. Fortunately I was making juggle balls and Hacky Sacks at the time, and they were nice soft weights.

    robo hippy

  8. #8
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    Quote Originally Posted by Reed Gray View Post
    ...For a finished bowl, I go for about 1/4 inch thick. Some times a tiny bit less, and with some woods, I will go to maybe 5/16 but seldom 3/8, as those just don't feel right to me. This weight and wall thickness just feels 'right' to me. ...
    And these wall thicknesses are on what sizes of bowls? 4" diameter? 24" diameter? Seems it would make a difference.

  9. #9
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    I consider even wall and bottom thickness as good insurance from any movement issues over the life of the bowl. Wood moves over it's life, especially if a thin oil finish like walnut oil is used. Walnut oil doesn't slow moisture absorption much at all. Personally, I see no advantage of having a heavy bottom. It's not like it has to maintain a balanced position sitting on a table.

  10. #10
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    Quote Originally Posted by Richard Coers View Post
    I consider even wall and bottom thickness as good insurance from any movement issues over the life of the bowl. Wood moves over it's life, especially if a thin oil finish like walnut oil is used. Walnut oil doesn't slow moisture absorption much at all. Personally, I see no advantage of having a heavy bottom. It's not like it has to maintain a balanced position sitting on a table.
    Might depend on the shape and design as well as the wood and finish. I can only say these pieces are made with very thick bases and after years I have never had a wobbly base from movement even when moving them to different environments. Usually 10 coats of "danish" oil, basically BLO and poly. Not exactly bowls, though. Maybe I'm just lucky.

    penta_platter_bowl_IMG_7440.jpg penta_plates_comp_small.jpg

  11. #11
    Wall thickness varies according to wood species, and not size. Pacific Madrone, which warps more than any other wood I have seen except possibly sycamore, I turn a bit thinner, 1/4 or less. Maple or walnut, which are very stable woods, well especially when compared to Madrone, I leave a bit thicker, like 5/16.

    Side note on warping with Madrone, it is totally unpredictable. I can compare cores after they are dried, and some times they will warp the same way, and some times not. Sycamore, while it moves a lot, it is predictable.

    robo hippy

  12. #12
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    Quote Originally Posted by Reed Gray View Post
    ...
    Side note on warping with Madrone, it is totally unpredictable. I can compare cores after they are dried, and some times they will warp the same way, and some times not. Sycamore, while it moves a lot, it is predictable.

    robo hippy
    Do you use boiled Matrone? That I have, boiled and air drying or dried, seems quite stable.

    JKJ

  13. #13
    Never tried it. A couple of reasons. One is with the volume of bowls I was doing, it wasn't practical. I would have needed a horse trough and a couple of big propane burners. The boiling tends to muddle the colors together, which I don't like. Also, the more warped the bowls are, the better they sell for me. Just me being different I guess. The madrone turns like butter. Only comparable woods I have turned are green dogwood, and pear. Smooth even grain.

    robo hippy

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