[Woodworkers] Turning Burls

Richard Allen rla_buy at yahoo.com
Fri Dec 31 16:39:25 PST 2021

Hi Chuck,

Turning a burl is a lot of fun.  Turn it wet.  Your choice is to turn it thick and dry it slowly or turn it to finial thinness (1/4” or less and an even wall thinness) and dry is slowly.

Drying slowly can be done several ways.  If you want to preserve a natural edge then the drying process is more limited.  You can’t use anchor seal (emulsified wax) to slow the drying process because you can’t remove that stuff from the natural edge.  The two methods I have used are:

Put the turning in a brown paper bag along with some of the wet shavings.  At some point you will need to remove the wet shavings but you can keep the turning in wet shavings for weeks without degrading the wood.  Once you eliminate the wet shaving put the turning is a brown paper bag along with one or two paper towels.  Every day remove the turning from this bag and put it in a dry bag along with dry paper towels.  Turn the wet bag inside out and hang up the wet paper towels.  These wet things will dry and you will use them the next day. You may need more than two sets of the bags and paper towels.  Keep doing this daily routine until the paper towels come out dry.  Then switch to the exchange once every 3 or 4 days.  In a month you may find the wet paper towels can take a week to become wet.  At this point you can likely eliminate the paper towels  but keep exchanging dry bags weekly for a few months.  To tell if the turning has dried kiss the turning.  When you press your lips to the turning you will be able to detect if the turning is cool.  When the turning no longer feels cool by the kiss method you can feel confident that the turning is dry.  I would leave the “dry” turning out of the bag for a couple of weeks to insure it is indeed dry.  At that point you can return the bowl if you left it thick or hand sand if you turned it thin.  Expect the drying process to take  few months if turned thin.  Expect the drying process to take 6+ months if turned thick.  I know this all sounds like a lot of work but it is actually a lot of attention and very little work.  If you try to rush the drying process you will less success.

If you turn thick then the wall thickness hound be even from rim to bottom and at least 1” thick.  The rule is wall thickness of 10% of bowl diameter.  For a burl this thickness should be a little more (maybe 15%).  Please note that a 6” bowl should be 1” thick even though the 10% rule says the thickness should be less.  The primary reason for the thickness is that there will be enough wood when dry and warped that the bowl can be returned round.  The two benefits of thick turning are, the finished bowl will be round and you can sand on the lathe.  The detriment to the thick turning is that there are more failures in the drying process.

Please note that the chances of drying failure for unturned wood is very high.  Maybe a 20% success rate.  The success rate for thick turned bowls is dependent on the drying attention.  If good attention Is provided you should have 80% success.  BTW success with slow drying using emulsified wax coating is closer to 90%.  Success for thin turned bowls, given that attention is provided should be 85%.  Cottonwood tends to dry well and I would expect a much better Ives’s rate.

You can use a plastic bag instead of a brown paper bag.  The process is a boy longer and the success rate is higher.  Starting with a plastic bag for the first couple of weeks can help.

I would turn between chuck face and live center.  This gives you the most positioning options.  Note that burls tend to follow a cone shape with the wide part of the cone being at the bark and the point of the cone being towards the center of the tree.  You want to preserve as much of the burl as you can.  So the bottom of the bowl should be the bark side and the top (opening) of the bowl should be the center of the tree side.  There is some variation in the internal shape of the burl and cotton wood tends to be more ball shaped and less cone shaped.

As I said the blank starts out between the chuck face (not clamped by the chuck but pressed against it) and the live center.  Start with the bark side toward the live center.  Adjust the mounting so that the blank runs mostly balanced.  Turn the blank round and put a foot on the live center side.  That foot will be clamped into the chuck in the next stage.  
Once mounted in the chuck use the live center for support and turn a foot on the bowl mouth side (live center side).  You will now have the blank with tennons on the foot and in the bowl.  Now mount the blank on the tennon on the bowl mouse side.

Again use the live center for support.  Turn the outside of the bowl, removing the live center once you have established most of the outside shape so that you can refine the tennon that will be the foot of the bowl.  If turning thick do not turn away the dimple left by the live center as that well help when mounting after drying.  If turning thin make the bottom mostly finished.

Now mount the bowl on the foot tennon in the chuck and hollow out the bowl.  Remember that an even wall thickness will help to yield success in the drying process.  As this is wet wood you should turn the bowl all at one time.  A wet bowl sitting on the lathe overnight will almost certainly develop cracks.  You can wrap the bowl in plastic if you must walk away for  couple of hours.  You can remove the wet bowl from the lathe and store in a pile of wet shaving overnight.  Please note that remounting the wet bowl the next day will present some “challenges”.

If you can live without the “natural” edge the turn are described thick and put a coat of emulsified wax on all surfaces.  Put the waxed bowl in a cool dry place out of sunlight.  Leave the drying blank undisturbed for several months.  Use the kiss method to determine dryness.  Turn the thick bowl round but not to finish thickness and let sit for a couple of days.  If the bowl remains round it is dry.  If the bowl goes oval leave it to dry more for at least a month, two months would be better.

I know this is a LOT of info and I am sure I am missing many critical parts of the process.

I can always try to clarify anything I have mentioned.

Turning a green burl and turning green wood is more the same than it is different.

> On Dec 31, 2021, at 5:42 PM, chuck.steger--- via Woodworkers <woodworkers at lists.sawdusters.org> wrote:
>    Happy New Year to everyone! I hope your holidays were good! Mine sure were. 2021 was a year of turning first for me … I turned copper (with help from this wonderful group), I turned finales & icicles out of resin for my Christmas ornaments, and did the same using shop-made turquoise finales & icicle tips.  Now, I want to try turning a burl.
>    I cut a burl a few days ago from (I think) a cottonwood tree. Cottonwood is a softwood so not sure if that matters. Would appreciate some guidance on:
> Turn green or dry?
> From what I understand, if you turn green, it’s easier to turn. You then have to dry it where it could warp. Some people leave the warp (or crack) and some fill cracks and turn round when dry.
> How long will it take to dry?
> Wall thickness if re-turning? Wall thickness if not? Or, is that hard to say until you see it dry?
> Advantages to turning dry? Anything special to do when drying.
> The bottom is rough from the chain saw cuts so I need to flatten, right?
> Face plate or will a screw chuck work?
> Anything else I need to know? I’d like to do a natural edge type bowl.
>    As always, thanks!
> Chuck
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