Leylandii / Leyland Cypress - bowls & knots?

[Steve Martin]

Looking at your photos, such as the ones of March 27, I believe you left the heart wood in your piece. In my experience, leaving the heart wood virtually guarantees splitting.

[ToneWood]

Hi Steve, thanks for the comment although I am rather confused by it:
March doesn't appear in this thread, do you mean May 27th, the near finished Leylandii bowl and/or new oak blank or do you mean the initial bowl shots April 14th?

How/where do you define heartwood? Do you mean like the dark area in the oak blank for example:

I see that is how wiki defines it: http://en.wikipedia.org/wiki/Wood#Heartwood_and_sapwood Perhaps you mean the pith - the small very soft bit in the centre?
I removed the pith. I often leave a little pith in at first (1-2mm), because I know I will have to remove more later during the bowl making process (esp. when hollowing, flattening the top & finishing).

You have to use the heartwood, for example, in the piece of oak above, it's the majority of volume including all of the middle wood- otherwise you'd just end up with a curled platter/half-pipe with no ends. For a reverse bowl, most of the middle of the bowl including the base will be heartwood. Also, for oak at least, the sapwood is often softer and less reliable/consistent than the heartwood (as defined above). Wiki actually makes some mention of this:

Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.

I gather near the root of trees (which is where the biggest blanks would often be found), the center is often soft/rotten/diseased - but that wasn't the case here.

Re. "leaving the heart wood virtually guarantees splitting." I've made several other bowls the same way (& the reverse way) and have not experienced significant splitting before. Also, while the split I refer to is near the center of the handle (heartwood), a small, earlier split occurred at the edge of one handle (made a rather nice repair of that one). But I'm open to enlightenment.

[ToneWood]

Another interesting wiki-link on wood drying: http://en.wikipedia.org/wiki/Wood_drying It has some info. of splitting during drying:

Reasons for splits and cracks during timber drying and their control

The chief difficulty experienced in the drying of timber is the tendency of its outer layers to dry out more rapidly than the interior ones. If these layers are allowed to dry much below the fibre saturation point while the interior is still saturated, stresses (called drying stresses) are set up because the shrinkage of the outer layers is restricted by the wet interior (Keey et al., 2000). Rupture in the wood tissues occurs, and consequently splits and cracks occur if these stresses across the grain exceed the strength across the grain (fibre to fibre bonding).

The successful control of drying defects in a drying process consists in maintaining a balance between the rate of evaporation of moisture from the surface and the rate of outward movement of moisture from the interior of the wood. The way in which drying can be controlled will now be explained. One of the most successful ways of wood drying or seasoning would be kiln drying, where the wood is placed into a kiln compartment in stacks and dried by steaming, and releasing the steam slowly.

[Steve Martin]

Greetings! Yes, I mis-stated the date and the name (location) of the wood I was referring to. Went back and looked at photos again and noticed that, what I erroneously called heartwood but meant pith, in several photos on April 14 and May 4,13,20 and 27. As I remember, it is a small dark circle about 1/3 down from top edge on inside of bowl. You are correct that eliminating the heartwood would not leave much to work with. I apologize for the temporary (I hope) brain fart.

After thinking more about it, I would like to add the following. My understanding of the splitting phenomenon is that splitting is primarily due to loss of moisture by cells toward the outside of the piece, away from the pith, before/faster than the cells closer to the pith losing their moisture. As the cells in the outer growth rings lose moisture they occupy less space than the growth rings toward the pith which haven't lost as much moisture. Because they occupy less space than they used to occupy, something must give, and it does give, ergo! a split which increases because the split encourages more loss of moisture from the cells along the split. I realize that other factors, including growth stresses, lack of or surplus of moisture during specific growth periods, how the wood is handled after the tree is cut before it gets to the bowl maker/carver, exposure to sun and wind, etc. all can influence splitting.

When carving spoons out of native cherry that grows here in North Carolina, I have had the piece split while I was carving, usually overnight when I couldn't finish the spoon in one sitting. Later, after finishing the spoon, I put it in the microwave and finished drying it. The splits closed up with no gluing or other encouragement on my part. This has also happenend with native maple. My attempt to explain this is that when the moisture is evened out throughout the piece so that the outer growth ring wood RELATIVELY takes up the same space/area/volume compared to the wood underneath it while they were both filled with water/sap, toward the pith, there no longer needs to be a split in the outer wood. Have a great day!

[ToneWood]

Greetings! Yes, I mis-stated the date and the name (location) of the wood I was referring to. Went back and looked at photos again and noticed that, what I erroneously called heartwood but meant pith, in several photos on April 14 and May 4,13,20 and 27. As I remember, it is a small dark circle about 1/3 down from top edge on inside of bowl. You are correct that eliminating the heartwood would not leave much to work with. I apologize for the temporary (I hope) brain fart.

Oh, I see what you mean, it does look like it might be pith doesn't it - it's actually a knot. The wood was split along the grain, so if it were pith it would appear in both ends - and would be very soft rather than hard (which it is).

Also, I split the bowl blank through the center pith - it's part of Jogge's process that I try to follow - and I can normally see the pith running right down the middle of the split blank. It's not obvious in the Leylandii blank but can be seen clearly in the oak blank above.

After thinking more about it, I would like to add the following. My understanding of the splitting phenomenon is that splitting is primarily due to loss of moisture by cells toward the outside of the piece, away from the pith, before/faster than the cells closer to the pith losing their moisture. As the cells in the outer growth rings lose moisture they occupy less space than the growth rings toward the pith which haven't lost as much moisture. Because they occupy less space than they used to occupy, something must give, and it does give, ergo! a split which increases because the split encourages more loss of moisture from the cells along the split. I realize that other factors, including growth stresses, lack of or surplus of moisture during specific growth periods, how the wood is handled after the tree is cut before it gets to the bowl maker/carver, exposure to sun and wind, etc. all can influence splitting.

That makes sense to me, that is pretty much how I think of it currently. I suppose the trick is to dry it slowly, so that moisture is able to work its way from deep inside to the outside without the outside drying out. It makes me wonder if having a bowl where all parts are roughly the same thickness (and relatively thin) might help avoid splitting.

When carving spoons out of native cherry that grows here in North Carolina, I have had the piece split while I was carving, usually overnight when I couldn't finish the spoon in one sitting. Later, after finishing the spoon, I put it in the microwave and finished drying it. The splits closed up with no gluing or other encouragement on my part. This has also happened with native maple. My attempt to explain this is that when the moisture is evened out throughout the piece so that the outer growth ring wood RELATIVELY takes up the same space/area/volume compared to the wood underneath it while they were both filled with water/sap, toward the pith, there no longer needs to be a split in the outer wood. Have a great day!

That is interesting. It occurred to me that just letting the thing dry slowly (the bowl is back in the garage) should close up the crack when everything becomes equally dry - but I figured there would still be a fine open crack. In your case, I wonder if the internal heat generated by the microwave might have melted/softened something glue-like in the wood (Lignin* or resin** perhaps)?

*Somebody recently posted a link on boiling (turned) bowls to relieve stresses - apparently it is thought to reduce/eliminate cracking. The article hypothesized that is might be due to thermo-softening and then resetting of the Lignin. I didn't have anything near big enough for this big bowl but I did try soaking it in hot water in a big Belfast sink - using hot tap water and several kettles full of boiling water - but clearly it didn't help/wasn't enough in this case.

From wiki:

In 1998, a German company, Tecnaro, developed a process for turning lignin into a substance, called Arboform, which behaves identically to plastic for injection molding.

**Leylandii contains/produces resin - you see blobs of it sometimes and my hands were sticky after handling a lot of it (would be great for rock climbing - some French & Californian climbers use violinists' roisin/rosin to keep their hands dry and tacky). Perhaps I should see if I can find some, warm it up and use it to glue the sea?. Unfortunately we don't have a microwave, let alone one big enough for this bowl

[Steve Martin]

Tonewood, I think that microwave ovens work by heating the water in whatever is being cooked because the frequency of the micro wave is the frequency that excites the water molecule, heating it. This happens wherever the water is, in what is being "cooked". Therefore, the water at the center of the piece gets excited, ie., hot and exits the cells at virtually the same time that happens in the outside layers.

There is a woodturner in Texas, whose name I can't remember, who has been collecting info from turners around the world for several years about boiling wooden objects to "cure" or "dry" them but I have not seen any recent written reports on his findings. There is a company in Whiteville, NC that rescues timbers from the bottom of the Cape Fear River. As an aside, some of the found timbers have had an English royal mark on them from the 17th Century. I have heard reports from the company that they have very little problem with subsequent splitting of their sawn lumber. I have also read reports of early (17th and 18th century) settlers, clearing land for a house, barn or field, when they would fell a tree they would like to use for furniture or some special purpose, but because of the pressure to get their land cleared would roll the log to the closest body of water and submerge it until they could get to it, maybe 2-3 years later. Supposedly, they had fewer problems with splitting than they might have had when that wood was first cut.

One theory is that the fresh water replaces the sap. Somehow that allows the wood throughout the log to reach some kind of equilibrium that results in subsequent sawn or rived wood having less problems with splitting while drying. I suspect our woodworking ancestors had a lot of knowledge about the behavior of wood in many circumstances, which they didn't necessarily have a scientific understanding of but which they knew what happened and what they needed to do to either compensate for that reaction or how to use the reaction to their benefit. We have lost a lot of that knowledge and only through sharing through this, and other, forums will we relearn it and share it.

Sorry this got so long.

[ToneWood]

Very interesting. I'm learning by trying all sort of things, you tend not to forget the lessons learnt that way but it's a slow & expensive (in time & effort) process! I think you are right, much knowledge is lost over time.

[ToneWood]

Oiled bowl:

Smoother than I originally expected and consequently feels very nice.

Leylandii bowl - oiled fireplace.jpg (71.85 KiB) Viewed 12421 times

The first coat of linseed oil on the pale/white bowl made the grain spring out and caused the natural red tinge the wood to glow through the warm yellow of the linseed oil. I was well pleased but apparently the wife liked the original pale whiteness of the bowl, so I decided to hold back on the linseed on subsequent treatments, using walnut oil instead.

Leylandii bowl - oiled table.jpg (82.21 KiB) Viewed 12421 times

I suppose one doesn't have to oil wooden bowls at all: many old wooden bowls (e.g. dough bowls & the elm bowls of the Bucklebury turner, George Lailey) were used dry.
BTW I have moved this bowl indoors again now, after its extended stay in the coolness of the garage; the oil should help ensure that any remaining moisture is released very slowly.

[ToneWood]

Added my 2013 maker's mark. Was hoping to make this small & simple but the year date ended up much larger than planned due to coarseness of grain. I plan to simplify my mark further but will wait until next year before changing it again. And I will forgo the year date in future, as the mark is changing each year currently anyway, so it is unnecessary & my production volume is v. low.

Leylandii bowl mark.jpg (56.66 KiB) Viewed 12345 times

I added the year in Roman numerals (MMXIII=2013), as I believe they were designed to be carved (in stone). I experimented a bit, I cut my mark with an lovely old veiner gouge and the numerals with a narrow, bevel chisel (a 50p Marples, England socket chisel, in excellent condition but missing its handle), as it worked much better than the veiner for the straight lines of the numerals.

[ToneWood]

Started a second, smaller Leylandii bowl - reverse-style. This split blank has been soaking outside most of the Summer as it was a bit dry & hard and I had other projects to do first (garden arch, bowl horse, oak bowl). I was concerned that this might harm the bowl (soaking the oak blank had caused tannin to leech-out and blacken the water & the wood) but actually it looks really fresh now and handles like fresh green wood .

The softened bark was easily peeled off by hand. The now we t & softened blank succumbed far more readily to my awesome little HK adze.

Leylandii bowl2 reverse - hollowed.jpg (72.28 KiB) Viewed 12141 times

The wood is quite knotty. I managed to cut a lot of them out - they are wet & soft - but several will remain in the final bowl.

Leylandii bowl2 reverse - hollowed & trimmed.jpg (58.56 KiB) Viewed 12141 times

I used my large HK bowl gouges mostly to refine the hollow but to reach the narrow bottom I used this vintage Ashley Iles curved gouge (15/16 sweep?).

Leylandii bowl2 reverse - tidying up the hollow.jpg (86.45 KiB) Viewed 12141 times

[ToneWood]

I removed the bulk of the outside wood with my Gransfors Swedish carving axe but switched to my Lidl axe for the final rough shaping:

Leylandii bowl2 reverse - axed.jpg (102.42 KiB) Viewed 12130 times

That splintery knot in the bottom could become a major problem.

Leylandii bowl2 reverse - axed bottom.jpg (95.86 KiB) Viewed 12130 times

Then finished reducing thickness with my large Swan DK, then my smaller more delicate Marples DK - both used mainly bevel-side down to prevent them burying themselves, which worked well. I adzed under the handles to reduce thickness and add some interest to the shape, then spoke-shaved the sides (Stanley 51 flat & curved based Record).

Leylandii bowl2 reverse - bottom 1st pass with large DK.jpg (85.96 KiB) Viewed 12129 times

I planed then spoke-shave the bottom - this could become a tricky area for finishing as there is a big splintery knot in the relatively small base and I didn't leave a lot of excess thickness in the base (I normally leave too much). I decided to round one end and put a very shallow curve - almost flat - back, reminiscent of the bow & transom of a boat - using the trusty old Mora 106 (about 1cm shorter than standard now - perfect!).

Leylandii bowl2 reverse - DK'd, shaved & trimmed.jpg (75.31 KiB) Viewed 12130 times

Now the bowl is in the garage, left to dry slowly for at least 2 weeks before finishing. The wood is very wet, so there is significant risk that it will split if it dries too quickly. So far (touch wood) this has gone much more smoothly that my last bowl (a large, rectangular, oak dough bowl, which now is lovely and smooth but I'm still tweaking the base - the oak was tougher to carver, coarse of grain & I had to remove tannin stains caused by soaking - a lot of work).

Note to self: no more oak bowls (Peter Follansbee had a point!), no more huge bowls, no more regular geometric shapes (but if you do, stick to the shape - no "free hand" alterations to increase depth/length/width/volume). More smaller, reverse-style bowls in softer woods.

[ToneWood]

I am very pleased with this second Leylandii bowl - it is thin, light, and the thickness is quite even.

Leylandii reverse bowl side.jpg (20.55 KiB) Viewed 12013 times

I used a different drying technique on this bowl, alternating periods of in-house & in-shed drying, so that it dried reasonably quickly w/o cracking.

Leylandii reverse bowl top.jpg (45.04 KiB) Viewed 12013 times

Since the above images I scraped the outside and gave it a just a quick, light sanding. The inside & rim have been very carefully & lightly scraped & sanded - in order to retain tool marks. I left it unoiled so that it remains pale/white & it is now being used by its new owners as to hold peaches while they ripen.