Turning Green Wood Bowls The Process

Turning Green Wood Bowls – The Process

Turning green wood bowls is one of the most satisfying experiences imaginable. Taking a freshly cut piece of timber and turning it into a form, a creation to enjoy, use, and admire, is the ultimate gratification.

Wood is an ever-changing, dynamic material. Raw timber, green wood, is the blank canvas of bowl turning. Whether it’s a small branch or an entire massive tree, all wood bowls start with some type of raw forest material.

And as woodturners, we need to understand this dynamic material to harness its possibilities and not become surprised or potentially humiliated by its realities.

It is up to us to apply our vision to see the potential that lies in each grain-filled specimen and bring it to a new life as a functional or decorative turned piece.

Wet and Dry

There are two broad categories of bowl blanks, green or wet wood and dried bowl blanks. As most woodturners don’t have access to kilns or dryers and purchased dried blanks are usually expensive, meaning more than free, we will be discussing the fine art of turning green wood bowls on the lathe.

Turning green wood is not without its drawbacks and quirks. In this article, I will share with you what I’ve learned about turning green wood bowls, both acquired knowledge and first-hand experience.

What is Green Wood

Before we go too far, it makes sense to define green wood. Some people, define green wood as only freshly cut wood that comes from a recently growing living tree. That type of green wood is usually dripping with moisture, especially if harvested in the spring or summer months.

Any wood that is not seasoned and noticeably moist is considered green wood. This may be wood from a just fallen tree or a log that has sat for some time. Wood can hold moisture for very long periods of time after being cut or downed.

This may sound silly, but virtually any wood that is wet and not dry is green wood. Wood that can still lose excess moisture is green wood. It’s really that simple of a definition.

Dry Wood Understanding

With either the passage of time or the use of a kiln, wood is dried or seasoned. When the amount of moisture in a particular piece of wood is reduced to the point where no more moisture can be moved out of the log, this constitutes dry wood.

Wood will become “dry” by letting it sit for a long enough period of time. A rule of thumb that is thrown around often is one year of air drying time per one inch of wood thickness.

A dryer or kiln can be used to reduce the moisture content more rapidly. Another alternative, a microwave can aide in this process by methodically heating the wood-locked moisture which forces it to escape in the form of water vapor.

Equilibrium

Did you notice the definition of dry wood above? “When the amount of moisture in a particular piece of wood is reduced to the point where no more moisture can be moved out of the log,” does not mean the wood is 100% moisture free. Why is this?

Everything everywhere is relative. Wood is somewhat like a sponge. It will absorb and release moisture forever. Yes, I said forever. Some woods do an excellent job making us think they are not moving and shifting because of moisture content, but they are.

Instead of thinking of “dry wood” as a static final resource material, think of it as a flexible, moving sponge. The cells in wood continue to absorb relative humidity in the air, and they also secrete moisture when the surrounding relative humidity is low.

Wood is a dynamic changing material that can be turned and made into beautiful creations, but we need to be mindful that it is not a static, fixed material.

Conditions and Climate

It would be really nice and straightforward to be able to say something generic and universal like, “once the wood is at a moisture content of, say, 12% it is then dry.” But, that may or may not be true for where you live, the season, or the type of wood you’re turning.

A wood bowl blank sitting on a shelf in North Carolina might be considered “dry,” while the same bowl blank sitting on a shelf in Phoenix may continue to lose moisture and change shape for some time. It’s all relative.

Moisture levels in wood are subject to change with the surrounding climate and conditions. Because of this, there is never a straightforward answer to the many questions that arise about the “drying” process of green wood. But there are many indicators that we can use as guides along the way.

Why The Fuss

What’s the big deal about moisture content? Moisture in the wood cells helps define the shape of those wood fibers. And if the form of those cells can be changed, the entire chunk of wood can, therefore, be changed as well.

When a fluctuation in a wood’s moisture content occurs, the wood moves. This movement can be subtle or dramatic. When the timber is cut, the tree can no longer move moisture the way it did when it was living. Basically, a cut piece of wood is exactly like a kitchen sponge.

If a kitchen sponge is wet, it expands and fills its cells with water. The same kitchen sponge left on the counter to dry will contract, shrink, and pull together in a tightly curled shape. Expanding and contracting is essentially what wood does as well, forever.

Turning Green Wood Cell Moisture Movement

Turning Green Wood Cell Moisture Movement

Cracking

The worst offender when turning green wood bowls is cracking. Cracks occur when the internal pressures in the wood structure dry unevenly. A bowl wall that was turned thin at the rim and thicker at the base cannot move moisture in and out evenly. This stress between too uneven regions usually causes cracking when the bowl is left to dry.

Turning Green Wood Bowl Cracks

Turning Green Wood Bowl Cracks

Cracking occurs based on the organic structure of the tree and the different areas in the log under various pressures, as well. The pith area of a log is especially prone to cracking. All the surrounding wood layers pull and push from this core.

While some cracks in wood bowls can be fixed, it’s usually best to try to avoid them all together in the first place. Even and consistent wall thickness when turning green wood is the key to reducing the chances for cracks.

Pith In

While the pith can be left in a green wood bowl turning, it really needs to be carefully handled. I would suggest positioning the pith, if left in the bowl, down the side of a bowl and not along the rim edge.

The most important aspect of green wood bowl turning with or without the pith is to make the bowl walls even throughout. It doesn’t necessarily matter what the wall thickness is, just that it is even throughout from rim to bowl bottom.

Shape Shifting

As the kitchen sponge image above illustrates, the shape of a green wood bowl turning will change as well. It is merely the nature of working with green wood.

When you make a green wood bowl, it is important to realize that changes to the bowl shape will occur as the bowl’s moisture content moves towards equilibrium. Do not have unrealistic expectations of a perfectly round-rimmed final bowl. That is not what happens when turning green wood bowls.

A simple round turned traditional bowl will most likely elongate a bit and distort as it drys. Usually, the rim will have elevated areas that form near the pith on each side of the bowl rim. This is the natural movement of the wood grain as it drys.

Turning green wood bowls relatively thin can cause warps, waves and dancing wood during and after the drying process. I’ve seen some that have very little roundness to them once their moisture equalizes. It’s hard to picture they were ever attached to a lathe at one point.

This is all part of the fun of green wood bowl turning. However, if you’d like to use green wood to make more precise predictable final forms, be sure to read the green wood twice turned section below.

Species Specific

To add to the unpredictability of turning green wood bowls, each tree species behaves differently than one another.

For instance, cherry can be super finicky and is ready to crack if you look at it wrong. While hickory is usually rock hardwood that can be shelved for years and turned crack free usually.

Each species of tree grows, forms, and develops differently. For example, the Eucalyptus is said to pull microscopic grains of soil with silica into its cells as it grows. This can potentially be hard on steel tools, but how does that affect the wood’s structure? Each wood species is different and will behave differently.

Turning Green Wood Bowls – 4 Things To Consider

Green wood is genuinely satisfying to work with. Long curling shavings glisten with moisture and fall to the floor leaving little or no dust. At times the wood seems to cut like a bar of soap, effortless and smooth.

It is important to remember the characteristics of this wet wood. The green wood can be spongy, and there are particular things to consider while turning.

  1. For instance, the tenon or mortise on the foot of a bowl will have a bit of give so its essential to size and shape the tenon or mortise carefully to maintain the best grip.
  2. If a faceplate is being used, it’s not a bad idea to use a bit longer screws to create a better grip as these too can work their way out of the soft, moist wood.
  3. Because the wood is sensitive to quick changes in moisture content, it’s essential to completely turn the piece you’re working on within a relatively short period of time. In other words, if the outside of the bowl is turned and you decide to wait until tomorrow to turn the inside, you may return to find all kinds of nasty cracks and checks especially along the end grain of the bowl.
  4. Many people think you can not sand green wood. I’ve found this not to be true. Now, if the surface is dripping with water, yes it will be difficult because sanding will mostly make a slurry that will plug up the sandpaper. If the wood is really wet, I’ve found waiting ten minutes or so allows the surface to dry just enough to let the sandpaper to do its job. I also use mesh sanding disks that can be cleaned quickly and don’t allow the debris to build up as much as traditional sandpaper.

Turning Green Wood Bowls Experiment

If you are like me and you have many different growing timber species available in your local area, consider conducting this experiment the next time you land a pile of turnable wood. Take an available log of one species, ideally one that is typical and average from a pile of similar logs, and make several bowl blanks.

On the lathe, turn sample bowls to determine how the green wood will behave. Turn a thin walled bowl, a medium thick walled bowl, and a thicker bowl. Let the bowls air dry or place them in paper bags with fresh shavings.

What happened to each of the different bowls? Did cracks form, and if so where were the cracks? Did the wood move, warp, wave, or deform, and which thickness bowl moved the most?

You may be surprised to discover, that these results are most likely typical for that species of tree and if you did your test again on an entirely different tree of the same species, you’d probably see similar results.

Turning Green Wood Bowls Thin

Turning green wood bowls thin walled can be a lot of fun. Not only does the wet wood cut smooth, crisp, and relatively dust free, light easily passes through the thin moisture wood fibers.

Place a light source behind the bowl once the wall thickness has been reduced and you can use the resulting brightness as your wall thickness gauge. If the light shining through the bowl wall becomes brighter, the wall is getting thinner. Ideally, a continuously even lit appearance down the bowl wall is the goal.

Also, when turning very thin-walled green wood bowls, the amount of area to hold moisture has dramatically been reduced. This means the green wood will dry very fast, so you need to work rapidly. Spraying a mist of water from a water bottle sprayer on the wood at regular intervals will prevent the wood from drying prematurely as you work.

Turning Green Wood Bowls Thin

Turning Green Wood Bowls Thin

Turning Green Wood Bowls Medium Thick

The green wood medium walled bowl is an excellent test for a tree species. Turning green wood bowls about a half-inch to three-quarters of an inch thick are usually pretty stable. Again, even wall thickness is the key to preventing too many surprises and nasty cracks.

Medium thick bowl walls typically have good structural support for the bowl’s shape, and they release moisture content slowly over a more extended period of time, which eases the bowl into it’s equalized form more gracefully.

However, again, it’s all about the species and conditions. Where medium thick walled green bowls are fantastic for one species, they may not work at all for another tree species. The importance of experimentation can’t be underestimated.

Turning Green Wood Medium Thick Bowl

Green Wood Twice Turned

Turning Green Wood Bowls Twice Turned

Turning Green Wood Bowls Twice Turned

Turning green wood bowls twice always reminds me of twice baked potatoes. And the process is very similar in a few ways.

The principal behind twice turning green wood is first to create a rough bowl shape that can dry and reach equilibrium before being turned a second time to the final finished shape.

We know that green wood is going to move, shift, and reshape as it dries. The first stage of twice turnings accounts for this by removing the mass of the wood and creating even walls to allow even moisture to escape.

Then the second stage of the twice turned wood bowl takes advantage of the fact the wood is now much more stable to make a more dependable shaped final bowl.

How to Twice Turn A Green Wood Bowl

To size the first rough turning for a twice turned green wood bowl, the rough wall thickness is critical. The rule of thumb is the wall thickness needs to be about ten percent of the overall bowl diameter. So a 10” wide bowl should have a rough wall about 1” thick.

Why such a thick wall? As the bowl deforms in the drying process, the pith ends of the roughed bowl will stretch and elongate typically. As this happens, an oval is formed. Having the thick walls will allow enough material to second turn a true round exterior circle and then a final inner circle.

If the walls of the twice turned roughed bowl are too thin, the second turning will cut through the more extended areas and destroy the bowl. There just would not be enough material to reveal a final round shaped bowl.

On the other hand, if the bowl is made too thick, it will take too long to dry, and they will merely be excess material to turn away needlessly.

Turning Green Wood Bowl Benefits

You may be thinking, with all these factors and nuances to consider, why even bother with turning green wood? After all, purchasing a nice clean, dry bowl blank is nearly effortless.

This is true, but there are many drawbacks to buying prepared dry bowl blanks, including excess dust, predetermined wood cuts, and the expense.

Using green wood for wood turned bowls has so many advantages.

First of all, green wood is everywhere around and usually free for the taking. Recycling a fallen tree is a whole nature-soaked interactive process with our environment.

Creating green wood bowl blanks is a gratifying and satisfying process. Not only does it help someone clear what they may consider waste debris, but it also yields lasting heirlooms of beauty when turned into wood bowls.

Green wood is usually free. How many things in life are reliably free and plentiful? Not too many. With a little exploring, there are numerous ways to acquire free wood to turn bowls.

Green wood, in most cases, was headed for a different demise of rot, compost, mulch, or worse yet, fire. Think of saving and using green wood as a rescue and recovery mission. This would be funny if it weren’t true. The number of beautiful wood species trees that go to waste is astonishing.

Turning green wood is a fantastic experience on the lathe. Many species of timber, in green form, turn buttery smooth and surrender gracefully to the bowl gouge.

Wet green wood turns more efficiently and cleaner than dry wood. Free flying dust is reduced making the air a bit safer to breathe. Shavings from green wood come off large and curly producing little or no dust. The moisture in the wood has the added benefit of cooling the tool’s cutting edge helping it stay sharp longer.

My favorite thing about beautiful free green wood is you never know where it will come from next and what species it might be. It could be a storm that makes literal tons available, or a friend calling to let you know about a recently removed specimen.

Heck, even driving becomes more interesting when you’re on the lookout for new turning material. I’ve stopped randomly many times to chuck logs from ditches into my trunk.

When collecting, cutting green wood bowl blanks, and turning green wood, we the creators of the final wood turned bowls, get to decide where we would like to cut the wood and in what direction and to what final size. We are engaged in the entire process from the source to the final turned piece. This is not possible when purchasing dried bowl blanks, as someone else has already made all those decisions long ago.

Turning Green Wood Bowls – Conclusion

Turning green wood is a hands-on process that places the woodturner in charge and at the helm from start to finish.

Massive amounts of experiential knowledge are gained when turning green wood bowls. Turning skills specific to each tree species become engrained into our hand, eye, and tool coordination.

In many ways, we truly honor the very nature of the tree as we gracefully and elegantly lift it from the process of decay and set it on the stage of appreciation, for generations to come.

Leave a Comment