How do I start drying green wood bowls?
There are many approaches for drying green wood bowls once they have been turned or roughed out, including using paper bags, a microwave, kiln, denatured alcohol, even desiccant drying beads, or just simply waiting.
Inside Drying Green Wood Bowls
Unfortunately, that is not the nature of wood.
Fresh cut or green wood contains moisture. For that matter, even logs cuts years ago usually hold moisture to some degree.
This moisture inside wood can remain trapped or escape over time, based on many different factors. If not managed, uneven moisture movement causes stresses in the green wood and will likely change the overall shape of a turned bowl, or cause structural failure in the form of cracks, checks, and splits.
As we have covered in Turning Green Wood Bowls, the term “drying green wood,” is really not a thing. A more accurate term is “equalizing wood,” but since “drying” is what most people think and say, we’ll use the term “drying” to keep this simple.
Ultimately, we really want to control our green wood bowl turning to fit our specific needs. Once-turned and twice-turned bowls have different characteristics.
The quicker and more abrupt the drying process happens for once-turned bowls, the more chances there are for cracks and unpleasant results.
Waiting for full twice-turned bowls to dry is boring and forces us to wait to have the beautiful final turned bowl we are imagining.
With the following methods, we can manage the even moisture equilibrium within our drying green wood bowls.
If you’d like to learn all about the twice-turning process, be sure to read this article.
Green Wood Off the Lathe
It is possible to take a freshly turned green wood bowl from the lathe and place it on your shelf and it will dry fine without problems. However, this is the exception and will be highly dependent on several factors.
Drying Green Wood Bowls, Dynamic Contributing Factors Include
- tree species
- time since cut
- relative humidity
- air flow
- light sources
- heat sources
- bowl wall thickness
- bowl shape
To more closely control and ease the drying process we need to be aware of our enemies. The two biggest enemies are unevenness and environment.
If the wood is turned uneven, with thick and thin areas, it is almost impossible to dry these areas smoothly without tension and cracks forming.
Controlling the environment is critical to ease the process of drying green wood bowls. Specifically, humidity, heat, moving air, and light are the elements working against us obtaining a crack-free final bowl.
We must protect our new green wood bowl turning from these mean evil forces. The best way to accomplish this is to turn an even bowl shape and protect that turned piece afterward from the natural forces working in opposition.
Drying Green Wood Bowls Slow or Quick
When drying green wood bowls, we have two different routes to take.
The first route is to turn the wood once and ease the drying process, so the wood does not change too much or too quickly. We want to avoid causing cracks and splits.
With once-turned bowls, because the bowl walls are usually thin and will quickly leach out moisture and potentially dry uneven, we are trying to slow and even out the drying time.
The other route to take is to twice-turn the green wood, which we’ll discuss more in a moment. The first turning is deliberately oversized and designed to take the stress of change during drying.
While we still want a smooth process to a “dry” bowl with the twice-turned method, we are also usually trying to speed this method because the wood is thicker and will take much longer to dry naturally.
Drying Green Wood Bowls Once-Turned
A once-turned bowl is a piece of green wood turned into a bowl at final shape and wall thickness. After the turning, the initial form of the bowl is finished at that point. Now, nature takes over.
With a once-turned bowl, depending on wall thickness, the piece will dry, move and transform into its finished form as is dries. If the bowl is turned thin, it may shift, warp, and buckle much more noticeably. This can be a desirable or not-so-desirable effect.
Either way, a thin-walled bowl will dry quickly, usually within a few days, and reach its finished look in a short time. Very thin walled bowls can dry in a matter of hours.
It is not recommended to seal the end grain of once turned bowls. Since it won’t be turned a second time, removing the sealer can be difficult or nearly impossible without damaging the finished bowl. Sealing end grain is more important with twice-turned bowls, which we will cover in a moment.
Instead of sealing the end grain of once turned bowls, we need to slow the drying process by controlling the bowl’s environment. Using the paper bag method (below) and/or spraying the end grain periodically with water to keep the wood evenly moist are two such approaches.
Once-turned bowls tend to have a very organic, natural look to them with offset curves and rims that may rise and lower from side to side. This may or may not be the look you’d like to achieve for the final bowl.
Drying Twice-Turned Green Bowls
As the name implies, twice-turned green bowls will be turned twice. Why you might ask? To obtain a more accurate round shape for the final bowl.
The first turning of a twice-turned bowl will be allowed to thoroughly dry. In the process of drying the bowl will usually pull outward at the pith, contract on the sides and essentially stretch.
With the walls of a twice-turned bowl made thick, 10 percent of the overall diameter, there is wiggle room to “correct” this movement. I will also carefully make my tenon a bit larger so that it will still be held properly by the four jaw chuck when it’s trued up after drying.
Basically, we let the first turned bowl do all the warping, moving, and shaping, then, once dry, turn it a second time to the final shape and final wall thickness. Because the wood, after the first turning and some time, is dry or equalized, the amount of movement after the second turning is minimal.
All of the methods below will work for twice-turned bowls. Because of the thick walls of the first turned bowl, it’s a great idea to seal the bowl’s end grain with Anchorseal before starting the drying process.
Sealing the end grain of the bowl slows the amount of moisture leaking from the open end grain. The goal is to have a more even moisture loss from both the side and end grain.
Evenness is the key.
Final twice-turned bowls usually look perfectly round with clean circular rims and fresh, crisp lines.
DRY GREEN WOOD BOWLS – Six Methods
Method One – Hope and A Prayer
Take a piece of green wood and turn it into a finish shaped bowl or a rough-turned bowl. See, Turning Green Wood Bowls – The Process, for more about twice, or rough-turning. Set the turned bowl aside.
Again, remember every wood species is different, and all the external forces acting on that bowl are always present. Some woods are super cooperative, and you will have no trouble, while others species seem to crack when you look at them wrong.
The finished turned bowl needs to be reasonably uniform in thickness throughout. If, for example, the walls near the rim are thin and the base is thick, more moisture will remain in the base after the thin walls have dried and this can cause uneven stress to crack the bowl.
For a final turned bowl, think how the environment will affect the equalizing wood. A low, cool, dark, sealed cupboard will be a much better storage location than a countertop, in the sunlight, near a breezy open door or heat source.
Set the final turned bowl aside and hope for the best. In a few days or weeks, the results will be revealed. I’ve done this many times with success and several times with failure.
I have turned green wood and done nothing else to it afterward, with decent results. The bowls that come to mind were turned from two-year-old cut hickory, so, while green, the wood was much drier than when first cut with the chainsaw.
By the way, there are many aspects to making your chainsaw blade sharp at all times. Check out this article for all the tips to perfectly sharpen your chainsaw.
Another contributing factor is the nature of the hickory species, which is a solid and stout structure. Also, the hickory bowls were turned with walls about 1/4” to 3/8” thick, not thin and not too thick. Even though they dried fine without cracks, there was some movement, noticeably waves along the rims.
Method Two – Paper Bags To The Rescue
Yes, brown grocery bags work well to allow the wet green wood bowl to release moisture slowly and evenly over time. Because the paper bag breathes, it will gradually release excess moisture and progressively dry, exactly what we need.
The paper bag with wet fresh shavings makes a controlled micro-climate for our wet green wood bowl.
Simply collect some wet shaving from the shop floor, preferably the ones from the same bowl, and line a paper grocery bag. Place the bowl or roughed blank inside, cover the bowl with more wet shavings and fold over the bag top and loosely tape the bag shut. Put this is a cool dark area that has little air movement. A cabinet or cupboard works well.
This is an important note. Don’t place a green wood bowl in a plastic sealed bag. In moist locations with humidity, plastic bags will hold in moisture and most likely cause mold, bacteria and rot to form, not things we want for our beautiful bowls.
The exception to the plastic bag rule is severely dry, arid locations, such as the desert. In these locations, plastic bags are used to try to retain moisture in the green wood bowl longer and slow the evaporation process.
Everything is relevant!
For the rest of us, that live in areas where there is a fair amount of relative humidity in the air on a regular basis, paper bags breathe and help regulate the passage of moisture very effectively.
The moist, fresh shavings will slow drying but because they are surrounding the bowl, they aid in regulating or buffering the amount and speed at which the moisture leaves the green wood bowl.
After a week or so, it is a good idea to move the green wood bowl turning to a new fresh paper bag. You can check the bowl’s dryness when you move it as well. The fresh paper will prevent excess moisture build-up and reduce bacteria or mold formation.
Approximately every week or so, (days if the piece is thin) check the piece and see if it is drying evenly without cracks. Remove the shavings if they are dried up. Return the turned bowl to a new fresh grocery bag without shavings, close the top, and return it to a quiet area free from too much air movement.
Check the moisture content of the wood as we will discuss below and once it equalizes the process is complete.
Method Three: Kiln Drying
If you have access to a dryer or kiln, this can be a great way to dry twice-turned thicker green wood bowls quickly. However, again, I suggest experimenting with this process too. Every species will act differently. One bowl might dry beautifully in a dryer, while another may disintegrate.
A homemade kiln can be made out of an old refrigerator, an insulated cabinet, or a box made from foam house insulation.
Just cut a vent hole in the old refrigerator base and one in the top and place a light fixture with an incandescent light bulb inside. The heat from the light will slowly dry the wood bowl blanks.
A systematic approach for advancing lightbulb sizes can be used to increase the temperature slowly and gradually over the course of several weeks by using progressively larger bulbs.
Start with a 40w bulb, then a 60w and finally a 100w bulb. Check the moisture content of the wood with a moisture meter or weigh the pieces to determine when they have equalized.
Be careful, however. Keep in mind that quick, sudden, unstable changes in the wood structure are what will result in the most problems. So easy does it and the more even everything is along the way, the better.
This method is best suited for drying rough-turned bowls that will later be twice turned to their final shape and form. A kiln or drier can take the drying time for thicker twice-turned bowls from months or even years to only a few weeks.
Method Four: Microwave Green Bowl Drying
If your bowl or roughed blank will fit into the microwave and if your spouse approves or is unaware you may want to try this technique. A garage sale microwave, just for drying green wood in your shop might be a better way to avoid domestic disputes. Just saying. 😉
Microwave the turned bowl on high for a very short period, 20-30 seconds. After each session, remove the piece and set it out to cool for at least a half hour.
I place the blank on the counter in the kitchen and prop it up on a side so that most of the bowl has good air exposure. The heated bowl will lose moisture through evaporation, so it’s essential that all surfaces of the bowl breathe.
After at least a half hour of cooling, I pop it back in the microwave for another 20-30 second dose. Repeat this process eight to ten times until the moisture content equalizes and the bowl is dry.
Don’t be mistaken, this isn’t as fast as a microwaved meal, but still much quicker than nature ever imagined.
If you’re microwave drying a thick rough turned bowl, it may take a few more trips to the microwave until the wood equalizes, then you’re ready to do the final turning.
Microwave drying green wood bowls aren’t as fast as making a bag of popcorn, but it sure beats waiting years.
Method Five: Drying Green Wood Bowls in Denatured Alcohol
Soaking rough turned or finished bowls in denatured alcohol creates a chemical process that bonds alcohol to the internal water in the bowl’s wood cells. During the drying process, this mixture evaporates from the wood very quickly.
This process requires that the bowl is completely submerged in denatured alcohol. A resealable plastic container just big enough to hold the bowl is ideal.
High quality denatured alcohol can be purchased in gallon containers, and enough is needed to completely cover the whole bowl.
Soak the bowl for approximately 24 hours before removing the bowl from the denatured alcohol. It’s not a bad idea to let the excess denatured alcohol drip back into the container so it can be used again later.
After the excess denatured alcohol is no longer dripping from the bowl, place the bowl in a paper grocery bag and press the paper around the bowl snuggly. In my research, I found some people take the time to wrap the bowl in brown craft paper, taping it securely shut with tape, like a wrapped gift.
The time it takes the denatured alcohol and water mixture to escape the wood cells in the bowl will vary but can take from one to three weeks. Like, everything we’ve discussed so far, all the various factors will contribute in different ways to affect the drying time.
Once the wood does not smell like denatured alcohol, the process should be complete. Use the techniques described below to determine dryness or the equilibrium of the moisture content in the wood bowl.
While I have not tried this technique yet, it appears to be a viable green wood drying solution for both finished once-turned bowls and roughed twice-turned bowls.
Method Six: Desiccant Green Wood Bowl Drying
When I first learned of this process, I had to stop and try to figure out how to pronounce the word, “desiccant.” Desiccant defined, is a hygroscopic substance used as a drying agent. Think of the little silica gel packets that come in some product packaging to keep the product dry.
Yes, you can purchase large amounts of desiccant and use it in the process of drying green wood bowls. I have a link in my Green Wood Resource Guide for buying desiccant in volume. No need to try to collect 10,000 little packets from various product packaging.
Here’s the cool thing about desiccant. Desiccant drying beads are color-coded, and they change color when they are saturated with moisture.
And the best part about using desiccant is that it’s reusable. Just spread the moist beads out on a cookie sheet and bake them in the oven at 250° until they are dry and ready to use again.
Desiccant needs to be sealed and not exposed to air ever. If the desiccant beads are left exposed to air, they will suck up the humidity in the air until they become saturated again.
To use the desiccant beads to dry a green wood bowl, place a layer of desiccant in a sealable plastic bag and then place the green bowl inside the bag. Completely cover the bowl with desiccant until the wood bowl is not visible, then tightly seal the plastic bag.
Depending on the size, thickness, and shape of the green wood bowl, the desiccant can dry the wood in as little as 24 hours.
Check the bowl for dryness and see if the beads have changed color to indicated moisture saturation. If the beads are wet and the bowl is not entirely equalized, bake the beads until dry and do it again.
Managing Twice-Turned Green Wood Bowls
If the particular wood species you are using is prone to cracking, it is a good idea to seal the end grain immediately after turning the twice-turned rough green wood bowl. Anchorseal is a breathable sealer that allows moisture to slowly escape and it aids in preventing cracking end grain.
For the bowls I twice-turn, I seal the end grain liberally inside and out on the roughed bowls. As the wood drys, it will lose moisture more evenly from the end and unsealed side grain.
Without the Anchorseal end-grain sealing application, the green wood pours the moisture primarily out the end grain with very little escaping from the side grain. This unevenness, like unevenly turned bowl walls, causes unbalanced stress and cracking of the turned bowl.
Think of the cells and grain of the wood like drinking straws. The end grain is the open end of the straws, and moisture quickly leaves these areas unevenly and causes stress cracks.
Later, when the rough-turned bowl has dried or equalized, it can be turned a second time to the final shape and thickness. At that point, because the green wood has undergone the drying and movement process already, it will stay very close to the final turned appearance with little or no further shapeshifting.
Measuring Green Wood Bowl Dryness
So how do we know when the wood is “dry,” (a.k.a. equalized)? We need to measure and check.
When you’ve worked with a particular wood long enough, you can sense when the wood is dry and stable. However, that can be an elusive and time-consuming sense to acquire.
There are two ways to measure for dryness. A standard wood moisture meter can be used to measure the moisture content in your bowl.
The only problem with this method is it can leave small pinprick holes in the bowl surface. Also, readings taken from different areas of the bowl can reveal very different results.
I’ve found that I don’t always get a confident answer with moisture meters. However, I do use a moisture meter to determine very wet wood compared to more dry wood.
For more precision, I use the following technique to measure green wood equilibrium.
The method I find most useful for measuring the dryness of a green wood bowl turning is weighing the bowl. Yes, weighing the bowl will give you the best results because you actually measure the amount of water in the bowl.
I find weighing in grams is the easiest way to get a precise, and easily comparable weight reading each time. Use a small digital scale, like this one, which has a gram reading and weigh the bowl. On a slip of paper, write the date and the weight in grams.
Come back a few days later and repeat the process.
Here’s the cool simple conclusion to this process. When the weight stabilizes, the bowl’s moisture content has equalized for its environment.
It’s really that simple.
Equilibrium Can Go Both Ways
Believe it or not, I had a twice-turned bowl roughed out and placed in a dryer. I kinda forgot about it until one day I decided to pull it out and turn it for the final finished shape. Everything was fine with the wood, no cracks formed and it turned very well.
With the piece complete, I decided to weigh the bowl to measure how much moisture was still inside. As the days went by and I noted the progress, I was quite surprised. This bowl was not losing weight, but instead GAINING weight.
What had happened?
Well, in the time I forgot the roughed bowl in the dryer, the green wood went past the point of equilibrium, and the wood cells held less moisture than the relative surrounding air humidity.
When the bowl was removed from the dryer and returned to the relatively moist air it began absorbing that moisture and gained weight, just like a dry kitchen sponge soaking up water.
The moisture weight gain was minimal and did not change the bowl shape or structure enough to notice, but it was a great example of how the wood is never truly dry and always evolving.
I hope this article gives you new ideas for how to work with green wood. There are many advantages to working with green wood, but most importantly, remember to experiment.
With all the possible variables it’s impossible to know precisely what will work and what will not. Without committing too much time, simply turn a few pieces and try drying them a couple different ways.
Take notes about your drying processes so you can recall what works. Once you’ve discovered a process for a particular species of wood, forge ahead and start creating beautiful green wood turned bowls with your new knowledge!
Drying Green Wood Bowls Conclusion
Green wood is fantastic to turn, low on flying dust, easy on tools, and usually very affordable, as in FREE. Awareness of the changes that take place once the green wood is turned is the key.
It is important to realize a transformation is taking place from a living structure to a more static artistic form. The transition between these states must be acknowledged and respected.
With a bit of experimenting and knowledge about how wet green wood dries, or equalizes to the surrounding ambient conditions, we can more reliably make fantastic green wood bowls.
While it might seem a bit frustrating, while striving for the best looking bowls possible, cracks and mishaps are going to happen. Learn from them. Remember what works and what doesn’t work, then play and have a blast turning and drying green wood bowls over and over.
Here are other green wood articles to consider:
• TWICE TURNING WOOD BOWLS – HOW TO STEP BY STEP
• BANDSAW BASICS FOR WOOD BOWL TURNERS
• GREEN WOOD BOWL BLANK MAKING PROCESS
• BOWL TURNING GRAIN ORIENTATION – WOOD BLANK DIRECTION