Tree Burl Breakdown

- Hi, Sanford Smith here with Penn State Extension.

Today's video is about tree burls.

Tree burls are a specialty wood product, sort of like spotted wood or curly maple, and lots of people enjoy looking at them, and they're used to make interesting and useful things.

And I'm joined by Keith Smalley today.

He's a volunteer with the Pennsylvania Forest Stewards program who helps fellow landowners manage their property.

Keith, what can you tell us about tree burls?

- My understanding of tree burls is they are caused by something getting into the tree.

That could be a viral infection, that could be a fungal infection, or that could be an insect.

Something gets into the tree and invades the tree, and the tree is creating a tumor, or to put it in people terms, a tumor to try to isolate that infection.

This is a three-sided part of a tree that includes a burl in the tree.

This would be the center of the tree or the heart of the tree.

Out here would be the external where the bark is, and the growing part of the tree.

So this tree was infected by whatever caused this burl at this point in its life, and then continued to grow, creating a tumor around that infection to keep it from spreading to the rest of the tree.

But if it doesn't kill the tree, then the burl keeps growing, just like the tree keeps growing.

The tumor gets bigger and bigger as the tree gets older and older.

Foresters search older forest stands for burls that have been growing for many years.

As the tree matures, so do the burls.

Just like the trees, the burls can reach a point of being overmature, and start to decay.

It is important to harvest them, before they reach this stage.

Once they locate a burl that meets their requirements, they cut down the whole tree and cut away the trunk from the burl.

During this process, they ensure their cut is in the trunk of the tree, being careful not to lose any of the burl.

The density of the wood in the burl, is much greater than the density of the wood in the trunk itself.

It is important to plan how you will get this very heavy product out of the woods.

Upon arrival at the shop, unwanted material is removed around the burl.

This removal of material speeds up the drying process that has to take place, before the burl can be further refined.

The drying process will take up to one and a half years, depending on the size of the burl.

Attachment devices are used to mount the burl to the turning lathe.

The operator will rotate the burl by hand to ensure that it does not contact the tool rest, before starting the machine.

The operator is very cautious when he cuts near the center of the rotating burl, that is the most dangerous point of this operation due to the changing direction of the rotation.

The speed that the burl turns on the machine is dictated by the weight balance, which affects vibration.

The operator stops the rotation many times, during the machining process to inspect the progress, and to locate unwanted defects.

Although the operator has a basic shape he is trying to achieve in the beginning, that plan changes often during the machining process, based on what he sees during these inspections.

The operator changes knives to create beads, and also to refine the cut, and smooth the surface.

The surface is further smoothed by use of sandpaper.

The final operation is to apply a high-quality semi-gloss polyurethane to enhance and protect the burl bowl from contact with other objects and rapid moisture gain or loss.

- Wow, that was quite a tour of that woodworking facility, Keith.

All the work that's going on there to produce a bowl from a burl, that took about three hours, it's really quite a process.

You know, burls are used to make many other kinds of products, and many different species of trees have burls.

So it's really interesting how burls can be used to make tabletops or candlestick holders or pitchers or bread dishes, all kinds of things, plates and things.

And you can see in these pictures all the beautiful objects that can be made by burls, and there are many more.

I wanna thank you, Keith, for helping make this video, and the whole process we went through.

It's been a lot of fun doing this with you.

And thank you for joining me.

- Thank you for including me in the process.

- Yeah, and thank you, folks, for listening.