Turning a Madrone Burl Bowl - Part 2

Roughing out the interior of the bowl blank on the outboard side of the lathe to create walls ofthe desired thickness.

Once I have cored out the interior, I use the 5/8" deep bowl gouge to turn the walls to the desired thickness (approximately 1" thick for smaller bowls). However, on bowls over 14" in diameter, I will go about 1 3/8" to 1 ½" in thickness (see Fig.3).

Double-ended calipers are a must. If the wall thickness gets too thin at this stage, the bowl may dry too far out of round, thus eliminating any chance that the remounted bowl will be able to be re-trued. If left too thick, it will most likely crack as it dries.

Different species of wood will dry differently. In addition, the location where the blank was cut out of the tree will also affect the way it dries: a rough-turned, quartersawn bowl will dry differently than one turned from a flatsawn blank, and a wet burl blank can and will move in any direction.

Boiling Process
At the end of the day, I take all my roughed-out bowls and put them in my boiling tank. Stainless steel must be used for the tank because iron might react with the tannins in the madrone and will, most likely, discolor the wood to an ugly, dirty, blue/black color.

This is the tank I use for boiling the roughed-out blanks.

When I first started to experiment with the boiling process, I was only making a few bowls. I used my mom’s pressure cooker to boil one or two blanks at a time. Now, I use a 2’ x 2’ x 3’ stainless steel box that someone made for me from scrap metal (see Fig. 4).

I cover the bowls with water, use the scraps from the roughing-out process to create a fire, and heat the water to boiling. I like to boil the bowl blanks for a minimum of two hours. After that, I simply quit adding wood to the fire and allow the water AND the wood to cool until morning.

I have discovered that the bowls must remain in the water until its temperature cools enough to allow me to reach in by hand to retrieve the blanks. If the bowl is removed while it is still hot, any water remaining within the wood simply boils away and causes the blank to crack.

I also use the boiler when I am turning our local fruit woods like cherry and apple. Both of these woods (especially the sap wood portion) are very difficult to dry without cracking. The boiling technique has allowed me to successfully turn these woods. I usually don’t boil any nut woods like walnut, oak, or maple; however, I simply rough turn them and then allow them to air dry.

After I take the bowls out of the water, I date the bottom of each bowl and note where I got the wood. This enables me to track all the bowls throughout the entire drying process.

Drying the Blanks
Many people ask me, "How long does it take for the blanks to dry?" I usually answer that it depends on several factors: where you live, the species of wood used, and the time of the year. For me, madrone burl will generally dry in six to eight months. Other woods, (white oak, which I don’t boil, for example) may take up to two years. The question then (more properly) becomes one of "How do I dry the bowls where I live?"

There are two simple guidelines that I use to successfully dry wood:
1. If the blank dries too fast it will crack. If the blank starts to crack, you must deal with it immediately when the cracks are still very small. I use thin cyanoacrylate glue (CA or super glue) to fill the cracks. Then I put that blank into a plastic garbage bag along with some dry wood chips. This will allow the moisture content between the dryer exterior and the still damp interior to equalize. The dry chips will soak up any excess moisture. Once the wood has the same moisture content, it will not crack any further. Keep in mind that bowls prone to cracking might have to go in and out of the bag several times until they are dry.

Go to: Turning a Madrone Burl Bowl - Part 3