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.
When I first started to experiment with the boiling process, I was only making a few bowls. I used my moms 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 dont 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
There are two simple guidelines that I use to successfully dry