I have written about green turning several times in the past, including this post on a large green turning project with Cedar. However, as this is such an important turning technique, I thought I would start over again.
When freshly cut, all wood contains varying degrees of water content. Turning very fresh wood can result in a drenching of the turner as the water sprays out as the lathe rotates. In most cases that I am familiar with, the wood has dried a bit, but unless the wood was kiln dried, or waxed or otherwise preserved and you have waited sufficient time for it to slowly dry, you should assume it is wet to some degree.
Wet or green wood is very easy to turn. Green wood cuts faster and in very long strips compared to the slower going with a dry wood that tends to produce a lot of dust. But once the wood is cut, either breaking the bark or breaking the wax or other preservative seal, water will start to migrate out of the wood. Water can move out of wood very quickly and environmental factors will influence this. In a cold climate water will move more slowly but in the heat of summer it can move fast. The water will mostly move out along the end grain and if the water flows faster than the wood can expand the result will be cracks, called checks. Bad checking can ruin an otherwise great turning blank, so green turning techniques help to slow that.
A green wood blank is turned the same as any other blank but you are aiming to leave behind at least 10% of the material for final cutting. So, in a 10″ blank, you would leave the walls at at least one inch thickness. I use my regular Easy Wood Tools for the turning process and held the blanks in the my standard Nova Chucks. Because the wood is green your tools and lathe can end up wet. My Robust American Beauty lathe has stainless steel beds that won’t rust when using green wood, by design, but not all lathes have this feature. If your lathe bed is not rust proof, dry it thoroughly. Do this other tools you may use in the green turning process, including bandsaw and turning tools. To facilitate drying, I took the cutters off all Easy Wood Tools to prevent rusting of the set screws. If you are doing a lot of green turning, coat the screws in beeswax, available at any woodworking store, before assembly.
Once the rough bowl is finished, it must be preserved. There are many ways to do this. Plain latex paint will work, shellac works, wax works, diluted white or wood glue works, or you can use any of several commercial products designed for the purpose of slowing the drying of green wood. Anchor Seal is probably the best known of these, bit I used a product sold as Tree Saver Green Wood Sealer, marketed by Craft Supply USA, which as it turns out, is really just a gallon of white Elmer’s type glue that was dyed green. Live and learn. A gallon of glue costs a great deal less than the advertised product.
Regardless of what you use, the blank must be thoroughly coated and sealed. You could risk just sealing the end grain as that is where more water loss with occur, but I coat the entire piece to be as safe as possible.
As you might imagine, this gets to be a somewhat involved and messy process. The way I handle that is to batch green blanks, in this case five blanks, all turned at once and then coated and stored. In this way, the effort is less burdensome than doing one blank at a time.