First, let’s look at exactly what is greenwood. For many the term refers to wood that has recently been felled, however, that’s not quite right. It really refers to the level of moisture that the wood holds. For example, a tree that has been felled and left lying around can maintain its moisture level for several years. Whilst a wood shaving left in the sun will dry out very quickly.
Why is this important?
Greenwood is a lot softer than seasoned wood. This makes turning wood a lot easier and is gentler on hand tools. For example, it is possible to turn green wood oak bowls using a foot-operated pole-lathe. Once the wood is seasoned and dries out oak is too hard to work in the same way.
One characteristic of green wood is that when it dries it will change shape or warp. This character can be used to the woodworker’s benefit, for instance, when making greenwood furniture, parts are normally joined using a mortice and tenon joint. When the wood dries the tenon becomes an oval shape, by aligning the grain correctly the distortion locks the tenon in place forming an extremely strong joint without the use of glue. In my case, as a bowl turner, when I prepare a log to be turned into a bowl I split the wood through the centre of the log. This releases much of the tension that causes the cracks you can see in the following picture.
I turn bowls on a traditional pole-lathe. You can see examples of my bowls in my shop.
This makes using green wood vital as seasoned wood is simply too hard and would blunt my tools very quickly. I also need to split the log through the centre or pith. This releases tension that would build up as the wood dries. If I didn’t, ultimately the bowl would split.
As the bowl dries it will naturally warp. This gives every bowl I make its own unique character. There is still the risk that the bowl will crack during the drying process which can be frustrating, however, it can also lead to some interesting results like this bowl which has been repaired using butterfly ties.
As you can see the pith, or centre of the log, is very close to the top edge. As the bowl dried it created a lot of tension that has resulted in serval cracks appearing. To stop the cracks from getting any larger the craftsperson has used butterfly ties. Other makers use copper wire or staples to perform the same task.
Whilst fixing the bowl is an interesting project and can end up with a unique item, the aim is to create a bowl that is durable and long-lasting.