Andrew Potocnik shows how to get the most out of 'in the round' branch timbers.
Travelling home I spotted ‘bitesized’ pieces of wood neatly stacked on a nature strip and immediately recognised the bright green coloured wood as mulberry. Coming to a rapid halt, the boot was opened and the timber loaded. I’ve enjoyed using mulberry
over the years because of its vibrant green colour, streaks of black and unusual mini-burl-like growths.
The best thing this time was that it was free, and as it was green (freshly cut) I knew the wood would distort rapidly once turned—a chance to let nature have its own way. The rather thin limb sec-tions could be well exploited as endgrain turnings, making use of stable mature wood, very wet juvenile wood that might well distort while drying, a very thick cambium layer and bark that would most likely distort beyond control as it dried. So here’s where the fun starts.
Half or round section
Most people that turn bowls from green wood lay the log on its side and cut it in half to reduce splitting, an inevitable part of the shrinkage process that happens as the wood dries if the log is left ‘in the round’. I described this more conventional method of turning green naturaledged bowls in AWR#70. Many people who have trees cut down are keen to have the cross-cut trunk section converted into tabletops, stools or bowls with little understanding of how wood moves, distorts and most often cracks as it dries. Be warned: turning endgrain into the round takes either experience, or willingness to accept occasional failure.
Mounting the blanks
To begin with, there’s little to think about in terms of how to cut your wood to get the most out of each piece. Simply mountit between centres as close to the centre of each end if you want the opening to be symmetrical. If not, mount slightly closer to one edge for an interesting result. I went with the first option
trimming the timber down to a tapered form before cutting a step at the base with a parting tool
and refining the overall shape.
Normally I would sand the outside at this stage but as the wood was very wet, I bypassed this stage and mounted the bowl in a scroll chuck instead.
With the tailstock supporting the wood I began to hollow the centre with a gouge
and then a Kelton scraper, keeping a stub in the middle so the tailstock could be kept in place to add support to the bowl. Once the bulk of material was removed, so was the centre stub, allowing finishing cuts to take place along the wall of the bowl before the base was refined with the curved scrapers. I supported the outside of the bowl with the fingers of my left hand whilst completing finishing cuts in order to reduce vibration and possible catches.
Once satisfied with the thickness of the walls I began sanding the bowl,
but as the wood was still very wet I dried the surfaces, gently warming them with a heat gun. Once sanded to 320 grit I reversed the bowl onto a domed carrier, first placing a non-slip mat over the carrier.
The mat pads the carrier so it won’t damage your wood and prevents the bowl from slipping while you’re turning. I held it in the scroll chuck and supported the base with the tailstock. The spigot at the base was turned down to a small stub, and the base sanded before the stub was removed with a small carving gouge and also sanded.
You can see some cracking at the centre of the limb section.
To reduce cracks developing or at least preventing them from becoming unacceptably large, it’s a good idea to keep the finished article as thin as practical, this way the form may distort and possibly even close the crack as it dries. Various species will behave in different ways so it’s best to experiment and see what works, otherwise look at ways of making the crack a feature as I have done on some pieces by burning their edges or just filling the cracks. I have used epoxy resin for this, but French turner Christophe Nancey has at times filled cracks with pewter.
As you can see, getting the most out of small pieces of wood can be fruitful, and at times risky, but it’s always nice to know you’ve been able to salvage timber that may not have been of a usable size and
converted it into a finished item. And then you can watch what happens as nature takes over as the wood dries.
Andrew Potocnik is a woodwork teacher and woodturner.