Warping Dry Bowls

Over the past few months I’ve been spending quite a bit of time on the lathe experimenting and making a pretty large variety of plates, bowls, and trays. I got my first lathe back in 2009, and while I’ve never been solely focused on lathe work, I still think woodturning is fascinating. It’s such a different form of woodworking from furniture making and carpentry where most of the time your’re working with flat square cuts and surfaces. Turning is so much more freeform and sculptural, and while there are certainly still limits, it opens up a whole new world of design possibilities.

Recently, I turned a small dish from some scrap cherry and decided to test out how thin I could turn it. I finished the piece on the lathe with the edge tapering down to about 0.5 mm (about 1/64″). After taking it off the lathe I then brushed on some iron acetate (steel wool/vinegar) to see what effect that would have on the color of the piece, and an unexpected thing happened. When the iron solution soaked into the grain along the thin edge, the edge began to buckle and ripple as the grain soaked up the liquid and expanded. The effect was pretty subtle and isolated to just one area, but it was cool and unexpected result.

I’ve always been fascinated by the effect of green wood warping and distorting in unique ways when turned thin (some really great examples are the work of Ernst Gamperl), but I don’t have great access to green wood at the moment. So the suprise rippling on this little dish got me thinking about how I could intentionally introduce some shape into pieces turned from dry wood, and I’ve been exploring different techiniques and materials to see what gave me the best results.

Initially I started with small maple bowls, testing out a variety of shapes and rim thicknesses. Some of these bowls I left natural, and others I coated with iron acetate turning them grey.

I’ve found maple to respond really well. It warps easily and I’ve yet to have any issues with maple splitting. In fact with the method I’m currently using to warp these vessels, I’ve only had a small cracks develop in 3 out of the 50 or so pieces I’ve made so far, and that was in birch and beech. The more difficult aspect to making these warped vessels is that i have to turn them really thin, which has pushed me to get much better at turning in general. In some ways thin turning is a lot like trying to plane wood as thin as possible (kezurou-kai); it really pushes you to develop good sharpening technique and tool control.

Below is another maple bowl, this time about 150mm diameter (approx. 6″) which shows just how wild the level of warp can get on maple when it’s turned thin.

Aside from maple I’ve also been experimenting with cherry. Below is a fairly large cherry bowl (270mm diameter/ 10.5 in.) before warping. The rim is about 2mm or 1/16″ thick.

And here’s the piece after warping the rim.

And here is the same piece after treating it with iron acetate and finishing it with Hassui Ceramic. Just like when you steam bend wood, there is definitely some “spring back” with these bowls. The wood definitely has a tendency to return to it’s original state to a certain extent, and the level of warp will settle down a bit over the course of a few days.

Below are some of the other cherry bowls and cups that I turned and warped. There’s one natural piece in the bunch, and the rest have been treated with iron acetate.

One of my favorite pieces from the above batch of turnings is this cherry bowl. I took the rim on this piece down to about 1 mm thick, and after warping it really developed a nice undulating rim.

The latest batch of pieces I’ve been working on are some birch bowls from a chunk of wood a friend gave me. My experience working with birch is pretty limited but so far it seems to turn beautifully and really responds well to my warping process.

So that’s what I’m having fun with these days. A bit of a departure from some of my other projects, but it all bleeds together in the end. When it comes to woodworking there’s nothing more enjoyable to me than spending time in the shop experimenting, testing out new techniques, and exploring different approaches to work.

Thanks for reading.