It's been a real pleasure of a job to do. The hardest part was matching the colour of the seats to the old, dark cane of the backs.
Chair cane is, of course, VERY glossy and hard on the front, and most wood treatments just tend to slide off, or, worse still, come off on people's clothes, so one has to be careful. When it does stay put, it tends to be very transparent and pale. But I think I've finally found the solution.
I'd never tried water-based varnish on cane before, and didn't think it would stick, so I did numerous experiments with offcuts of ready-woven cane until I found the perfect combination. In the end I used a couple of layers of dark, spirit-based woodstain, plus, on top, another couple of layers of water-based, medium brown, gloss varnish. It's a good colour, and a nice looking finish. The customer was delighted!
Having the same number back and front makes a much cleaner looking pattern. You hardly notice the slight distortion as the verticals splay out towards the front. I think it's a much more sensible solution, and if I were making my own chairs from scratch, I'd definitely do this.