We finally chose a red silk dupioni that matches the final tone of the rose panel. There is a layer of thin canvas underneath (I tried extra heavy duck first but this was too bulky).
The rose panel was discolored, so I removed the mattine varnish (shellac + wax) and wax I had put on it, refilled the crack again, re-dyed the panel with aniline (it seems the places where there was aniline were more lightfast than the “mahogany” dye, go figure) to a deep red, and this time very lightly waxed it.
The rest of the chair is just waxed with medium oak tone wax, which is a little reddish. I thought they were chestnut, but now I am fairly sure the chairs are oak.
I still have another chair to restore, although that one is functional (the one I restored first was a mess, all wiggly, someone stabbed it with screws in several places, splintered, the carved panel split… ). So who knows when I will gather the courage to start all over ;P
So a before and after of sorts:
And a detail of the fix and the bottom that nobody is ever gonna look at again: