If you want solid back, put on a few coats of acrylic black gesso. Grainy wood needs to be filled first using fine polyfilla (or similar).
Two/three coats of gesso. Sand smooth. Then follow on with black acrylic. Again 2/3 coats. Don't go too thick - dip your brush in water
as you apply it. Brush out all the brushmarks with an unloaded brush. As it dries it should go very smooth. When that has had >4 hours or
so to dry, apply wax(I use Black Bison Tudor Oak but any dark colour is suitable). Apply with wire wool, but don't press hard. Wipe off excess.
Let it 'flash off' so all the solvent evaporates. About an hour later, take a nice soft cloth and buff it.
You can apply a coat of Red Iron Oxide acrylic under the black and the you can rub a bit harder with the wirewool to expose the underlayer
particularly on raised parts and edges.
It's quick and easy and the results are very gratifying.
Black is a quite tricky finish as every lump/bump/blemish will shout out. I often stipple the gesso or use it thick and work in random sweeping
brushmarks. It's a matter of taste, but it can give extra visual interest.
btw. I like your gilding.
![Yes :yes:](./images/smilies/emoticon-0148-yes.gif)