In this workshop I paint the background around the dragonfly with 'milk paints'. These are a very old, non-toxic, type of paint, more and more available with a search online. Here's a link to Wikipedia all about them.
Milk Paints come in mixable, powdered form to which you add water. Why did I use milk paints? As you'll see, you can build up layers and then polish back with 0000 wire wool; the result is a ceramic-like look that is so much better in this context than any other painted finish. And it's the tiled-look we want for this Arts & Crafts project. Do experiment first before committing your colour to the carving!
This works on Oak and Walnut. First make up your witches brew:
The iron reacts with the acetic acid in the vinegar to produce iron acetate. This in turn reacts with the natural tannins in the Oak to give you the black colour. And that's as far as my chemistry goes!
I used 'Process Black' in the numbers, though I'm sure most any other black will do. Acrylics are fast drying and don't wick into the pores of the wood at the edges on the letters or numbers as will, say, slow-drying, thinner oil paints . You can further inhibit wicking by sealing the insides on the numbers with a PVA (wood) glue before painting.