As someone with a long time obsession with pencil crayons ( I own a bin full--and yet there is always a new colour beckoning me in the art store), I was captivated by the jewelry on the cover of the most recent Metalsmith magazine. It shows a beautiful piece by Helen Shirk using enamel paint to add colour. Inside were many more of her pieces employing pencil crayons.
It seems that the basic technique involves first preparing a suitably rough surface for the pencil crayons to adhere to. This can be achieved by sandblasting, hammering metal over a rough surface (sandpaper, cement…), applying a thin coat of gesso, using the rolling mill, or adding a patina first.
The next step involves the slow and long process of adding layers of colours--fixing the piece occasionally with a workable fixative.
And finally, sealing the piece with a durable matt or gloss fixative.
Sounds fun to me!