Shell gold, so named as it used to be made and stored within shallow seashells such as clamshells, is genuine gold powder finely ground to a pigment and bound with gum Arabic to form a solid watercolour block. Shell gold is used just like watercolour pans, by first wetting the block with water to release the paint and then applying it with a soft-hair brush. When painting with shell gold you can add a drop of Ox Gall to break the surface tension to improve the flow of the paint.
When dry it gives a finely grained matte finish that can be brightened up by burnishing the dry paint with an agate- or metal-headed burnishing tool in order to produce a vibrant golden shine.