Van Dyck Crystals are a traditional and natural water-based wood dye made from walnut husks. They produce a colour ranging from a very light brown to dark brown depending upon the concentration, and are the traditional method used for colouring oak, mahogany and walnut. The intensity of colour produced is controlled by the strength of the dilution.
Dissolve the Van Dyck Crystals in hot water (about 100g to 1L). Test the colour on a spare piece of wood, and darken by adding more crystals or lighten by adding more water. To obtain different shades Concentrated Water Based Dyes can also be added to the solution.