3kg Charcoal Instarmac Ultra Tile Fix Grout. Charcoal grout is an excellent choice for when you are using stronger colours when grey would be too pale but you don't want the intensity of black grout. The grout is supplied in powder form. Mix 3.25 parts powder with 1 part water and mix until a smooth consistency is achieved, leave to stand for 2 minutes then remix. Do not mix more than can be used in a 30-45 minute period, do not re-wet or add too much water.