For darkening cement to be used for pointing brickwork bricklayers use smithy ashes, which can be procured from any blacksmith. The ashes should be ground or crushed to the size of sand (not crushed to powder) and used instead of sand, or sometimes a small quantity of sand is mixed with the cement and cinders. The wearing qualities of the cement are not improved by the use of cinders. Lampblack is occasionally used as a colouring agent, and when it is used sparingly the wearing qualities of the cement are not lessened.