A self-preparation of two parts trass cement and one part fine quartz sand is often recommended for grouting cement tiles. This procedure is to ensure that there are no colour pigments in the grouting compound as in many industrially produced grouts. Cement tiles are hydraulically pressed during production.
Due to the lack of a burning process, they have a more or less finely porous surface. The use of pigmented grouts eventually leads to an accumulation of colour pigments in the open pores and thus to discolouration. Such colour particle accumulations are particularly noticeable when tile and grout colour are contrasting.