Underglaze colours are applied direct to the biscuit ware, and are therefore under the glaze that is applied after colouring. The coloured ware should be heated to the same temperature as in burning for biscuit, but the different colours may require different times, which will be found by experience. Time is not very important, however, as the colours are, to a large extent, fixed by a short heating, because they usually contain fusible materials.