Sessional_Paper_1929 — Page 77

70

(b) Red Clay.

This clay, owing to its colour, is not adapted for many of the purposes to which a white clay can be applied.

The results of the experiments carried out indicate that good second-grade pottery of a light terra cotta colour can be produced from mixtures of the finely-ground clay with ball clay, and that by increasing the firing temperature, dark brown impermeable ware can be made.

If it were found necessary, the composition of the body could be varied by the addition of materials, such as flint, Cornish stone, or felspar, but as a satisfactory earthenware was made by the addition of ball clay alone, it was not considered necessary, at this stage, to carry out more extensive experiments.

(a) and (b).

The white and red clays, generally speaking, cannot be regarded as high-quality raw materials. The white clay yields on washing a material resembling kaolin, from which sound earthenware can be made, and lower-grade ware can be produced from the red clay, but the difficulties of working were such that economic manufacture on a commercial scale might be impracticable, and it would be necessary for preliminary large- scale tests to be carried out.

15th May, 1929.