In August 1914 Great Britain declared war on the German Empire and by 22 October the production of clay had ceased. Although the war had halted production the inconvenience was not expected to last long but as the war continued into a second year several china clay companies in Devon and Cornwall either closed down or greatly reduced their production. The scarcity of labour, the increased price of coal and a depressed market all added to the uncertainty although Redlake was able to resume operations in a small way by September 1915.
In October the colour and quality of the clay resulted in a contractor refusing to take delivery of an order for the whole output of the pit. In fact, two grades of clay had been found; one of good quality from veins running NNW to SSE and one ‘of yellowish colour only suitable for producing bricks’, present in much greater quantities surrounding the better clay.
The poorer clay carried appreciable amounts of tin oxide and a small amount of tin was produced between 1915 and 1919 with a stamping house costing £300 erected at Cantrell in March 1916.
The better clay itself proved not to be of the highest quality, with a poor colour and, because of its high iron content, too abrasive for use in the manufacture of paper. Its main use was in the manufacture of pottery but its poor colour when fired made it useless for porcelain.
In the autumn of 1915 there were 50 men employed at Redlake. In 1916 over a quarter of a million tons of clay and sand were removed and the double track ‘sky’ tip was constructed at Redlake. Production continued on a small scale but by 1917 only a quarter of the number of workmen were employed compared to when the War broke out – mostly older men and boys, although there were also some women doing relatively light tasks at Cantrell and Redlake.