The Vanishing Witch Page 54
This was highly unpleasant work as the ammonia fumes from the stale urine could cause the walkers to pass out and drown in the vat. The fumes also caused long-term respiratory and eye damage, and fullers could catch nasty infections. So by this period in the Middle Ages, fuller’s earth (a soft clay) was beginning to replace urine in the cloth trade. But it was mainly found in the southern counties of England and had to be dug out, baked in the sun, formed into a powder and transported. So, particularly in the north, it was far more expensive than using local urine, and many cloth-makers were reluctant to switch to it, as long as there were fullers desperate enough for employment to scour and mill the cloth in the old way.