At the end of the nineteenth century most of more easily mined tin ore deposits had been exhausted. This in conjunction with the emerging foreign opencast mining, reduced the price of tin put the Cornish mining industry under dire financial pressure.

A by-product of tin smelting, arsenic, came to its aid. Arsenic was being increasingly used in manufacturing. This was particularly so during World War I, when it was employed by the military, increasing ten fold in price.

Prior to the importance of arsenic, the toxic arsenic fumes were just fed into the air. To collect the arsenic, the smelting houses had their toxic fumes drawn up through calciners.

Arsenic condensed on the calciner walls. The arsenic could then be scraped off the walls, not a healthy job.