The Wedgwood Museum

The production of jasper, the triumphal outcome of about 5,000 meticulously-recorded trials over a period of some three years, was Wedgwood's most important contribution to ceramic art. Josiah wrote in his commonplace book regularly, noting the results of trials, and ideas often accompanied by illustrations. He wrote to his partner Bentley in March 1774:"I have for some time past been reviewing my experiments, & find such Roots, such Seeds as would open, & branch out wonderfully if I could nail my self down to the cultivation of them for a year or two."

The composition of jasper was a closely-guarded secret and when Bentley asked for the formula, in February 1776, Josiah carefully sent him half the details, with the remainder of the information three days later in a separate letter.

Industrial espionage was a very real and constant worry to the principal manufacturers. When the La Rochefoucauld bothers toured the industrial heartlands of England in 1785 they were welcomed by Josiah's agent but when they asked to see the black basalt production, they were firmly forbidden entry: "We…were no further forward than we had been in London where their principal warehouse is."

It was vital to Josiah that he should protect his industrial secrets as it could otherwise could mean the loss of several years lead over their foreign rivals. Spies were a constant menace and the potters were always on their guard against them. But what they feared even more than the spies was the emigration of their workmen who were enticed away by the agents of rivals abroad.