In 1844 he developed a process for treating cotton, mercerisation, that improves many of its qualities for use in fabrics. John Mercer never went to school, he learned basic reading and writing from his neighbour. He was very fond of dyeing.
With the help of a chemistry textbook he taught himself the basics of the dyeing process.
He continued to experiment, until he discovered Antimony orange. Later on he developed the mercerisation process and was admitted to the Royal Society, the Philosophical Society and the Chemical Society.
(Florence Nightingale was next door, at Number 30). Mercer died at home in 1866 and was buried in Street Bartholemew"s church.
Mercer"s cottage at Oakenshaw was donated to be a museum and park.