St Eilian Colour Works manufactured colours and paints from the by-products of the process of recovering copper from the waters drained from the copper mines of Parys Mountain. Water rich in iron sulphate was allowed to evaporate to produce hydrated iron oxide or yellow ochre, which was then crushed by edge runners driven by the windmill.
The works was in operation before 1850, but had been demolished by the time of the 3rd edition of the 25-inch O.S. map (1920). Edge runner stones found on site were 0.66 metres in diameter.
W J Crompton, RCAHMW, 1 October 2008.