Clinker manufacture operational: 1874-1915?
Approximate total clinker production: 196,000 tonnes
The plant is shown on the 1899 and 1913 County maps. Davis assigned it an output of 250 tons per week in 1907. There was also a plant known as Ysceifiog about 2.5 km east at Sarn Mill, mentioned by Francis, but this was extinct before 1895. A paper mill previously occupied the site, and water power was originally used. This seems to have been the first plant to attempt to make real Portland cement from Carboniferous Limestone, although the plant (and the paper industry) were probably originally predicated on the use of the "tufa". There is a local placer deposit of chalky consistency produced by downwash from the high-grade limestone of Ffrith-y-garreg-wen, 4 km to the north. The high-purity limestone was dry-ground, then washed with clay to a thick slurry. Henry Reid described its operations with some amusement: the stone was inadequately ground and led to high free-lime levels. The plant had three wet process bottle kilns until 1900, after which seven chamber kilns were installed. A further three had been installed by 1907, to give total capacity 250 t/week, but its rating was only 200 t/week in 1913, with a fuel consumption of 15.7 MJ/kg. It was derelict in 1924. It was close (300 m) to Caerwys station on the Mold & Denbigh Junction Railway, which was its main transport link. The site is now a holiday park. The Johnson kiln bank still stands: the chambers have been built over, but the hot end remains in good condition and is a Grade II listed building.
No rotary kilns were installed.