The Mynydd Parys copper mines resulted in numerous other factories and industries being established locally and nationally.

Thomas Williams built up a significant business empire that included, mining, smelting, transport, manufacturing, export and banking.
The basis of this empire were the mines at Parys mountain. The first partnership was between William’s and Edwards Hughes the landowner of Parys farm to form the Parys Mine Company (PMC) in 1778.
Warehouses, offices, roasting kilns, lime kilns and smelters were set up on the mountain or in Amlwch Port. By 1786 there were 31 reverbatory furnaces with chimneys 41-foot-high in the area. A Sulphur extraction works based on the Champion batch process was built on the mountain. Later continuous Sulphur processes methods were used.

In around 1780 the PMC built a smelter in Ravenshead in South Lancashire. This was close to a plentiful supply of good quality coal needed in the smelting operation. A Sulphur extraction plant was also built at this smelter. The smelter contained 48 reverberatory furnaces,all the same size used for the preliminary roasting and for the later stages of smelting and refining. Charcoal was an important part of the smelting process.
It is estimated that that over 1000 tonnes of copper per year were produced. The works consumed up to 36,000 tonnes of coal per annum. The works employed between 200 and 300 men.
Some skilled workers had to be encouraged to move to the works from the established smelters in South Wales. These workers were housed in 16 specially built houses which were known as “Welsh row” In addition the manager of the works, Michael Hughes, provided newspapers and a sick club in the Navigation Tavern

At around the same time another smelting works was obtained at Upper bank in Swansea. This area also had good coal and port facilities and had been a centre for smelting activities for Cornish ores for many years.
A manufacturing facility for copper wire and plate called Holywell Mills was established near Holywell in Flint. This mill manufactured materials for the slave trade but also became very important in the process for cold rolling copper bolts and nails for copper sheathing. The process was described by Lentin. For a short period, the Parys mountain penny and other coins for Holland were manufactured here.

By 1785 Williams had also obtained control of the Mona mine. Warehouses, offices, roasting kilns, and smelters were set up on the mountain or in Amlwch Port. In addition, a new pier and quay were built at the port.
A separate company known as the Stanley Company smelted the ore from the Mona mine at works which were set up near St Helens and at middle bank in Swansea

A subsidiary company called the Greenfield Copper and Brass Company had a manufacturing base in Flintshire. This company took the copper from the Stanley works and reacted it with calamine to make brass. This was then used to make a wide variety of articles. The manufacturing techniques used are described in the section on the Brass Industry.

The Greenfield Brass and copper company works 1792
Thomas Williams also owned two other factories in the Thames Valley. These were called Temple Mills and Wraysbury Mills.
Warehouses and sales / export offices were set up in London, Liverpool and Birmingham.

After 1780 William’s spent much of his time at the London offices. His second in command here was Pascoe Grenfell. He later played a major part in the formation of new company with Thomas William’s son to buy Cornish copper ore. Thomas Williams also had control of this Cornish ore via the Cornish metal company which was operational between 1787 and 1792.

Another company called the Chester and North Wales bank, with branches in Chester, Bangor and Caernarfon was set up in 1792. Pascoe Grenfell also became involved in this venture which survived until it was taken over by Lloyds Bank at the end of the 18th century.

When Thomas Williams died in 1803 the two smelting works in Swansea were taken over by the Williams and Grenfell company. In 1814 the company also brought out the Greenfield manufacturing operation. The Ravenshead smelting works closed in 1813 and smelting was restarted at Amlwch.

A Dr Joshua Parr, set up the Mona Vitriol company on land to the East of the mountain 1803. This company initially tried to make Copperas which was used in the manufacture of inks and pigments. However, problems with the separation of Iron oxide meant that this process had to be abandoned.
Next sulphuric acid was made from the copperas extracted from the precipitation fluid. This was initially successful but later failed as the copper companies began to produce the acid direct from Sulphur.
The Parr company then tried to produce pure copper sulphate or “Blue vitriol”. This also failed and alum production was tried. The alum was used in the production of dyes and pigments and also in the leather tanning industry.

The copper precipitation processes at Mynydd Parys are described elsewhere. The final liquors from these processes where high in iron sulphate. This material was let into large pools where it was further agitated to increase the amount of absorbed oxygen. The ferrous sulphate solution eventually precipitated out and after grinding was used in paint manufacture at the St Eilian Colour Works factory in Amlwch. By increasing the time spent in the pools successively darker shades of ochre could be made.

The Garston Vitriol Works had been set up by Thomas William’s in Liverpool in 1792 to make sulphuric acid from the Sulphur that was produced at Amlwch and Ravenshead. Much of the acid was sold to the Pen Maes company who sold it on to the developing textile and pharmaceutical industry

However, towards the end of the century all the Sulphur was being used to make gunpowder. This company was sold in 1799 where it was described as consisting of ” four large warehouses, four very large lead houses for the condensation of vitriolic acid, one evaporation house, four extensive furnaces, a brimstone grinding mill together with laboratories, manager’s house and riverside loading quay”.

The connection between Mynydd Parys and sulphuric acid manufacture was re-established in 1840. In that year Mr Charles Henry Hills was attracted to Amlwch by the cheap and abundant Sulphur supplies. He located a works on the Llam carw headland which made fertiliser from the Sulphur.

By 1860 the amount of Sulphur made by the mine was declining. Hill had entered into an agreement with Evan Evans, who then run the Mona mine to calcine all their ores.In return Hills would make sulphuric acid from the Sulphur by the direct pyritic process that he had invented. A new factory for this process was built on land to the west of the port. The sulphuric acid was combined with imported phosphate rock or Guano to make fertiliser.
By 1893 almost all the smelting process at Amlwch port was carried out by Hills and company. However, after 1897 the company returned to just making fertiliser from imported materials. For many years, until it was built over as a housing estate , the area was known as “Gwaith Hills”