Dartford in the well-watered, sheltered valleys of the Darent and Cray invited occupation, certainly by the Romans and successive invaders. Over the centuries trades emerged and prospered. One of particular note was the making of paper from rags. John Spilman was granted a monopoly for the collection of rags for paper making. A number of paper mills followed including the Phoenix Mill of TH Saunders noted for the quality of its early machine made paper.
Armament production came to Dartford in the mid eighteenth century in the shape of a gun powder factory. This was succeeded by Vickers, Son and Maxim in the nineteenth century in Powder Mill Lane with an ammunition factory.
In 1889, Burroughs Wellcome took over a former mill for pharmaceutical manufacture and in 1914 built a new factory which was added to over the years reaching some 65 acres and over a million square feet of building. They had 2,800 employees in 1979.
A significant if lesser known manufacturer was John Hall a blacksmith who arrived in Dartford in 1785. By the time of his death in 1836 he had a iron works in Dartford, a gunpowder works in Faversham, a paper mill in Horton Kirby and a flour mill at Chislehurst. One of his apprentices was Bryan Donkin who with Hall built a works in Bermondsey to make tin cans for preserving food. I wrote of this in How Britain Shaped the Manufacturing World. The Hall iron works supplied many local industries: gas works, zinc mills, paper mills and cement works. Of greatest importance was their work on refrigeration. It was said that in the Second World War 37% of the nations storage capacity was cooled by Hall's machines.
In 1886 Halls had installed their first cold air cooling machine on a large cargo ship carrying perishable foodstuffs. At that time Britain was the world's leading importer of food from Australia, South America and elsewhere and so refrigeration was essential. Cold air was better than previous methods but a better solution was needed. In 1889 Halls added carbon dioxide in a two stage compressor. To achieve yet colder temperatures, Ammonia was used and a plant was installed in Grimsby to make ice for the trawler fleet. In 1959, the company merged with Thermotank of Glasgow which made patented cooling and ventilation devices. The merged company bought Vent-Axia of Crawley in 1959 and was itself bought by APV in 1976. It is now part of the Japanese Daikin Group and continues to manufacture in Dartford.
The south bank of the Thames with its reserves of chalk and mud turned out to be the ideal location for cement manufacture.
Lime had been used for millennia in the making of mortar to join stone and brick. The Romans built lime kilns to burn limestone and produce quicklime. Such kilns were to be found across Britain where limestone was to hand. In the seventeenth century it was found that quicklime spread on fields would aid the growth of crops by reducing the acidity of the soil. The demand for quicklime kept growing.
There is evidence that as early as 8,000 BC it had been found that the addition of small amounts of volcanic ash gave the lime the capacity to set under water. In England, John Smeaton, known as the father of civil engineering, building the Eddystone lighthouse discovered that the property of hardening whilst submerged in water was linked to the clay content of the cement. In 1824, a Leeds stonemason, Joseph Aspdin, took this a stage further and invented a method of making from limestone and clay a cement which he called Portland Cement given the similarity in colour between it and Portland stone. He patented his invention and his son William exploited it further setting up a manufacturing plant in Rotherhithe. Other plants followed along the banks of the Thames and Medway using local deposits of chalk and clay taken from the mud of the river banks.
It seems likely that Portland cement was used by Marc Brunel in the construction of the Thames Tunnel in 1828. The story is that Brunel had been using the cheaper Roman Cement patented by James Parker of Northfleet in 1796, but the tunnel collapsed. Tons of Portland Cement were poured in and sealed the tunnel which could then be completed.
Limestone was also used as a flux for the smelting of iron to remove the impurity of silica, which when heated combines with the lime to form slag which is then removed and used for road making.
The exact proportion of lime to clay was crucial and depended on the make up of the local deposits used. The mixing would be either using water or by grinding the dry rocks. In time, cement plants appeared across Britain exploiting local mineral deposits and the availability of coal to heat the mixture until it calcined. In 1845, Isaac Johnson, then manager of the Swanscombe Works close to Dartford, fired the mixture to a higher temperature (1400-1450C) until the mixture clinkered. This was then ground to a fine powder and is essentially the Portland cement we use today.
Cement making was a dirty process and the towns folk complained. Johnson though went ahead with larger works at Greenhithe. In time there were some thousand kilns along the banks of the Thames and Medway.
In 1900 the Associated Cement Manufacturers Company was formed bringing together some twenty four companies all but two on the Thames and Medway including two of the early plants Robin's and Swanscombe. This company became Blue Circle Cement and is now owned by the French Lafarge.
Further reading:
- Geoff Porteus, The Book of Dartford (Buckingham: Barracuda Books 1979)
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