There are three vital commodities needed for a successful blast furnace, iron ore, wood and water, and Warren furnace operated because all three commodities were in the area. Iron ore was local and the ore for Warren furnace was quarried adjacent to the furnace. There is evidence of ore extraction pits in the Sharpthorne area dating from the Middle Ages. Wood was used to produce charcoal as fuel for the furnace. A coppice system was operated whereby small trees such as hazel were cut, in a fifteen year cycle, to produce small branches to turn into charcoal and create a coppiced woodland, allowing larger trees such as oak to grow on and be used for ship building. Among the sources of wood for Warren furnace were Cuttinglye Woods and Myllwood. To keep a furnace in blast it has been estimated that about 2500 acres of coppiced woodland would be needed, with a further 1500 acres to run a forge, in this case Woodcock Hammer. The third commodity needed was water and this was in plentiful supply after a bay or dam was built straddling Felbridge Water, creating a six acre pond. Water was required as power to operate the 4.5 metre bellows, made of oak and ox hide, that blew air into the furnace to raise the temperature, or as power for boring out guns, or, as in the case of the Woodcock Hammer forge, to power the bellows and the hammer. The period of continuous work for a blast furnace was dependent on water, and usually lasted from October to June, as the water level drops in the summer months so too does the power supply.
The area known as Furnace Wood was once known as Myllwood. It was mentioned in a lease of 1485, suggesting that a mill had been in use on the Felbridge Water, however, it is unclear whether the mill referred to was connected with the iron industry or whether it was a corn mill. The name Myllwood continued to be used well into the 18th century but by then Warren furnace was in operation and the area was also referred to as The Warren. There is evidence that a corn mill stood on the site of Warren furnace in 1780 and ran until the 1860s. This appears on the Tithe map of 1841/2 and in the Land Tax Records. It was around 1865 that the bay, of 80 metres which held a depth of water of 5 metres, collapsed. An attempt was made to repair it at the time which was unsuccessful and so the pond drained away leaving just marshy land and no water to run the mill. It was not until the 1920s that the bay was successfully repaired and the lake re-installed by the then owner, Mr. Lionel Robinson, of Furnace Lodge. Some of the work was carried out by prisoners of war that were camped in Cuttinglye Wood. The level of the pond today is much lower than when the mill was in use.
Warren furnace was in operation from 1567, when Sir Edward Gage, Lord of the manor of Hedgecourt, granted a twenty-one year lease to John Fawkner of Waldron who ran Maresfield forge and John French of Chiddingly who was in charge of the Stream furnace. Both operated ironworks owned by Sir Edward Gage.The lease states that the furnace had been erected before the drawing up of the lease. With the furnace set up it was John Thorpe, who had leased the manor of Hedgecourt, who ran the furnace. Thorpes lease of the manor specifically excluded the furnace, but a further lease, now missing, must have granted him the use of the furnace in succession to Fawkne and French. Thorpes occupation of both the manor and the furnace gave him rights over most of the land around the furnace, including Myllwood, (Furnace Wood), and Coddinglighe, (Cuttingly).
Contemporary to the building of the furnace, were several small cottages on Hedgecourt Common. Felcot and Forge Farms, now known as Felcot Farm, Yew Tree Farm and Michaelmas Farm, formerly known as Miles Farm, all probably date from the first working period of the furnace. These may have been built to house furnace workers. Each had a small plot of land on which they could eke out a living when the furnace was not in blast, the term used for continuous operation.
The blast furnace, of which Warren furnace was a 16th century example, was about 20 feet in height. It was fed at the open top with iron ore and charcoal, where the combustion was intensified by a blast of air blowing through the hot mixture, and from which, at the bottom, fluid metal was tapped. The fluid metal from the blast furnace was run into sand moulding beds in the floor of a cast house in front of the furnace to produce cast iron sows. These were about 2.5 to 3 metres long and weighed about ½ ton each. These then had to be refined as cast iron was hard and brittle, so it was re-worked in a conversion forge where it was decarbonised by re-melting and hammering to produce a loup of iron, this was then consolidated and formed into a bloom which was then re-heated and hammered several times first producing an ancony and then a bar of malleable iron for the blacksmith. There were, therefore, two separate processes, the furnace and the forge, generally in two separate locations in this instance,Warren furnace and Woodcock Hammer.
In 1574 John Thorpe, who also worked Woodcock Hammer, was warned against selling ordnance to continental buyers, of whom Spain was pre-eminent. Thorpe entered into a bond of £2000 not to export guns. In 1588, with the threat of the Armada passed, the iron masters were requested to stop casting guns. This coincided with the expiry of the first known lease, but it is not known whether the furnace continued in operation after 1588 or not, although it is most likely that the lease would have been renewed lengthening production, possibly until 1609. Although the continuance of the furnace is in doubt from 1588 onwards, with the purchase of Giveshiven, (Gibbshaven), by the Thorpe family in 1582, it would seem to indicate that blasting was kept up after the turn of the 17th century. Gibbshaven is a late 15th century house with many additions dating from the time of ownership by the Thorpe family.
There is no evidence that John Thorpe ever lived at Gibbshaven and it is most probable that he lived at Hedgecourt and that his son Richard lived at Gibbshaven. Richard Thorpe continued at Woodcock Hammer until 1654 and it is reasonable to assume that he needed Warren furnace to supply cast iron sows, as Woodcock Hammer would have been a wholesale outlet for blacksmiths and the ironmongers of London. It is possible that Warren furnace continued until the 1650s, but it had certainly gone by 1653, as it does not appear in the iron survey carried out then or again in 1664.
In 1748 the manor of Hedgecourt and land in this area belonging to the Gage family was purchased by Edward Evelyn, and a map was commissioned of the newly acquired land. This map does not show a furnace in Myllwood but the bay can be clearly seen. It was not until 1758 that the furnace, by then named Warren furnace started up again under Edward Raby in partnership with his brother-in-law, Alexander Master. It was about this time that the Furnace Cottages, now Furnace, were built to house a new generation of furnace workers. again, being seasonal work, the furnace workers would have eked out a living in the summer months from the small plot of land that went with the cottages. The cottages were of a light oak framed construction and show evidence of re-used timber. Several closes of cottages were leased by Sir Kenrick Clayton to Alexander Master at the edge of Hedgecourt Common, and are shown on a map of Sir Kenricks lands dated 1761, implying that they were built between the re-opening of Warren furnace in 1758 and 1761.
The re-opening of Warren furnace coincides with the last phase of the iron industry in the Weald. The Weald had traditionally supplied the London area but with the importation of Swedish iron, many of the Wealds markets had been lost. So by the mid-18th century the iron industry of the Weald was much reduced while the industry in South Wales, Shropshire and the west Midlands, away from the intrusion of Swedish iron, was flourishing. Here coal was beginning to replace charcoal in the production of iron and these areas were rich in coal therefore cutting production costs. From what had been a thriving industry of 50 furnaces and 50 forges at its peak in the Weald, only a dozen or so furnaces survived. Most of these were situated near rivers for cheapest transportation costs.However, because of its distance from a navigable waterway, the products of the Warren furnacehad to be taken to London by road. The few remaining furnaces of the Weald concentrated on casting. This was helped by the coincidence of a number of wars and the growth in Englands maritime interests, and shipping needed to be armed, as well as the trading posts that were set up. The re-opening of the Warren furnace coincides with the Seven Year War of 1756 to 1763.
Edward Raby and Alexander Master were both in the iron mongery business based in London and had considerable money to invest in the re-building of Warren furnace. Shortly after re-opening they won a contract from the Board of Ordnance to supply 400 tons of ordnance a year. This was achieved by casting guns at Warren furnace and importing shot from Bristol. Raby appears to have run the furnace side of the business and Master the ironmongery side based in London. The production of guns by Raby and Master peaked in about 1761 when the main Wealden iron producers, Harrison & Co., were in decline. Unfortunately, Raby and Master went bankrupt in 1764, although there is evidence that it was the iron mongery side of the business that was at fault. Within 18 months Raby was back up and running at Warren furnace and by now he had bought out the smaller furnace at Gravetye which had been run by William Clutton.
Raby was later partnered by a Mr Rogers at Warren furnace, and they did a great deal of business with the Board of Ordnance, supplying cannon and mortars for the army and navy. They did a similar amount of business with the East India Company and with a few foreign governments. Over the space of fifteen years Raby did over £40,000 worth of trade, a substantial sum for the period. Between 1762 and 1769 Robert Knight, a carrier of East Grinstead, did a considerable amount of business carting guns to Woolwich and returning with coal which was probably used for drying gun moulds.
There are no complete surviving blast furnaces in Sussex, so it is difficult to say for certain what Warren furnace would have looked like. A drawing of Beech furnace, near Battle, on a 1724 map of the Battle Abbey estate,in East Sussex Record Office, gives us a good idea. There are also few surviving records about Warren furnace so piecing together its history is difficult. What is known is the site was arranged in a pattern common to most post-medieval water-powered furnaces, a valley embayed or dammed at its narrowest point with water courses on both sides of the site. The probable site of the furnace is at the east end of the bay where there is a prominent depression, which may be the remains of the wheel pit, close to a brick-arched culvert at the base of the bay, but subsequent rebuilding has covered the original arrangement of buildings. When Warren furnace was casting guns it would have had a casting vault; a shaft with a table at the bottom that could be adjusted for the length of barrel required. This shaft would then be packed with earth to keep the mould stable during the casting process. There is also evidence of a boring mill at the site and it is documented by Robert Knight that guns were brought from Gravetye furnace, with their heads on, to be bored at Warren furnace.
The boring mill was used to ream or shape the interior of a cannon cast hollow. Indications are that in the 18th century Warren furnace was carrying out this process as it was not unusual for various races to have culverts beneath a working site, and the remains of possible access manholes have been found at Warren furnace. The boring mill consisted of a carriage or trolley to which the cannon was securely fixed with chains or ropes, and which was pulled up to a revolving bar fitted into a water wheel. The trolley was set low for ease of loading and the windlass was raised to about waist height to facilitate handling. A building would probably have been found on site in use as a shelter for the lengthy job of sawing the heads of cannon. Boring bars were required in different lengths and diameters and would also have been stored on site.
In 1770 Raby diversified his business by undertaking the casting of bronze ordnance. An example of one of Rabys bronze pieces is on display in the Army museum in Madrid. The bronze mortar there has a 22-cm calibre, 51-cm bore, approximately 70 cm long and has the reference number 3660. It has an open pan touch-hole, above which reads RABY & CO FECIT 1771. There is also a raised crown and the initials 3. G. R. on the barrel. The Spanish captured the mortar in the town of Tetuan, (Morocco), during the North African War, circa 1859/60. There are also examples or cast iron guns made by Raby in Barbados and at Woolwich, the latter, a 12 pounder, is a rare example with a pair of lifting rings, known as dolphins, on the barrel. Raby is the only known gun founder to have the expertise to cast lifting rings in iron. He also had the ability to cast shells that were made as a hollow sphere, another highly skilled job. The bronze, used to make the mortars, would be carted down from Woolwich for use at the furnace and would have consisted of old broken or scrap guns as there is no evidence that they made bronze on site.
Edward Raby died in 1771 and the business passed to his son Alexander, who continued to run both Warren furnace and Woodcock Hammer. A legal wrangle ensued during the early 1770s between Raby and the Government who maintained that Raby had made a consignment of their guns too big and therefore wanted compensation for the use of excess bronze. Raby finally settled out of court and gave up the business in 1774. It was taken over by Joseph Wright and Thomas Prickett who also ran the North Park furnace at Fernhurst, but they ceased working Warren furnace in about 1776. By 1787 the entire iron works, which must have been considerable, were derelict, although the corn mill probably continued working until the bay collapsed in about 1865. The Woodcock Hammer stopped for a while and then continued as a wire mill, finally operating as a corn mill until the beginning of the 20th century when it finally ceased.