Gunns Mill is located in the Forest of Dean at a point where the roads north from Littledean and the A4151, south from Mitcheldean and the A4136 and west from Flaxley and the A48 meet at Spout Lane.

The postcode is GL17 0EA and the OS map reference SO675159

By car it is about 20 miles/35 minutes from Chepstow, 15 miles/30 minutes from Gloucester and 15 miles/35 minutes from Monmouth. There is on-site parking accessed from the Flaxley to Mitcheldean Road (Abenhall Road) just north of its intersection with Lower Spout Lane.

The building cannot be visited until repairs are completed, but there is a viewing area near the car park and the site is clearly visible from Lower Spout Lane. There are several interpretation panels on site.

Metallic iron combines readily with other elements to form compounds such as iron oxides. Thus the metal does not occur naturally but some of its compounds, termed ores, are plentiful. To release the metal, ore and charcoal were fed into furnaces where they burnt at high temperature due to the air blast provided by the water powered bellows.

Michael Blackmore’s drawn reconstruction of a furnace, near Gilwern, shows a furnace built into a hillside with a charcoal store at top level. Water is fed from the left to a water wheel beneath the narrow sloping roof. It powers the twin bellows. The cast house, where the molten iron solidifies, is on the lower right hand side.

At Gunns Mill the placing of the three units is different: the cast house is where the drawing above places the bellows. The latter are round the corner against the left hand face of the furnace. Further left are the water supply and wheel pit lying parallel with and against the bank.

Smelting

In the furnace heat and chemical reaction combine to produce liquid iron which pools at the bottom of the furnace. From there both iron and slag (the molten rocky waste) were tapped , i.e. run out, to cool and solidify. The iron flowed onto a sand bed containing main and side channels where it formed ‘sow’ and ‘pigs’ of cast iron. It could also be poured into moulds to produce articles such as fire backs and cannons. The slag was discarded.

Although obscured by the scaffolding, the protective netting and the banners, the outline of the furnace structure is clearly visible looking west from Abenhall Road and the car park, or north from Lower Spout Lane.

The furnace was designed to take advantage of gravity – the iron ore, cinders and charcoal had to be kept dry in the bridge house at the top level before being loaded into a hole in the top of the furnace. As the charge moved down through the furnace towards the lower ground level molten iron eventually collected at the bottom of the furnace, with the waste slag floating on the top, and from time to time was allowed to flow out of the furnace into moulds in the ground (known as sows and pigs) at the lower level.

The front of the furnace is now just bare grass, with some concrete pads supporting the scaffolding, but there would have been a building above protecting from the elements.

The water wheel powering the bellows that blew air into the furnace was on the far side of the furnace – the building housing it can be seen from Lower Spout Lane to the left of the furnace against the far wall, although it long ago lost its roof. The remains of the later wheel are inside it, although public access is presently impossible.

The water from the Flaxley Brook flowed onto the top of the water wheel to turn it and then was taken underground well away from the furnace and down to the main stream in the Flaxley valley. This kept the water well away from the molten metal, which would explode in contact with water.

There were numerous other buildings at this lower level, some associated with the furnace, and others with the paper mill, but most have gone leaving little trace. The modern construction work in the far corner was necessary to stabilise the rear retaining wall of what would once have been a large dam, since filled in.

Apart from the scaffolding and cladding of the main structure, the Trust has undertaken several construction projects to stabilise the structure. These include, apart from the stabilisation at the rear of the site, rebuilding the wall behind the wheelpit, which was in danger of collapsing into it, and partially rebuilding the wall this side of it, and subsequently dismantling the north wall of the bridge house and rebuilding it on a stronger foundation, capable of supporting the roof.

Now, in 2024, with the most precarious elements of the masonry stabilised and other areas securely propped, attention has turned to the timber framing and roof construction. A generous grant from Historic England (see news items) is largely funding the repair of the four original trusses of the bridge house roof, dating from 1681. Once this work is done, we anticipate a further project to reinstate the original slate roof, thus making this unique survival structurally sound and complete.

Although of the same age, the timber structure of the drying house on top of the furnace is much larger than that of the bridge house and lacks the stability of the masonry walls. Only when the bridge house is stabilised can design start for the repair of this magnificent example of the skill of 17th century Forest carpenters– approaching 350 years ago!

The conservation of Gunns Mill was always destined to be high on the agenda of any organisation interested in the care of our local heritage. The challenge is the cost of the work necessary and the identification of sustainable end use. To this end the Trust has:

Liaised with English Heritage (now Historic England) and sought appropriate consents where needed.

Commissioned an ecological survey

Rebuilt missing boundary walls, fenced and gated the site. Removed scrub and litter.

Commissioned a structural engineering site survey, advice and specifications

Commissioned archaeological surveys including ground radar and resistivity

Commissioned detailed building recording surveys and research

Commissioned inspection and maintenance of the scaffold and shoring.

Re clad the mill building with a new weatherproof membrane

Created car parking space, site office & store, and landscaping

Created a viewing platform with interpretation for the public and visitors

Commissioned conservation architects Caroe & Co of Ledbury to draw up options

The Forest of Dean had plenty of wood to make charcoal and readily available iron ore, becoming the centre of the iron industry in Britain in medieval times. Blast furnaces, introduced from Europe to the Sussex Weald at the end of the 15th century, could produce much larger quantities of iron than the earlier technology, and once the Wealden furnaces used up the available ore and timber soon spread to the Forest of Dean, which had more furnaces than anywhere else in Britain in the 17th century.

Gunns Mill furnace was built by Sir John Winter in 1625 on the fast flowing Flaxley Brook that had a number of water mills, including William Gunn’s fulling mill in the 16th century, hence the name. The Winters were on the losing side in the Civil War and the furnace was put out of action in the early 1650s, but by 1683 the remains had been rebuilt.

The old structure was raised higher and strengthened by the addition of cast iron lintels, with the dates 1682 and 1683 cast in the metal. A new bridge house, in which the charcoal, cinders and iron ore were stored before loading into the top of the furnace, has been dated by dendrochronology (tree-ring analysis) at the same time. Although long gone, the wheel pit shows evidence of a 22’ diameter water wheel powering the bellows.

This work was apparently done by a George Scudamore and Henry Hall from Highmeadow (near Whitecliff, Coleford), probably in association with the Duke of Beaufort.

The iron works was purchased by the Foley family in 1701, and production records exist from 1705 until the last recorded production of iron in 1732 Production in 1705-6 totalled 781 tons, of which 9 tons were ‘bowkes’, probably including lintels like the dated ones here, and 1 ton firebacks.

By 1743 the structure had been converted into a paper mill by Joseph Lloyd, with the wheel’s power used to crush rags, and the centre of the furnace was turned into a stair well. The bridge house was extended as a half-timbered structure for drying paper onto the top of the furnace and many ancillary structures built or converted. Over the years a wide range of paper was made, including coloured paper, brown paper and even blotting paper.

Shortly after 1880 all the machinery had been removed. The upper part of the furnace was used for milking cows from the 1940s and until the 1980s housed pigs and chickens. A small water wheel was installed in the early 20th century to operate a cider press.

The importance of the furnace was recognised by listing in 1955, and later by the respected local historian and Senior Verderer Cyril Hart, who described it in his 1971 The Industrial History of Dean as “the best remaining furnace of the earliest phase of British blast furnace practice”, although it was by then in very poor condition. Hart stated that “If the structure is not to collapse soon it needs urgent attention.”

Despite its importance Scheduled Ancient Monument and Listed Building consent was granted in 1992 for the building to be converted to a two-bedroomed house. William Parker, a local resident, went to see it and had an offer to purchase it accepted the same day, to save it from this fate.

The building was then shored up externally and internally to prevent further collapse, and eventually its importance was recognised, resulting in English Heritage funding a full scaffolding of the building in 2000, to protect it from the elements. Once the bridge house timbers had been dated to the 1680s, making it the oldest such to survive, and the uniqueness of the slag still present on the lining from the last firing in the 1730s become apparent, Gunns Mill was recognised as being of national, if not international importance.

At the suggestion of the then Forest of Dean Conservation Officer, Bill Cronin, the Forest of Dean Buildings Preservation Trust was formed by Kate Biggs, Jim Chapman and Laura Stevens, with a view to taking on Gunns Mill as their first project, and William Parker donated it to the Trust in 2013. Ian Standing, the leading industrial historian (and currently Senior Verderer), William Parker and others joined as trustees.