Allensford Blast Furnace

NZ 080504. A late 17th century blast furnace which survives to two-thirds height with lining intact but arches robbed and collapsed. Remains of the leat have been plotted to the west; above the unique remains of calcines. Currently being excavated by Newcastle University. (1)

That a forge existed in Allensford in 1670 for the making and working of iron is clear from documentary evidence. That it existed until around 1730 seems clear although its furnace may not have been in blast beyond around 1715. The excavation in 1977 proved the site and remains of a blast furnace which was almost certainly charcoal fired with water-powered blowing. While there is literary evidence for a bank of calciners, only one survived, its internal form being similar to late 17th/early 18th century lime kilns. (2)

Allensford Blast furnace, on N bank of R Derwent 250 metres east of bridge. Grade II. Remains of Blast Furnace, late C17 or early C18. Furnace neatly-squared stone, calciner coursed stone. Furnace is ruinous square structure with jambs and part of round arch; walls with temporary protective concrete capping at time of survey. Calciner, further up bank, has splayed wing walls flanking round-headed arch into circular kiln; kiln wall standing 3 metres high in parts. Important industrial monument, traditionally associated with the Shotley Bridge sword makers. Last use of the charcoal-fired blast furnace gave archaeomagnetic date of 1740+/-10. Excavations 1977/8 by Newcastle University. (3)

Second season of excavation August-September 1978 by Peter Brown and Stafford Linsley. Work continued in two of the three areas examined in 1977. Also trial trenching 120-130m west of furnace stack to try and locate waterwheel head race. Channel located, 1.3m wide x 0.8m deep with remnants of clay lining.
Finds included 17th and 18th century pottery and pipe bowls, slag, charcoal and ironstone pieces. Work to continue in 1979. Proposed as a scheduled ancient monument. (4)

Survey drawings made in April 1977 include: plan of excavated structures (blast furnace, calcining kiln and possible water race site) (scale 1:20); two sectional elevations through the furnace and two external elevations (scale 1:10); two sections through the calcining kiln (scale 1:20); section through the possible site of the water race (scale 1:10); details of possible voussoirs removed from tumble in the vicinity of the tapping arch (scale 1:10); elevation of tapping arch side of furnace showing relationship to internal structure of furnace (scale 1:20). (5)

Short-lived late 17th century blast furnace survives in north east corner. The roasting kiln is the nationally significant component of the site. (6)

Excavation report of second season in 1978. Work extended some of the areas examined in the previous year, but also included trecnehs across a linear depression presumed to indicate a surviving section of head race. The furnace was lowered through destruction layers to what may represent the abandonment level, the upper surface of which showed an increased density of finds which included 17th and 18th century pipe bowls and pot sherds plus a number of unidentified pieces of iron. The presumed blowing arch was shown to be asymmetric and a sand-filled cavity between the inner and outer walls of the furnace was exposed. Excavation also revealed a vertical rebate at the outer corner of the pllar and a projecting stone footing, which suggested that the furnace had been strapped with timber.
The trenches across the presumed had race exposed a narrow channel with revetments of river boulders. This was the first direct evidence for water power at the site and a possible alignment for the head race was levelled back, beyond a corn mill, to the remains of a dam on the river.
The calcining kiln was also re-examined after the removal of a large tree in front of it. The tree had not damaged the draw arch but had interfered with the working area in front of the arch. No dating evidence was found but the kiln is presumed to be contemporary with the furnace. (7)

Contemporary documents indicate the presence of an iron forge for the production of iron at Allensford by at least 1673. Archaeomagnetic dating of the furnace provides a date for its final campaign of 1740 +/- 10 years. The furnace was one of only two in the North East of England producing iron during the 17th century and the calcining kiln is the earliest surviving example of the type nationally.
The calciner and blast furnace lie within woodland on the northern bank of the River Derwent. The furnace sits on the first terrace about 20m from the river, and the calciner is further upslope on the edge of a sandstone quarry face. Following excavations in the 1970s the walls of the furnace were capped with a concrete screed to prevent further deterioration.
A walkover survey and measured survey undertaken in 2017 identified 25 features within 500m of the furnace and kiln, including a roadway and adit about 95m to the east of the furnace as well as a number of fairly amorphous earthworks, possibly spoil heaps, in the closer vicinity. The line of the leet was also identified running to the west of the furnace, though its ultimate course was not determined. (8)

NZ 080 504. Allensford blast furnace. Scheduled No ND/619. (9a)

No changes. The furnace stack has been capped to help preservation and the kiln has been back filled and appears stable. (9b)