An almost completely surviving 16-chamber Hoffmann brick kiln, built by the former Horeb, Star, Blackthorn or Eclipse brickworks, and dating from 1907. It is believed to be the only example surviving in Wales. The bricks were moulded in the shed to the west, fired, and despatched to the railway siding to the east.

The moulding and drying shed serving the kiln has almost totally disappeared, but there are ruins to the NW of the kiln of an engine house. The claypit was about 100 m to the NW, and the engine house probably worked a tramway with chains.

Four of the chambers are in the curved ends, the others in the straight sides. A typical chamber is about 4 m square with a low elliptical vaulted roof about 2 m high; 15 fuel-chutes formed with special firebricks in the roof, arched flues to the centre and to the perimeter, and a charging doorway. Brick paving. Each chamber is separated by a deep rib of brickwork from its neighbours. Between the ribs the vault is of firebrick, and the fill between the vault and the flat top is of earth and rubble.

The Hoffmann kiln was an important innovation in continuous firing of bricks (also used in the manufacture of Portland cement), a multi-chamber kiln in which the fire advanced one chamber each day (controlled by the pouring in of fuel through the roof chutes). The loading and unloading took place daily in the chamber opposite to the fire. The air current entered where the bricks were being stacked, encircled the kiln, and exited through underground flues to the chimney. The 'green' bricks in the hot air ahead of the firing and the fired bricks in the cold air behind it were enabled to heat or cool gradually with greatly reduced risk of failure. The earliest Hoffmann kilns were circular with a central chimney, the later ones were on a racetrack plan, which had the potential of being extended if required.

The kiln is of the late type with racetrack plan, round-ended internally but square ended with slight chamfers externally, about 12 m by 40 m., and with chimney external to the kiln on the W side; the kiln about 3 m high, flat topped, with a strongly battered profile. Vitrified red brick construction externally. Two-ring arches to all the access doorways. One access arch has collapsed, the others are all intact. There was originally a roof over the whole kiln (seen in RAF photos), evidence of which survives on the side of the chimney.

The chimney is about 2 to 3 m square and about 30 m high, slightly tapering. Red bricks laid in English Garden Wall bond. Strengthening angles at each corner, with tie straps at 20-course intervals. Large cornice formed of 6 corbelled courses near the top. At base the chimney wall is 3 bricks thick, and reduces in thickness with internal steps at about 6 m intervals. At the foot of the chimney at the N side there is a lighting opening. The chimney is connected to the kiln by a large underground flue but no above-ground connection remains. The roof of the kiln originally extended to the chimney.

Reference: Cadw listed building descriptions.

RCAHMW, 2022.

Cofnod Safle

Hoffmann Kiln at Eclipse Brickworks, Horeb