Saturday, 1 August 2015

Experimental Iron Smelting with the Wealden Iron Research Group


I was thrilled to be invited to attend an experimental iron smelt by the Wealdon Iron Research Group, and also have an opportunity to actively participate in parts of the smelting process. The Wealden Iron Research Group [WIRG] have been carrying out research and experiments with respect to the iron industry of Sussex since 1968. Undertaking landscape exploration to locate, survey, and sometimes excavate iron making sites, the group also collect iron ore and slag for smelting and research analysis (WIRG online).
The weald was a nationally important area for iron working, in the Iron Age, Roman period and Middle Ages - with the last Wealden furnace closing at the start of the C 19th (J Hodgkinson 2002 via WIRG online 2015).WIRG undertake their iron smelting, at an experimental bloomery in Ashdown Forest, using self-collected iron ore and try and reproduce the irons and waste of the historical Weald iron industry.
The notes below are taken from observation and discussion in the field, and the science from the WIRG website (follow the link below). Iron carbonate (Siderite Ore) is broken into small pieces, and roasted in a wood furnace changing the carbonates to oxides, and driving off water and carbon dioxide. The resulting iron oxide is left to cool, then broken down into smaller pieces.
Iron carbonate (Siderite ore)




Smelting of the iron oxide takes place in the "cylindrical shaft furnace" Or bloomery - which is pre-heated overnight with a wood fire. In the morning the furnace is again preheated and then a layer of wood is placed within its base to capture the iron "bloom". The bottom entrance of the furnace is then bricked up and sealed. Charcoal is placed in the furnace via the top of the shaft, is fired and continues to be added to bring the furnace up to a working heat. Air is introduced to the furnace through a tuyere (pipe), on this occasion via an electric pump. The tuyere also provides a line of sight to monitor the colour temperature of the furnace. Modern thermocouples monitor the internal heat of the furnace.

Charging the bloomery


View through the tuyere


When the furnace is at sufficient temperature - the iron oxide is added in stages, along with more charcoal in a fixed proportion. Temperature is maintained to produce a molten "slag" which carries the solid iron to the bottom of the furnace, where it is deposited as an iron "bloom”. The slag is then tapped to release it from the bloomery.

Tapping the slag

The furnace is opened and after much manipulation the iron bloom is separated from the furnace wall, then removed and immediately worked with hammers to drive out slag and forge the loose iron particles together. The iron is repeatedly re-heated during this process in a small hearth charged with charcoal from the forge.



On the day Josh Hall a local Blacksmith was also visiting the smelt for the first time; Josh was able to work the hot iron and begin the process of consolidation. It was a very exciting process to witness, made even more so when I joined Josh as his "striker" - attempting to make the second hit on the iron, in the place of his first hit - a process continually repeated - until a small rectangular piece of iron was shaped, then left to cool slowly in the embers of the hearth.



A cracking way to end the day, and a cracking first-hand experience of experimental archaeology!

Many thanks to Tim Smith (for the invite) and the "smelters" of the Wealden Iron Research Group for a truly memorable day.

Wealdon Iron Research Group can be found at: Wealdon Iron Research Group

Josh Hall (Blacksmith) can be found at: J Hall Forge

Sunday, 5 July 2015

Corfe Castle .. gatepost as interpretation ..

The entrance to the Ring and Bailey castle field, at Corfe Castle has an interesting carving, which is incorporated into the gate post itself. The carving of Oliver Cromwell marks the role that the earthworks of the Ring and Bailey castle originally built in 1139, went on to play in the English Civil War of 1642 - 1651. During the war the Parliamentary Army, used the site for a gun battery and successfully laid siege to and then wasted Corfe Castle.

The Ring and Bailey castle itself dates to an earlier period of civil unrest when in 1139 King Stephen built a siege fort to challenge Baldwin, who held Corfe Castle in rebellion. The siege was abandoned following the invasion of Robert of Gloucester, who landed at Arundel, with 140 knights. An act of aggression which started 14 years of Civil War, and ended with the loss of Stephen's throne.

http://www.dorsetlife.co.uk/2008/02/the-other-siege-of-corfe-castle/

http://www.british-history.ac.uk/rchme/dorset/vol2/pp52-100

Saturday, 23 May 2015

Let there be Rock .. Art! - Northumberland and the briefest of archaeological adventures.

"One night in a club called the shakin' hand
There was a forty-two decibel rockin' band
And the music was good and the music was loud
And the singer turned and he said to the crowd
Let there be rock'

Let There Be Rock, (1977) Angus Young, Malcolm Young, Bon Scott

Not just a dirty trick to get a cheap rock reference into a blog post about Neolithic Rock Art .. this was the song spiralling in my head, as we climbed the short ascent towards the Lordenshaw Iron Age hill fort; excited at the thought of exploring the cup and ring marked sandstone boulders that can be found on the slopes around and beneath it.

Contrary to our usual preparedness on such days, we lacked an O/S map for this particular area; thus relying on mobile technology we exploited the information provided by the Rock Art Mobile Project [RAMP] which can be found at: Rock Art on Mobile Phones and the more than useful QR codes attached to the way-markers on site, from which we downloaded specific directions for each of the three primary stones of interest: the Main Stone, Horseshoe Rock and Channel Rock.

 These rocks contain a mosaic of hand-carved motifs, of cups, rings and grooves.

Main Stone
Main Stone - detail
Main Stone - detail


carved stone - south of Main Stone


The Horseshoe Rock is so named because of the curved horseshoe lozenge which contains within its central space numerous cup holes. Tracing of spirals and grooves also occur on this rock.

Horseshoe Rock

Horseshoe Rock - detail

Horseshoe Rock - detail

Horseshoe Rock - detail


The largest rock the Channel Rock being spectacular in the depth and length of the central carved groove which flows downslope from a close series of rings at the top edge of the stone.

Channel Rock - from above


Channel Rock - from below


Channel Rock - detail

Carved rock Or natural water weathering?

Carved rock - faint cups and associated  carved Or natural water channels?


There are over a 100 carved rocks at Lordenshaw (www.bradshawfoundation.com 2011), which are dated between the early to late Neolithic period some of the stones incorporated into or associated with later Bronze Age burial cairns (Frodsham, P. 2006).

Lordenshaw rock art sits within a close knit and wider archaeological landscape incorporating the Bronze Age cairns, Iron Age hillfort (occupied later with Romano-British settlement), and the remnants of a medieval Deer Park wall (Rock Art on Mobile Phones).

The richness of the archaeology was more than matched by the soundscape of moorland birds, competing for our attention, as we explored the rocks. Serenaded by multiples of competing skylark (Alauda arvensis) in full song, and the constant shrilling "chip-chip", "chip-chip", "chip-chip" of parachuting meadow pipit (Anthus pratensis). Overlooking the moorland of Garleigh Hill we enjoyed the bubbling song of curlew, as they flew between the valley and the hilltop, whilst buzzard (Buteo buteo) and kestrel (Falco tinnunculus) hunted above them.

A distant cuckoo (Cuculus canorus), called it's own name in the woodland to the south, the first of our year and long overdue. Heading back downhill towards the car park, we disturbed a young hare (Lepus europaeus), which promptly disappeared to ground only metres away from us? The briefest of hare searches called off as a red grouse (Lagopus lagopus) croaked on Simonside, and we headed across the road and uphill to find the bird itself. With our eye eventually in, we managed to find three red grouse, within a short distance of each other, along with a smart male wheatear (Oenanthe oenanthe) it's white arse flashing in sharp contrast to the moorland heather.

Red grouse - record shot only (cropped)


References:

Bradshaw Foundation (2011), (Online), Lordenshaw, Rock Art, Northumberland Found at: http://www.bradshawfoundation.com/british_isles_prehistory_archive/northumbria_rock_art/lordenshaw.php

Frodsham, P. (2006), In the Valley of the Sacred Mountain, An Introduction to Prehistoric Coquetdale 100 Years after David Dippie Dixon, Northern Heritage Publishing, Newcastle Upon Tyne

Rock Art on Mobile Phones (Online), Lordenshaw, Found at: http://rockartmob.ncl.ac.uk/main/r/