9.5.1 Metalworking

Many iron-working sites with evidence of slag and charcoal are found throughout the Highlands, but dating is dependent on radiocarbon analysis of the charcoal (Table 9.5). However, this analysis provides dates for the timber, which could be much older than the actual iron-working. For example, at Fasaigh on Loch Maree, Wester Ross, the ironworks are post-medieval, but radiocarbon dates include three medieval dates, based on pine and birch charcoal (MHG7921; Photos-Jones et al 1998). In most cases no associated structures are evident.

A good overview on the processes from smelting to smithing, and the evidence resulting from each, can be found in Spall and Mortimer (2016). The first stage in the process, smelting iron ore, is evidenced by bloomery mounds, usually identified by slag (the byproduct of the smelting), charcoal and sometimes a preserved mound. A project investigating bloomery mounds in the Scottish Highlands is summarised in Photos-Jones et al (1998) and Hall and Photos-Jones (1998), building on other work by Wordsworth (1993).

Relatively few bloomery mounds have been dated, but the evidence shows probable widespread activity. Of three iron slag heaps investigated in mid Ross which had samples dated, all were dated to the medieval period providing evidence of iron working throughout the period. Birch and alder were used for charcoal (Wordsworth 1993b).

Wordsworth (1993b) argued that due to the bulky and friable nature of charcoal, ironworking is likely to have been carried near to the wood source. Many of the locations in the Highlands also suggest that bog iron rather than mined ore was used as the raw material. Iron workers would therefore have sought out good sources of bog iron with trees for making charcoal. As a result, the bloomery mounds do not necessarily indicate the site of missing townships, but further exploration of them is required and may be rewarded with some tangential evidence for medieval rural settlements (Atkinson 2003, 42). Place-name evidence and the location of bloomery mounds in remote locations with no nearby arable land in the northern Highlands suggest that bog ore was of some importance and that peat was used in the absence of trees.

At Loch Doilean, Sunart in Lochaber, five charcoal-burning platforms were excavated, providing dates from Mesolithic to post-medieval times. Platforms 2 and 4 dating to the 11th – 14th centuries, showed activity burning oak and hazel. On Platform 2 a central oval hearth survived. Interestingly its fill was peat, suggesting blanket peat had developed after the site was abandoned. One platform had an inner and possibly an outer ring of postholes suggesting a structure probably dating to this period. One wall may have been turf. These platforms can be compared to similar medieval ones excavated in Argyll. Based on the evidence, Ellis (2016, 9-10, 40-42) suggested differences in techniques for constructing the platforms, with the medieval ones being smaller and created from a levelled fan of crushed stone cut whereas the post-medieval platforms were recessed with the floor constructed from excavated material. If this pattern is confirmed with more dating, it would allow for a general type of charcoal burning platform to be identified during surveys. Charcoal could have been used for a number of purposes, but clearly at this period it was in demand for metalworking. However, further investigation of sites and their contexts is needed.

At Glen Docherty in Ross-shire, a charcoal burning platform (MHG50922) dating to the 15th to 17th centuries based on birch and hazel charcoal was located near to a bloomery mound (MHG7923). This mound produced dates of 11th to 13th centuries, and then the mid 15th century, with the earlier dates for the bed of ore. The bloomery mound used birch charcoal. It was unclear if the earlier dates for the bloomery mound relate to early activity, or possibly the use of old wood (Johnson et al 2006).

Slag was found at Castle Street in Inverness dated by other finds to the late 13th and early 14th centuries, but there was no evidence of a bloomery hearth. Smelting is not normally what one would expect to find in a burgh. At the end of the medieval period there was evidence of smithing. Much-disturbed late medieval furnaces were found, but intriguingly no metalworking debris, leading to speculation that the furnaces may have been for heating crucibles, or indeed for other industrial activity that required heat, such as dying. Structurally the furnaces displayed a range of designs, again suggesting the possibility of multiple functions (Spearman 1982; Wordsworth 1982).

Excavations of medieval smithies are not common; consequently, the evidence from Cromarty, Portmahomack and Eilean Donan Castle is important. The smithy in the burgh of Cromarty preserved postholes and daub for the walls. Hammerscale distributions indicated the position of the anvil. The remains of a small smithing hearth made from three small upright stones surrounding a base were also found. Further details and dating are awaited (Vawdrey nd, 14). There is also limited evidence of smelting (Steven Birch pers comm).

The more rural settlement at Portmahomack also had evidence of smelting and smithing in the medieval period, and then in the 15th to 16th centuries. A smithy was excavated, together with a range of iron smelting and smithing slags. There is also evidence suggesting bronze working, including copper-alloy vessel repair, perhaps by an itinerant smith. The smithy is thought to have been roofed and open-fronted, though archaeologically the building left only a superficial footprint. Unusually large smithing hearth bottoms were found and a large selection of slags including micro-slags indicated both smelting and secondary smithing (Carver et al 2016, 314ff).

The smithy at Eilean Donan Castle (MHG45372) is roughly contemporary with that at Portmahomack, and has similarly large smithing hearth bases. It was used to repair and possibly make large iron items, possibly even as an armoury (Case Study Eilean Donan Castle ; Clark et al forthcoming). Evidence for non-ferrous metalworking were also identified, and a significant quantity of crucible fragments recovered from a late medieval midden.

Smithing hearth base from Eilean Donan Castle. ©FAS Heritage

Less well-preserved smithing evidence was found at Dornoch on a site which had extensive metalworking in the early medieval period (MHG28197). The possible hearth was packed full of charcoal, slag, hammerscale, and furnace or crucible wall. Radiocarbon dating of a hazelnut shell in the fill provided a date from the 15th century, but there was also medieval pottery on the site, and a range of medieval metal-detected finds nearby, all pointing to activity in the medieval period (Coleman and Photos-Jones 2008, 9).

From the Norse area, there is evidence of slag and bog iron in Building 3 excavated by Curle at Freswick, suggesting a possible smithing area, but there was no direct dating evidence (Curle 1939, 81; Batey 1982, 49). In addition, at the northern part of the Links at Freswick, RCAHMS recorded a structure where the floor was strewn with slag (Batey 1987, 93-4; 1995, 87), although it was of uncertain date.

At Home Farm, Portree on Skye (MHG51648) waste in pits suggests smithing took place nearby. Most are undated, but at least one pit is medieval (cal AD 1280-1420), containing hearth bottoms and slag, but no charcoal (Suddaby 2013, 51). A midden with slag on Skye at Ashaig near the church was dated to the medieval period (MHG35894; Hardy and Wickham-Jones 2009, SFS6). Other church sites have also produced metalworking evidence including a field near the church at Ascoile in Strath Brora, Sutherland (MHG11025) but the site is without dating evidence.

The role of the smith in medieval Highland society, especially in the clan system has been explored by Atkinson (2003).

DornochS15th centuryPossible hearth, with slag, hammerscale, furnace wall, charcoalMHG28197; Coleman and Photos-Jones 2008, 9
PortmahomackERvariousSlag, evidence of horseshoes and horseshoe nails; Smithy 15th to 16th centuryCarver et al 2016, 313, 314-5
CromartyERAwaiting datesSmithy , and some slag related to smelthingVawdrey nd; S. Birch pers comm
Inverness (Castle St)IDating by findsSlag, lead workingMHG3673; Wordsworth 1982
Abhainn Srath RainichMR1310-1455Bloomery. No trace of hearthMHG17991; Wordsworth 1993b; GU-3462
Allt A’Bhealaich MhoirMR1397-1482Bloomery mound with slag and charcoalMHG17994 Wordsworth 1993b; GU-3464
Allt RuachMR1223-1394Bloomery; extensive siteMHG18085 Wordsworth 1993b; GU-3463
Creag Bhuidhe, Glen DochertyMR1052-1267
1304-1438 1441-1631 1453-1635
Bloomery mound, no structures or hearthsMHG7923; Johnson et al 2006; Poz-100034; Poz-10298; Poz-10333; Poz-10330, Poz-10839; Poz-11170
Urquhart CastleIMedieval potteryPit with Medieval pottery, fragment of a bellows nozzle; situated away from the castleMHG3265
Eilean Donan CastleLochalsh1450-1640Excavation revealed iron-smithing with an in situ hearthMHG45372; Clark et al forthcoming; Case Study; Eilean Donan Castle l; SUERC-96819
AshaigSkye13th centurySlag in shell middenMHG35894; Hardy & Wickham-Jones 2009, SFS6; SUERC-2443; SUERC-2444; SUERC-2445
Home Farm, PortreeSkyeFour dates spanning 1270-1420Pit 116 fill with hearth bottoms and slagMHG51648; Suddaby 2013; GU-17461; GU-17459; GU-17460; GU-17458
Table 9.5  Dated ironworking sites
All dates cal at 95.4% probability. For full details of dates, see Datasheet 2.1

Little production evidence exists for metalworking in other metals, but some was taking place at Portmahomack. At Cromarty there is also evidence of small scale lead casting (Steven Birch pers comm). It seems likely that a local form of copper alloy annular brooch was produced in the southern Highlands, some with distinctive decoration, but no manufacturing evidence survives. Interestingly, the brooches were made in different ways, some were cast and some cut from sheet metal suggesting different workshop traditions (see TT report 77/13, attached to MHG61308). Further detailed investigation of the metal detecting evidence from Dornoch and the southern Highlands might identify additional insights into production.

Targeted pXRF and SEM analysis of crucible fragments from a 14th century midden excavated at Eilean Donan Castle has confirmed a range of non-ferrous alloys being worked including brass, leaded brass, leaded bronze, and silver and gold (Clark et al forthcoming).

A bell-casting pit, at Portmahomack dating to AD 1040-1260 (OxA-10536) and associated with Church 2, shows these skills and the technology were available at that time (Carver et al 2016, 290).


Case Study: Eilean Donan Castle

Leave a Reply