Technology of Iron Anchor-Frame Production in the Age of Exploration

Curved Linear Diode Array Imaging of a Historic Anchor Recovered from East Anglia ONE Offshore Wind Farm

“…Votruba [30] writes that: 'For the subsequent architectural development, we lack a specifically analysed frame finding', meaning an example of an anchor constructed by a process somewhere in between the incremental joining of single bars and the simultaneous forging of bundles of bars. Anchor WTG_D_154 provides a possible example of this intermediary stage, suggesting a possible date of around the later 16th or 17th centuries.…”

“…Although documentary accounts indicate that half tonne anchors were possible by the 13th/15th centuries, these appear to be exceptions for high status vessels. Votruba [30] describes a rapid increase in size during the 16th century, corresponding with the greater availability of iron due to the adoption of blast furnaces and refining forges, and the ability to efficiently work larger masses into bars with powered large hammers [23].…”

“…In the first millennium AD, anchors were likely formed by joining partially consolidated blooms or billets of metal with scarf type welds, as in the 7th/8th-century examples from the Tantura F wreck made from multiple 1.5 to 4 kg blooms [31]. From the early second millennium AD, there are examples of anchors made as composites from multiple batons, each weighing around 5-6 kg [30] (and references therein). This includes examples with complex welded structures built up in stages, like the Bremen Kogge anchor forged from long outer plates sandwiching transverse lengths of a different iron alloy.…”

“…By the 16th century, there are examples of anchors constructed by forging bars together lengthwise (lone-bar architecture) using scarf welds in the shank, although these were not very robust [30]; this includes the 16th-century example from Labrador Bay, constructed from three bars with a square section of 90 mm and around 2 m long [32]. These objects are assembled in stages with welds made individually.…”

“…By the later seventeenth and early eighteenth centuries, however, documents illustrate anchors being made by teams sledge forging together bundles of bars, and with the potential use of water-powered hammers [30,33]. The bars run the length of the intended shank, and the welds between bars are formed simultaneously at the same stage.…”