Page 143 - Kennemerland VOC ship, 1664 - Published Reports

NAUTICAL ARCHAEOLOGY, 9.1
Table 3. The weight in pounds of the fothers used in various production centres in the I 7th centuv, together with the weight in kilograms of the pigs derived from these standards
Fothers lb
London 2184 Birmingham 2240 Hull 2340 Newcastle 2352 Liverpool/ChesteI 2400 Stockwith 2408 Grassington 2460 Stockton 2464 Worksop 2520 Wirksworth 2700 High Peak 2820
(No weights are known for other areas)
Pigs kg
123.9 127.1 132.8 133.5 136.2 136-7 139.6 139.8 143.0 153.3 160.0
though unfortunately the Kennemerland ingots add to, rather than draw upon, established data for the 17th century.
Production in the middle and late 17th century was almost entirely in the ore hearth, a small water-powered blast furnace using dried wood chips (white coal) as fuel, and somewhat similar to a blacksmith’s hearth. The ‘brouse’, as the fuel and partially smelted ore were known, floated on a pool of molten lead, which overflowed slowly into a reservoir or sump pot, from where it could be ladled as convenient into a mould or ‘spurr’. The rate of smelting was slow enough to allow the pig to solidify be- fore the next need be cast, thus allowing the mould to be slung from a weigh beam. Moulds were generally of stone or cast-iron, but from the ‘pouring bumps’ seen on the base of several ingots, some at least of this find may have been cast in loam or sand, the form being obtained by the use of a wooden pattern.
In the absence of data with which to com- pare the marks recorded, the most useful feature is the weights. The fairly close spread observed in the normal distribution about 140- 141 kg (Fig. 12), if the subsidiary peaks and extremes are ignored, suggests weighing at the time of casting may well have taken place. The great majority lie within 2 kg of the peak, which, when considering a combined weight of at least 200 kg for ingot plus mould, is within 1%; not so different to the error ex- perienced on our own modern spring balances.
Table 3 shows the weights of pigs and fothers (8 pigs to 1 fother) at various producing
areas and ports in England; it can be seen that the nearest weights to the mean recorded in this collection (1 40.2 kg) are just under 140 kg. Since the trade practice was for lead to be ordered by the pig, but paid for by the actual weight on the port weigh-beam, it was in the interest of the smelter to overweight his ingots, rather than the opposite, so a small skew might be expected. There is therefore a strong pre- sumption that the origin of these examples was either Grassington, which used York and Hull as shipping ports, or one of the fields further north, such as Swaledale, which used Stockton with its very similar weights for its port. Both areas are known to have had an important lead trade at this period. A cautionary note should be inserted here concerning a single ingot found in the Trent gravels near Colwick, with an almost certain Derbyshire origin; it weighed only 134 kg, as against the recorded local norms of 153 and 160 kg. It is possible that weights were adjusted in some cases to those of the in- tendedmarket.
The shape of the ingots is boat-shaped and, despite minor variations in detail, exhibits an impressive homogeneity in design. The use of such heavy weights made manual handling difficult, b u t this design facilitated slinging with simple rope slings. The weight possibly helped deter thieving, but the shape made stacking very difficult unless the ingots were supported by either wooden blocks or ship’s timbers. The weight must also have made land transport difficult, and it is likely that either a sled or a cart would have been necessary.
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