3.2 Lead in rough ingots
Lead ingots have been found at the southeastern end of the site, which is the aft end of the ship. The ingots had carefully been stowed in a single layer directly on top of the ceiling planks (fig. 15). Many rested in their stowing position, with wrought-iron staves on top. Others were found to be lying in the sand, but their pattern of stowage is still recognisable. In total, 167 ingots have been recovered in excavation. (HyperLinkIngots) Three others are known to be held by a local diver; in total more than 200 have been observed.
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Figure 15 The wegde-shaped and angular ingots were carefully stowed in a single layer in the depth of the hold, directly on top of the ceiling (photo: P. Stassen (RCE)).
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Figure 16 Four types of ingots (drawing: Jan Nederlof).
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The excavated ingots are wedge-shaped or roughly angular (fig. 16). They are about 24 to 33 cm long and wide and 11 to 23 cm thick (av. 17 cm). They vary between 57 and 156 kg in weight, with a total weight of 16851.5 kg (n=165) (Chart 4). Most ingots fall into the range 90-120 kg, and the average is 102.1 kg. The investigated ingots represent a considerable part of the original shipment. If ingots are packed under the full extent of cemented iron bars that remain in situ, the excavated sample would be more than 30%. This is unlikely, however. Nevertheless, it is highly probable that the layer extends right up to the northwestern-most observation (between datum points 22 and 27). In that case it is unlikely that the sample represents much less than 50%. The total weight of the shipment is estimated to be in the range of 30 to 50 tons.
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Chart 4 Weight distribution of the lead ingots.
All ingots have smooth upper faces and rough bottom faces, suggesting they were made in a mould, dug out in the sand (Voormolen 1992, 20). The proportion of the wedge-shaped ones to the angular ones is 148 to 22 (n=170), which means that on average one rectangle occurs for every 6.7 wedges. Although this would mean that the angular ingots are strongly underrepresented in the sample, it seems likely that the lead was cast in an oval-shaped mould, after which the master ingot was cut into six parts (fig. 17) (Voormolen 1992, 21). The sides are smooth and do not display cutting marks.
Some ingots, both wedge-shaped and rectangular, have been incised, causing one corner to protrude (see fig. 16). The ingots with a notch occur in the proportion of 34 to 136 (n=170), which means one notched ingot to four regular ingots, suggesting that only one notch was applied to a master ingot (Chart 5). The notch was probably used to remove the master ingot of about 600 kg from the mould (Voormolen 1992, 22).
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Figure 17 Hypothetical forms of master ingot (drawing after: B. Voormolen (RCE)).
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Chart 5 Distribution of the four different shapes of the lead ingots.
Invariably, the ingots display a number of small square dents, ending in a point. These are the marks of hooks or lifting thongs, used for handling the ingots (Voormolen 1992, 29). Moreover, the ingots are freely struck with 17 different stamps (fig. 18). Only one stamp (A) is found on every single ingot, mostly more than once, up to a maximum of 43 times. It looks like a monogram of the letters T and C. An almost identical stamp was found on ingots in a Dutch ship built around AD 1531-1533 (Azier 2007, 79). It is uncertain whether it refers to a trading house or to quality. There seems to be no correlation between the weight and the type of stamps on an ingot. After A, the most frequent stamps are B (75 x) and E (49 x). All other stamps occur two to eight times. The wedge-shaped ingots with a notch have the largest variety of stamps, up to six different ones. As stamps occur on all surfaces including the sides, at least some of them were applied after the master ingot was divided into parts. Most marks seem to be merchants’ marks, of which thousands were in circulation in the 17th century. They may refer to a producer, trader, or merchant house (Kits Nieuwenkamp 1955).
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Figure 18 Stamp types on lead ingots. In the text the images are indicated with capital letters, A-D in the top row, E-H in the second row, I-L in the third, and M-Q in the last row (drawing: B. Voormolen/A. Overmeer (RCE)).
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Mark I is a cartouche with a Maltese cross; mark J is similarly designed but it is unclear what it depicts. Mark P is also a cartouche and displays a crowned eagle. These cartouches have a heraldic touch and may refer to the area and organisation of production. This is further corroborated by stamp E, which is a rectangular cartouche with the capitals ILKUS, a spelling variant of ‘Olkusz’, a town in Lesser Poland.[4] From the end of the 16th to the beginning of the 18th century, Olkusz was by far the most important lead-producing centre in Poland (Molenda 1963, 1972). Isotopic analysis, in which the composition of 14 ingots was compared with 12 samples of galena (the natural mineral form of lead sulphide, the most important lead ore mineral) from the lead-zinc-silver mines of the Olkusz region, supports this identification (Clayton et al. 2002, 303 & 307; table 2). The normal pattern of the Olkusz trade was from Krakau (Kraków) along the Vistula to Danzig (Gdánsk) on the Baltic (Molenda 2001, 88ff.).
The Aanloop Molengat type of ingot is not previously known from literature and does not figure in Willies’ (1982) typology. Similar, but not identical, are two ingots found off Cape Arkona in the Baltic (Förster 1994, 59). The Aanloop Molengat finds enabled Molenda (2001, 22-23) to correlate with a single ingot find from medieval Novgorod and to explain the variety of master ingots and their partitioning into four or six sections (secatio plumbi, in the sources). The average weight of the Aanloop Molengat master ingots of about 600 kg corresponds to ten centner (hundredweight). This correlates well with the information from which time series of production were derived, but 6, 8 or 12 hundredweight casts were apparently also applied. The notches are indeed explained as primarily for tackling and handling the master ingots. Interestingly, Molenda mentions the strategic quality of lead and prohibitions on its export during periods of war (Molenda 2001, 36). Evidently, exceptions drove production as well as trade.
A recent find on the coast of Namibia, the Oranjemund shipwreck cargo, includes a shipment of lead that appears to be very similar to the Aanloop Molengat assemblage. The published photograph seems to display both wedge-shaped and rectangular ingots with and without incisions. Their weight varies between 70 and 156 kg (Chirikure et al. 2010). Although stamps and seals are mentioned, only one unidentified seal is published. The assemblage is thought to predate Aanloop Molengat by a hundred years. A study of the stamps and isotopic composition may clarify whether it comes from the same source. Considering the ingot type, it is probable that the Oranjemund shipment, like the ingots of Aanloop Molengat, represents primary production. It is tempting to suggest that it was produced in Lesser Poland.