Rules for Cookpots

Just a short post today, but this is one of the little things that I so enjoy finding. I was writing about the massive grapen cookpots, three-legged bronze vessels that stood in the embers of the fire, at the kitchen of the Heilig-Geist-Spital in Hamburg. Through the sheer weight of metal that went into them, these were expensive and long-lived items, but they were also widespread enough for the Hanseatic cities to support entire guilds of the artisans who made them. It is from the records of one of these, the Hamburg guild of pewter and bronze casters that we get regulations for the material from which their products must be made.

Grapen courtesy of wikimedia commons

The 1357 ordinances specify:

Pewter casters are to produce bottles, bowls, saltcellars and footed dishes from pure tin without lead. However, if the tin is too hard (i.e. brittle) so it cannot be cast without lead, they may properly add a sixtieth or fiftieth part of lead, depending on how hard it is, and no more than that. They may add a fourth part of lead when casting pitchers, but if anyone should wish to have them made from pure tin, they may do that, too.

Further down, the document also records an agreement made between the guilds of the cities of Lübeck, Hamburg, Rostock, Stralsund, Wismar, Greifswald and Stettin (Szczecin) in 1354. Is specifies:

Grapen must be cast with soft copper, with the addition of half recycled grapen metal (gropenspise) or 4 Livonian pounds (28.4 lbs) of tin to each Schiffspfund (136 lbs) of copper, without any lead. Grapen must be marked.

A further agreement of 1368 adds:

Grapen may also be cast from good, hard and pure copper that has half recycled metal (spise) added. Lead must be added to this.

Finally, we have an addition made in 1444 noting the council of Lübeck agreed with its guild of bronzecasters that grapen can also be made from different materials, namely using a mixture of 3 lbs of soft copper to 1 lb of hard copper. Where the prized soft copper was not on hand, 2 lbs of Swedish copper could be used to each 1 lb of hard copper. The text adds that all soldering must be done with tin, never with lead.

At first sight, this does not make much sense to a modern reader used to the idea of getting materials in a pure and standardised form, but it provides a fascinating insight into the struggles of craftsmanship in an age before industrial supplies. Clearly there was an interest in ensuring standardisation and the purity of the metal that people paid large sums for. Notably, the regulations – most likely instigated by the city councils – also show that people were concerned about lead being added to the metal. The regularity with which this is repeated suggests it was more than the suspicion of paying high prices for substandard material. Most likely, they understood the health implications at some level.

At the same time, the regulations show a pattern that is drearily familiar today. A ban on lead, very likely initially intended to be complete, is riddled with exceptions as it faces the practical realities of the industry. After all, you could not just order any quantity and grade from a reputable copper merchant. Metal was simply not available in its pure form, and the products of different mines varied in their qualities due to their composition. Clearly, the coveted soft copper was not in unlimited supply, and after 14 years, the councils relented and allowed the use of less promising material with an admixture of lead.

The pewter casters are under a similar injunction. They must not add lead to their tin unless it is absolutely necessary – in this case the permission is given immediately, not after a span of years, but the quantity is clearly defined and quite small, between 1.7% and 2%. It is horrifying by comparison to find 25% lead permitted to be added to kannen (pitchers), but of course these were used daily and subjected to considerable stress. No doubt the practicality of making them from a softer, more malleable alloy that would not tear when bent outweighed other concerns. Lead is, after all, an extremely useful and pleasant material to work with. Wine served in these pitchers must even have tasted sweeter than from pure tin ones, and it is doubtful the creeping effect of their toxicity would have been noticeable. We are not the first generation to face this kind of test – nor to fail it.

Finally, it is not surprising that all agreements specify a large proportion of recycled metal in the bronze mix. Medieval society could not afford to be wasteful, and the economic ecosystem of a medieval city found profitable uses for almost anything. An old metal pot, broken or battered beyond the willingness of the poorest to use, would be turned into a new one.

The relevant texts (and much more material of interest) can be found in Otto Rüdiger: Die ältesten hamburgischen Zunftrollen und Brüderschaftsstatuten, Lucas Gräfe, Hamburg 1874

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