Search
  • Adrian J. Boas

On the Uses and Abuses of a Dull Metal


Cast lead alloy pilgrims' ampulae [The Portable Antiquities Scheme/ The Trustees of the British Museum / CC BY-SA (https://creativecommons.org/licenses/by-sa/2.0)]

As a former pencil-chewer, it is a great relief to know that the lead poisoning I got as a child came, not from the "lead" of the pencils, actually graphite, which is not poisonous, but from the yellow paint on the pencils' exterior. Graphite contains no lead, but from the beginning graphite pencils were, and have subsequently always been known as lead pencils.


In the early nineteenth century my great, great, great grandfather owned a pencil factory at 30 Wentworth Street, Spitalfields in London. The pencils he made were probably the square, wood-encased sticks cut from natural graphite that were typical of English pencils until around the 1860s. The first graphite pencils made their appearance much earlier, possibly around 1560 when an Italian couple, Simonio and Lyndiana Bernacotti made a type of pencil out of a hollowed stick of juniper wood. Although graphite was found in Bavaria in the fifteenth century, the only known deposit of solid graphite is located in Cumbria, north-west England. That is why graphite pencils were largely an English industry until 1795 when Nicholas-Jacques Conte, a scientist serving in the army of Napoleon Bonaparte, developed a means of using powdered graphite mixed with clay and fired in a kiln, thereby breaking the English monopoly. As it is still often believed that graphite pencils were invented around the time my ancestor was making them, in our family history he has been regarded as the inventor. This was a point of pride for earlier generations that found the fact that two of his sons were sent to Australia as convicts, not quite something to boast about. Of course, today, when we look on this from a greater distance, their achievement - larceny - seems, if not more honourable, certainly no less interesting.


But I wish to consider lead, the real lead, with the chemical symbol Pb from the Latin plumbum, which by the way is where the word 'plumber' plumbarius comes from (as in the past most piping was made of lead) and 'plumb-line' for the cord with a lead weight used by builders to determine the vertical. It is a dull metal: grey, heavy, dense, soft, malleable, toxic. It seems that almost everything about it is negative and that it required an imagined science, alchemy, to turn it from something base into something of value. But that is not at all the case, and in reality, lead is of great value. It is common, and so, not expensive, it is malleable, which makes it easy to form into a variety of objects, and it is resistant to corrosion. In the Classical periods it was used for making writing tablets, piping, pharmaceuticals, drinking flasks, vessels used for mixing wine, slingshot pellets and coffins. It was even mixed in powdered form with wine and foods to improve their taste. After the fall of Rome its use declined but revived again in the Middle Ages. In the Crusader period and in the Latin East it was in use for a host of functions.


Lead plates were used for roofing. At Montfort Castle a large piece of a lead plate was found in a cistern where it had fallen when the castle was destroyed by Baybars in 1271. The plating was used to prevent water seepage and guide the rainfall into pipes that carried it down to the cisterns below the ground floor. It is recorded that King Baldwin I tore down such plates from the roof of the Al-Aqsa Mosque in Jerusalem when it served as his palace, and sold them in order to refill his emptied coffers. Only one such plate was recovered at Montfort, but in all the areas that have been excavated quantities of shapeless lead fragments have been found, and many of these must have come from the plates that were melted in the conflagration that brought the castle down. Others probably came from the lead cames - channelled strips of lead used to hold the separate pieces of stained glass in windows. Another possibility is that many of these fragments were from the use of molten lead as a weapon, poured or scattered during an attack. Also, in Montfort and in many other castles and urban buildings, lead was used to attach pieces or iron to stonework when necessary. Examples of iron cramps, rings and other items set in lead can be seen at Montfort, Belvoir, 'Atlit, the citadel in Jerusalem and many other locations.


Lead was also used to make seals or bullae that were attached to official documents, and to mint small tokens that may have been used as a local currency or for some other purpose, such as in games. It was used to make items sold to pilgrims, such as badges, crosses and the small ampullae that were purchased by the pilgrims and filled with holy water or oil. Another common use of lead was in the manufacture of glazing for ceramics. The most common type of glaze applied in the medieval period was lead-based and even the popular tin-glaze was made by adding tin to a lead-based glaze. Lead produced a transparent surface covering that could be coloured with iron, copper or manganese oxides and become highly decorative. On cooking pots, it was used without colour additives, and not for decorative purposes but in order to prevent food from sticking to the surface during cooking. It was rather like the modern use of Teflon on frying pans, though with some unrealised health "benefits". Indeed, it is remarkable to consider how much lead must have been absorbed into the bodies of people living in the Middle Ages through their constant and daily use of it in cooking, eating and drinking. The symptoms of lead poisoning include such things as abdominal pain, constipation, headaches, irritability, memory problems, difficulties in conceiving children and carrying a pregnancy, behavioural problems, intellectual disabilities, seizures and death. Excessive use of this dull metal might explain much, though in all fairness, all of those symptoms can be explained by a lack of awareness of the dangers lurking behind many other useful things.


Lead glazed Port St Symeon vessels, 13th century.





57 views