Modern information that helps us understand casting practises

Exhibit A, the phase diagram for a copper- tin alloy, usually known as bronze (Stolen from wikipedia or wherever):

 

Bronze phase diagram

Along the bottom is the weight % tin, i.e. if the object weighs 1kg, and is 50% tin, there is 500g of tin. Sure, that doesn’t seem as scientific as going by mols, but then a lot of metallurgy harks back to before it was properly integrated into modern chemistry. Continue reading

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Latten maille and the uses of brass in war

And lots of other latten in war gear.

I was browsing through “The medieval inventories of the Tower armouries 1320-1410”, a PhD thesis by Roland Thomas Richardson (Which can be downloaded from the British Library ETHOS service), when I found various mentions of latten. Latten in that period was a copper alloy with mainly zinc and other elements.

Quoting from “Medieval English Industries”, page 82,

“The contract for the mid 15th century effigy of Richard Beauchamp in St Mary’s Church, Warwick, specifies “the best latten”, and analysis has shown this to be a copper-zinc-lead-tin alloy: 84.3% Cu, 9.4% Zn, 2.2% Sn, 1.4% Pb, and the remainder including nickel, iron, antimony, arsenic and silver.”

It is attested as being hard as bronze, and shiny.

Thus one of the uses mentioned by Richardson from the inventories, is to decorate the edge of maille shirts, which you see worn by quite a few re-enactors, the shiny brassiness showing up well against the darker iron or steel. (page 39 of the thesis)

Cap a Pie, who sell maille for re-enactors, sell individual rings for making your shirt or standard look prettier: http://www.capapie.co.uk/index.php?route=product/category&path=59_75

Weirdly though, in the Tower inventories and accounts, there is mention of latten maille shirts! A shirt made completely of latten would not be as strong as iron or steel, so I wonder why. (Pages 41 and 44 of the thesis)

The other use on armour is as a latten border, presumably some sheet riveted onto the iron vambrace (page 78 has a photo)

Latten also crops up as horse armour.

Oddly it is also used, e.g. on page 110, to make fletchings for springald bolts! I presume that they were better able to cope with the stress of use? The other use related to springalds is in 7 nuts of latten, purchased for making 7 springalds. I think the nuts they mean are the ones that hold the long brass rod which is turned to pull back the arms of the springald. Thus they would have been large, strong nuts. (page 111)

Page 167 – There is mention of 10 moulds of latten for casting lead balls for firing from guns. Ten is quite a lot and would enable fairly rapid production, although each mould would surely take a minute or two to cool down when cast into, due to the lead taking a long time to cool.

The title though is a bit of a cheat – what they called brass usually included bronze, the latter word not being around in medieval times. So cannon were made of brass, only they meant the strong 10% tin-copper alloy. There is several mentions of them in the inventories, and usefully, of the people who made them.

Page 166 mentions a small gun of copper purchased from John ‘brazier of Cornhill’ in 1361, and of course by copper they must mean bronze, since only that could take the strain of the gunpowder. Technological terms then were not as definite as they are now, although at other places in the accounts the guns were said to be made of bronze. A brazier was basically a foundryman, someone who cast in bronze or indeed brass, into moulds, whether of stone or clay or suchlike.

The earliest accounts I know of from Scotland of such practise are in the reign of James IV, the 1490’s, when a potter made a mould for casting a gun in. A potter being someone who made metal cauldrons, i.e. pots. There isn’t that much evidence surviving for potters in Scotland, but there must have been some.

So, it is amazing what turns up in peoples research. I urge you all to search through ETHOS to find PhD theses of interest.

My philosophy of manufacture of reproduction stuff

Sorry about not posting for a while, I’ve been busy and progressing lots of things at once so nothing is quite finished yet.

I decided ages ago that I would make not direct copies of medieval and Tudor stuff, but attempt to make similar objects. Not only because starting from scratch gives a better understanding of the processes and knowledge required, but also because given the massive variety of surviving objects, I think it pointless to try and produce an exact match to one specific one. Yes, all buckles are buckles, but when you look more closely there are many variations between them, due to the use of many different moulds in different towns over a century or many different copies made. It is the latter I am aiming towards, i.e. how a craftsman would replicate something that is, say, new to town or seen as the latest fashion coming from London. Or that a competitor has designed. Therefore my replicas are often a bit different in size or precise shape.

An example of such variation can be found in the MoL book “Dress Accessories”, where they list 39 medieval pewter buckles excavated in the city of a similar design, i.e. “raised, bevelled band along centre of frame and beading along edge”.. Their diameters range from 21 to 24 mm, which suggests to me at least 3 different stone moulds or else one mould slightly recarved after every few hundred castings due to erosion of the stone, in which case the depth of the buckles should change quite a bit as well. I have trouble believing that each design of buckle would be proprietary to one pewterer or girdlemaker; that they are not helps explain the variation in shape and size. The two they do illustrate have different numbers of beads around the edge and a slightly different cross section.

There is another very geeky reason not to make your reproductions identical to originals, otherwise people might mistake one for the other or try to pass them off as originals. This has accidentally happened to a reproduction potter I know, although it didn’t involve any money, just mis-identification.

Books, blogs and communicating knowledge to the public

This blog as yet has few readers; perhaps at some point I will be swamped by school pupils looking for information they can steal for their essays. But thinking about it, this lack of interest is part of wider issues to do with the means of communication.

The first example is that this blog covers archaeometallurgy, i.e. historic artefacts made of metal, their manufacture and their place in society and use by people. As far as I know, the only general book on the topic written for the general public was Ronnie Tylecote’s “History of Metallurgy”, which was first published in 1976 and an updated version in 1984.

It would be nice to know there was a more recent book of this type, but people are still using it as a reference on wikipedia, and I am sure I know of an error or two in it, because actually archaeometallurgical knowledge has greatly improved since the early 1980’s. Just in Britain we’ve had the publication of lots of London digs, putting metal objects of various sorts into their context and period; in Scotland there’s the Perth High street digs. There have been numerous PhD’s on archaeometallurgical topics, and a thriving society, the Historical Metallurgy Society: http://hist-met.org/

which journal has many interesting articles on the manufacture and use of iron, copper, gold, silver etc. In fact Tylecote was the founding father of archaeometallurgy and helped found the society.

http://en.wikipedia.org/wiki/Ronald_F._Tylecote

What all minority interests have trouble with over the decades is getting funding and disseminating information. Hence this blog and my re-enactment presentations. But my self appointed task (One which is also quite fun) is made a little harder by the paucity of publicly available information.

Another example of the issue is the book “English Medieval Industries”, edited by Blair and Ramsay. Whilst it is available on google (http://books.google.co.uk/books/about/English_Medieval_Industries.html?id=PDLPX7J8kW8C) that is not a full copy, so frustratingly you can’t get at all the information.

Amazon has copies from £42 upwards into the hundreds, because it was first published in 1991 and a paperback edition done in 2001, from which my copy comes, and it cost £19.95.

So the information in it is now 25 years old!

It is a standard reference work for anyone wanting to learn more about everything from cloth manufacture to foundrywork, but the sources and such are more than a generation out of date. Whilst I think the information given and the general conclusions are accurate enough even now, any attempt at public education should include more up to date sources, which in this day and age would include web links, even although they are often subject to rot. There is also the simple fact that EMI is out of print now and unavailable to the general public; if you are luck your library will have a copy, although due to cuts that is now extremely unlikely.

Fortunately, Copac indicates that there are copies at 31 British libraries, including the NLS, NLW, BL and university libraries. So if you really want to you can find it, but most people won’t know of the fact that you can get into University libraries even as a member of the public.

To summarise – I think there’s a disturbing lack of modern public friendly sources of archaeometallurgical information. Whilst the archaeometallurgists I know will happily talk to anyone about the topic for as long as their interlocutor can stand it, there simply doesn’t seem to be much that is easily available to the interested member of the public.

There is a great deal to be found on less well known places like http://www.academia.edu, but how many people know of it? I know of no other blogs like this, although some of the old SCA websites have information and write ups from 10 or 15 years ago. A lot of information is also found by careful searching of groups on the likes of facebook (E.g. this French experiment on crucible steel, written in English – http://ceroart.revues.org/2557#tocto2n1), but ultimately I have the impression that the subject is stuck in a ghetto. We need more communication and examples and books and other sources, to let everyone know how interesting this subject is and of course ensure they are properly educated.

TV programs sometimes cover it, for instance there was that well done documentary a couple of years ago on the bronze crossbows found with the Terracotta warriors, which really put archaeometallurgy centre stage. But that is about it. A fe minutes on Time Team or such programs really isn’t enough.