Brass!

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Charles13
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Brass!

Postby Charles13 » Wed Oct 24, 2012 11:52 am

I have a query about the use of brass in the medieval period. Many people in the reenactment world use brass objects for a whole range of uses: pins, rivets, buckles etc. However I have been told that 'no they didnt have brass as there wasnt a source of zinc'! Is this true? Its annoying as many finds are simply called copper alloy, without giving any indications of the makeup of said alloy. Should we only be using bronze? I'm only aware of brass and bronze as copper alloys in the broadest sense.



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Re: Brass!

Postby Medicus Matt » Wed Oct 24, 2012 12:30 pm

Charles13 wrote:I have a query about the use of brass in the medieval period. Many people in the reenactment world use brass objects for a whole range of uses: pins, rivets, buckles etc. However I have been told that 'no they didnt have brass as there wasnt a source of zinc'! Is this true? Its annoying as many finds are simply called copper alloy, without giving any indications of the makeup of said alloy. Should we only be using bronze? I'm only aware of brass and bronze as copper alloys in the broadest sense.


Depends which bit of the medeival period you're talking about (given that it lasts for about 1000 years, from the end of the Western Roman Empire). Copper-zinc alloys were widely used throughout Western Europe from at least the 1st century BC well into the post-Roman/early medeival period, presumably adopting the material from the Middle East (there are Middle Eastern brass artifacts dating back to the 11th century BC). The earliest examples were presumably made using naturally occuring copper ore rich in zinc (some occur with zinc content as high as 20-25%), with later brass being made using calamine (a naturally occuring mix of zinc carbonate and zinc silicate).

Perhaps that's where the notion that there 'wasn't a source for zinc' comes from? Metallic zinc doesn't occur naturally and it's not produced in the West until the post-medeival period. Any brass made in Europe prior to that was (I think) made using calamine. As I say, it was a common alloy in the very early medieval period but what happens post 8th century I couldn't say. The reason why 'copper alloy' became common terminology for archaeologists rather than 'bronze' was because analysis of artifacts revealed that copper/zinc alloy items were at least as common as copper/ltin alloys.


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Re: Brass!

Postby sally » Wed Oct 24, 2012 12:37 pm

Just to add to what Matt has already said, whilst you read up on this, you may also find copper alloys referred to as 'latten' in medieval sources.



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Re: Brass!

Postby Colin Middleton » Wed Oct 24, 2012 12:40 pm

IIRC from the MoL book (Dress Accessories, I think), there is a materials triangle diagram in the introduction which explans that most of the 'copper alloy' items were made of latten, which is a mix of copper, zinc and tin. However, the ratios of each are vary variable, so while everything sits in that triangle, where it sits will vary and any given item is unlikly to be brass or bronze as we think of them today, but nearer or further to one of them or the other.

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Re: Brass!

Postby Dave B » Wed Oct 24, 2012 12:57 pm

That's right Colin, there is an excellent paper in one of the museum of london books (I thought it was the household artifacts book, but I could be wrong, I have both).

Copper alloys had many different compositions, with varying amounts of Tin, Zinc, and other metals (IIRC lead was not uncommon).

Zinc could not be extracted as a pure metal, but was added by adding powdered Calomine ore to the crucible, which transferred the zinc, leaving the rocky bits behind on the bottom.

Charles, if you need something more definitibe, send me a PM, and if I get the chance I'll scan in the paper and send it to you

http://www.amazon.co.uk/Medieval-Househ ... 1843835436


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Re: Brass!

Postby Colin Middleton » Wed Oct 24, 2012 1:20 pm

You could be right Dave. I don't have Household Items yet, so that's not the bit that I'm thinking of, but there might be a better one in there that I don't know about.


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Re: Brass!

Postby guthrie » Wed Oct 24, 2012 1:38 pm

Charles13 wrote:I have a query about the use of brass in the medieval period. Many people in the reenactment world use brass objects for a whole range of uses: pins, rivets, buckles etc. However I have been told that 'no they didnt have brass as there wasnt a source of zinc'! Is this true? Its annoying as many finds are simply called copper alloy, without giving any indications of the makeup of said alloy. Should we only be using bronze? I'm only aware of brass and bronze as copper alloys in the broadest sense.

Ahem.
Speaking as someone whose done a fair bit of research on this sort of thing, and a 3 or 5,000 word essay on certain things to do with brass...

As Matt says, it depends on which part of the medieval period you are talking about regarding its use.
Moreover, the word bronze is comparatively recent. Thus in wills and letters and everything else in the medieval period you find mention of 'brass pots', meaning leaded antimony bronze by our nomenclature. Latten is the term more generally used to refer to what we call brass.

The method of making brass by adding zinc to copper is only 3 or 400 years old. Brass arose in the middle east, when they started adding this white powdery stuff scraped from furnace chimneys to metal (The zinc oxides that Matt mentioned). It was adopted rapidly by the Roman army and it's probably their fault it is so widely known. Thus from the first century BC onwards it became very popular all across Europe.
After the western Roman Empire fell, its production and use probably decreased, although I don't know much about that. But by the 8th century AD they were using sources of zinc ores in Germany, even making huge brass doors. Thus it was common enough in the early medieval period, albeit more expensive.
By the high medieval period it was defintiely being used to make all sorts of huge impressive items, from lecterns to those things you put water in to pour out for people to wash their hands with. Anything which could be made better by using a gold coloured alloy. Huge amounts of Dinanderie, so called after the town of Dinant, were being imported into England in the 1300's. It was mostly brass, made using the local ores.

The term 'copper alloy' is probably used because you can easily tell that something has copper in it, but it takes proper analysis to tell what mixture of other metals are in it. And until you do that analysis, all you know is that it is copper alloy. And as Matt wrote, not all things were bronze, there was brass as well hence the broader term is better.

For the manufacturing process of brass, see here for doing it at home:
http://calcinations.livejournal.com/158510.html
Or this proper academic paper:
http://www.ucl.ac.uk/archaeology/people/staff/martinon_torres/usercontent_profile/Martinon-Torres_Historical_Metallurgy_brass_2002.pdf
Marvel at the advanced technology being used in 16th century Germany, and the huge amount of brass they could produce.
And this for an old but still good book which should be bought by anyone interested in later (12th C onwards) English industries and crafts:
http://books.google.co.uk/books?id=mxjCN8R4pgsC&pg=PA81&lpg=PA81&dq=medieval+cementation+brass&source=bl&ots=VaFOj7fm4y&sig=AKGs0wcyTSao7lZTNYmSVROK8KY&hl=en&sa=X&ei=zOCHUOrqOIWA0AWE_oHgBA&ved=0CEwQ6AEwBzgK#v=onepage&q=medieval%20cementation%20brass&f=false

So you can tell this person that they're completely wrong in every way!



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Re: Brass!

Postby Charles13 » Wed Oct 24, 2012 2:25 pm

Well thankyou everyone, that has cleared things a little, I knew that matallic zinc wasnt available but just thought it unlikely they had no ore, especially as one of you said it occurs natrally with copper ores occasionally. It would still be nice if archeologists occasionally did some analysis of some more interesting finds - if only to work out production methods, lots of cheap chemical tests (ok bit distructive) or the old edax ones if youve access to an SEM. But I suppose thats the scientist in me getting annoyed! Again thankyou for your help. Oh and to clear things up I'm mainly thinking about late 15th century, although I do early 13th as well!



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Re: Brass!

Postby guthrie » Wed Oct 24, 2012 2:39 pm

Charles13 wrote:Well thankyou everyone, that has cleared things a little, I knew that matallic zinc wasnt available but just thought it unlikely they had no ore, especially as one of you said it occurs natrally with copper ores occasionally. It would still be nice if archeologists occasionally did some analysis of some more interesting finds - if only to work out production methods, lots of cheap chemical tests (ok bit distructive) or the old edax ones if youve access to an SEM. But I suppose thats the scientist in me getting annoyed! Again thankyou for your help. Oh and to clear things up I'm mainly thinking about late 15th century, although I do early 13th as well!

Archaeologists are limited by funding and time. Annoyingly so.
You know that the older tests are destructive; they did quite a lot of analyses over the 20th century, but the results are in journals and books, see for instance the one I recommended. Moreover alloys like bronze often have a certain amount of partition of elements, so getting a representative sample is quite hard and they ran into that problem quite a few times.
The thing about SEM's is that they require small samples and careful preparation. I have an MSc in Technology and Analysis of Archaeological MAterials, but there aren't many PhD's in that area going, otherwise I'd be happy in a basement somewhere with the SEMs.

What we do have nowadays are XRF's, a comparatively modern, non-destructive technology. But for the accurate bigger ones you have to get the sample arranged so that you get a good surface etc. Even better are hand held XRF's, the problem is of course funding and access etc. I did get to use a hand held XRF to find that graphitic clay crucibles from Dubrovnik (made in Germany) had been used to melt only copper, which was a very odd thing to find. No trace of zinc or tin or lead. Usually they are present a great deal on crucibles due to their volatility, but it seems the foundrymen wanted pure copper.

Lots more information is found in the Journals of the Historical Metallurgy Society. As re-enactors, I think we can act as the conduits between the academic sources of information and the public.



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Re: Brass!

Postby guthrie » Wed Oct 24, 2012 11:11 pm

Oh yes, production methods. What do you want to know about the production of in the 13th through 15th centuries? I can tell you, from my own experience and the various articles and books I have that were written by archaeologists and historians.

Even better, if you know a film crew and money, we could replicate the production methods. Don't you want to see a full scale bell casting furnace in operation?



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Re: Brass!

Postby kate/bob » Thu Oct 25, 2012 12:33 pm

I do! (sadly I have no money!)



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Re: Brass!

Postby Dave B » Thu Oct 25, 2012 7:15 pm

OK, I've dug out the textbooks, there are good papers in two of the MOL books. lots of tables of metalurgical analysis of finds from london dated 1150 - 1450.

The long and the short seems to be:
They had alloys that we would classify as brass
They had alloys that we would classify as bronze
they had alloys with both Zinc and tin
Lead was a very common component.
Alloys with significant Zinc (brass and leaded brass) were more common than alloys with significant tin (bronze and leaded bronze

I have scanned in the papers. I won't post them here due to copyright, but if anyone wants them PM me, I'll park them on the web and give you a link.

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Re: Brass!

Postby Hobbitstomper » Fri Oct 26, 2012 7:01 am

I think the Indians might have been able to make zinc a lot earlier than any commercial process in the West. However, pure zinc is useless in a medieval environment. It is softer than iron or bronze and harder to cast with than tin or lead. If you mess abut with it, you might get poisoned.

General rule from looking at metal analyses: Viking and Saxon is low/no zinc bronze. Norman onwards and it switches over to brass.



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Re: Brass!

Postby guthrie » Fri Oct 26, 2012 11:29 am

Here's a paper of analyses of early Saxon cruciform brooches. Some were decent brasses with high zinc, more were low zinc higher tin as you say:
http://archaeologydataservice.ac.uk/catalogue/adsdata/arch-769-1/dissemination/pdf/vol35/35_104_107.pdf



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Re: Brass!

Postby Medicus Matt » Fri Oct 26, 2012 1:25 pm

guthrie wrote:Here's a paper of analyses of early Saxon cruciform brooches. Some were decent brasses with high zinc, more were low zinc higher tin as you say:
http://archaeologydataservice.ac.uk/catalogue/adsdata/arch-769-1/dissemination/pdf/vol35/35_104_107.pdf


I was going to say 'Cobblers' to Andy's statement about Saxon stuff being low/no zinc but then thought perhaps he was referring to mid and late Saxon rather than early Saxon material. Early stuff features a lot of hi zinc content items as well as high tin content but, as time went on, zinc proportion decreases as the same Roman alloys are re-recycled (do you get a higher rate of zinc loss than tin loss when re-melting and casting I wonder?), presumably because tin was always available to add whereas zinc was not.

Mortimer's stuff is worth reading:-
http://ads.ahds.ac.uk/catalogue/adsdata/arch-810-1/dissemination/pdf/Archive_Mortimer_copper_alloy_composition_07.pdf
As is Brownsword's.


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Re: Brass!

Postby guthrie » Fri Oct 26, 2012 2:15 pm

Yes, I have much of Brownswords, although its later medieval.
Interestingly re. recycling, you have a related thing with enamel - was it in Theophilus? I can't find it - which was that the best glass to use for it was old Roman glass.

AS for tin and zinc, I don't have anything handy to prove it but what i have read and experienced myself is that yes, zinc evaporates more readily when liquid, although it does have a higher melting point. I could be wrong though, it isn't an area I have researched much and my library isn't quite detailed enough yet.




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