Giannis vs Polinik on the color of bronze :)

[PMBardunias]

Perhaps one of you can tell me why ??? ?????? ?????? at Xenophon (Const. Lac. 11.3) is translated as Brass and not bronze.

The section in english:

[3] In the equipment that he devised for the troops in battle he included a red cloak, because he believed this garment to have least resemblance to women's clothing and to be most suitable for war, and a brass shield, because it is very soon polished and tarnishes very slowly.

[Paullus Scipio]

Matt wrote:

I used to think the same thing, but Jeroen Zuiderwijk (another recognized expert bronze caster) has recently done some smelting.......Granted, there could be a big difference in ore types and quality, charcoal quality, furnace efficiency, etc. So where did we get those bigger numbers?

Most interesting, Matt - even given the differences you refer to, one would not expect a factor of ten difference in amount of fuel (Jeroen used roughly the same amounts of ore and fuel by weight 10kg of ore + 8 kg of charcoal to produce 3-4 kg of copper). Perhaps when attempting smelting on a larger scale, the efficiency drops......Also, it sounds like a very different grade of ore - far less pure - was referred to because 30 kg of sulfide ore only produced 1 kg of copper ( Jeroen got 4kg or so of copper from 10 kg of malachite) and that, I think, would account for a lot.....Jeroen evidently started with 'copper rich' ore (malachite, which is a corroded form of fairly pure copper).Notice that again a factor of roughly ten is involved..... It is quite possible both sets of figures are accurate in different circumstances, and notice that the very large quantities of fuel quoted apply "especially if the ore is dominantly sulfide".

John wrote:

I have always understood as others have said that the colour comes down to the exact alloy of copper used, and that zinc gives a more yellow brass-like colour compared to tin which gives a redder colour. I also have been given to believe that copper/zinc is something we find in the Italy and the west (Roman) while copper/tin is more Hellenistic and eastern.

....and Gregory wrote:

I have always understood as others have said that the colour comes down to the exact alloy of copper used, and that zinc gives a more yellow brass-like colour compared to tin which gives a redder colour. I also have been given to believe that copper/zinc is something we find in the Italy and the west (Roman) while copper/tin is more Hellenistic and eastern.

You'll notice I qualified my statements, and was using a generalisation - one would expect some variation depending on the type of ore used, and whether the bronze had a low (5%) or high(15%) tin content. The point I was trying to make was that by and large, ancient bronze looked more like brass than modern 'red' bronze......and it does !! The fact that there is colour variation e.g. from 'gold/yellow with a pink tinge' to 'gold/yellow with a brassy greenish tinge' or 'gold/yellow with a pale silvery/white tinge' does not negate this.....ancient bronzes, as many of the photos on this thread show, are hues of 'gold' not hues of 'red', or 'green' - unless a patina has been allowed to develop [digression: the presence of verdigris is a sure -fire pointer to a probable fake!] or 'grey'

Christian wrote:

Paul,
1. please look, e.g., at the metallurgical analysis of finds at Haltern or Kempten. What you say is not true.
You'll need to elaborate on which part you consider incorrect/'not true'. Phosphor bronze certainly didn't exist in ancient times. It is also true that ancient copper alloys were different to modern ones - so much so that metallurgical analysis allows easy detection of the many 'fakes' and 'pastiche' helmets foisted on collectors in the 19th and early 20th centuries. Even Brass is different - for example, Roman brass never exceeded 30% zinc content, while from the seventeenth century onward brass typically has a zinc content of 35% or more.
2. ancient bronze can not be distinguished from brass when there is a patina on it. That´s why the museums label "copper alloy", when there is no metallurgical analysis. Good publications try to find out the difference with metallurgical analysis (Haltern again, e.g.)
Agreed!....but it is also true that a typical bronze Greek or Roman helmet for example, with a tin content from 8-9% - such as is typical of a Corinthian - or 7-8% as is typical of a Montefortino, have a 'golden' appearance when new and polished that is all but indistinguishable from brass - the Munich helmet being a case in point, with not even a hint of 'pink' or 'red'.
3. removing patina does not necessarily show the original colour. When in ground or in water e.g. the tin may "move" towards the surface of the metal over time, resulting in a different colour on the surface than the one it originally had. Same can happen when heating a metal. If you want to see the original colour, you need to know the alloy and re-make it.
Also agreed!....It can be difficult to determine original colour without reproducing the particular alloy, because of changes over time....

The "yellow" helmet from munich / sicily looks in natural light like this:
Thanks for publishing these photos, which literally show the helmet in a different light ! :wink: Most interesting. However, even in those photos and despite the patina it is clear that the helmet is of a 'golden' or 'brassy' hue, not a 'reddish' or 'greenish' hue.....which is my whole point.

I don't think you will find us in disagreement here - I was merely enlarging and expanding on the points you made, Christian.
Dan wrote:

I have to agree. It is very easy to tell the difference between a copper-tin alloy and a copper-zinc alloy if they are new-cast and polished. There is more red in the tin alloy. It is a "warmer" colour. I tend to see a "greenish" hue in bass. As has been said, once they develop a patina and/or have been buried for a long time, you need metallurgical analysis to tell them apart.

Again, I don't disagree, it is possible to tell some 'bronzes', particularly modern ones ( and significantly, all the 'pinkish' hued examples here are modern reproductions), from brass with the naked eye, but in many/most instances ( and evidently depending on light conditions too!) ancient bronze artifacts had a 'golden hue' that was all but impossible to distinguish from ancient brass with the naked eye, and in general, ancient bronze was of a 'golden' colour very unlike the 'coppery/red' of modern bronze alloys, as can be seen from the photos posted in this thread, especially the Munich helmet ( and accompanying greaves, by the way) and the cast objects....... In simple terms, a layman looking at the Munich helmet/greaves, despite lighting conditions or changes wrought by time, would say it was made of 'brass' not 'bronze'.

[Paullus Scipio]

Perhaps one of you can tell me why ??? ?????? ?????? at Xenophon (Const. Lac. 11.3) is translated as Brass and not bronze.

The section in english:

[3] In the equipment that he devised for the troops in battle he included a red cloak, because he believed this garment to have least resemblance to women's clothing and to be most suitable for war, and a brass shield, because it is very soon polished and tarnishes very slowly.

'chalkou' is translated in the lexicons as "of copper, bronze, or brazen ( lit in English; made of brass)".......'brazen aspides' naturally translates as brass....

Perhaps a better translation might be 'copper alloy' since, as I mentioned in previous posts, ancient bronzes and modern bronzes are not the same, and even Roman brass is not the same as modern brass.......

[PMBardunias]

'brazen aspides' naturally translates as brass....

I guess what I am asking is, is there any reason to expect a zinc rather than tin alloy for Spartan shield facings?

[caiusbeerquitius]

Christian wrote:

Paul,
1. please look, e.g., at the metallurgical analysis of finds at Haltern or Kempten. What you say is not true.
You'll need to elaborate on which part you consider incorrect/'not true'. Phosphor bronze certainly didn't exist in ancient times. It is also true that ancient copper alloys were different to modern ones - so much so that metallurgical analysis allows easy detection of the many 'fakes' and 'pastiche' helmets foisted on collectors in the 19th and early 20th centuries. Even Brass is different - for example, Roman brass never exceeded 30% zinc content, while from the seventeenth century onward brass typically has a zinc content of 35% or more.
2. ancient bronze can not be distinguished from brass when there is a patina on it. That´s why the museums label "copper alloy", when there is no metallurgical analysis. Good publications try to find out the difference with metallurgical analysis (Haltern again, e.g.)
Agreed!....but it is also true that a typical bronze Greek or Roman helmet for example, with a tin content from 8-9% - such as is typical of a Corinthian - or 7-8% as is typical of a Montefortino, have a 'golden' appearance when new and polished that is all but indistinguishable from brass - the Munich helmet being a case in point, with not even a hint of 'pink' or 'red'.
3. removing patina does not necessarily show the original colour. When in ground or in water e.g. the tin may "move" towards the surface of the metal over time, resulting in a different colour on the surface than the one it originally had. Same can happen when heating a metal. If you want to see the original colour, you need to know the alloy and re-make it.
Also agreed!....It can be difficult to determine original colour without reproducing the particular alloy, because of changes over time....

The "yellow" helmet from munich / sicily looks in natural light like this:
Thanks for publishing these photos, which literally show the helmet in a different light ! :wink: Most interesting. However, even in those photos and despite the patina it is clear that the helmet is of a 'golden' or 'brassy' hue, not a 'reddish' or 'greenish' hue.....which is my whole point.

I don't think you will find us in disagreement here - I was merely enlarging and expanding on the points you made, Christian.

Dear Paul,
1. modern phosphor bronze normally doesn´t have more than 0,5% phosphor in it, this doesn´t really have an effect on the colour. Indeed Phosphor bronze didn´t exist. Arsenic bronze did. To elaborate: You said modern reddish bronzes did not exist". This is not true in regard of the colour, as that is what you are talking about. Of course modern bronzes did not exist, they are too "pure". In regard of colour this is wrong, though. A look at the metallurgical part of the Haltern publication quickly shows this.
e.g.: #385
Cu 91,33
Sn 7,01
Pb 1,37
Zn 0,02
Fe 0,05
Ni 0,04
Ag 0,06
Sb 0,10
As <0,10
Optically this would not be distinguishable from a modern CuSn8 bronze.

@ the helmet:I mixed up the metals above the brow guard is brass, the skull bronze... ^^

2.: No, I disagree. Bronze with a tin content of below 10% will always have a copperish tone, unless you also add a good amount of Pb.

3.: The munich helmet (plus sauroter and greaves) should be first examined in different ways, before used like this in an argument. Was it exposed to a decomposing body? How was it restored? What chemicals were used in the restoration process? How long ago did the restoration take place? All these factors may have an impact on the colour of the helmet as we see it today. Note that until the 1920ies heating was also used for metal restoration, i.e. glowing out iron pieces or bronze / brass items. This of course would also have had an impact on the colour of the helmet...
Cheers! Christian

[Paullus Scipio]

Dear Paul,
1. modern phosphor bronze normally doesn´t have more than 0,5% phosphor in it, this doesn´t really have an effect on the colour. Indeed Phosphor bronze didn´t exist. Arsenic bronze did. To elaborate: You said modern reddish bronzes did not exist". This is not true in regard of the colour, as that is what you are talking about. Of course modern bronzes did not exist, they are too "pure". In regard of colour this is wrong, though. A look at the metallurgical part of the Haltern publication quickly shows this.
e.g.: #385
Cu 91,33
Sn 7,01
Pb 1,37
Zn 0,02
Fe 0,05
Ni 0,04
Ag 0,06
Sb 0,10
As <0,10
Optically this would not be distinguishable from a modern CuSn8 bronze.
Again we are not in disagreement - I was making a [i]generalisation, and pointing out that most ancient bronzes were originally 'yellowish' like brass rather than the 'reddish' hue of modern 'bronze'. Naturally, there are going to be particular items that don't fit the generalisation - the exceptions that 'prove' (i.e. test) the rule.......[/i]

@ the helmet:I mixed up the metals above the brow guard is brass, the skull bronze... ^^

2.: No, I disagree. Bronze with a tin content of below 10% will always have a copperish tone, unless you also add a good amount of Pb.
Well I'm certainly not going to quibble about the colour difference between "9%" and "10%" !!. For further differences, one could note the diferences in alloys used in early, middle and late corinthians. Perhaps we can agree that lower tin proportion would lead to a 'rosy' or 'pinkish' hue ( e.g. 7 C BC corinthians), while higher tin proportions typical of 'classical' or 'late' corinthians lead to a 'brassy' colour ???

3.: The munich helmet (plus sauroter and greaves) should be first examined in different ways, before used like this in an argument. Was it exposed to a decomposing body? How was it restored? What chemicals were used in the restoration process? How long ago did the restoration take place? All these factors may have an impact on the colour of the helmet as we see it today. Note that until the 1920ies heating was also used for metal restoration, i.e. glowing out iron pieces or bronze / brass items. This of course would also have had an impact on the colour of the helmet...
Cheers! Christian
Again, agreed! As I said earlier, colour changes can be wrought by time and restoration and one would have to reproduce the exact alloy to be certain of the original colour. Examination of other close-up photos of the Munich example reveals a subtle variety of colour hues - but the matters you describe wouldn't dramatically change the overall colour from 'coppery/red' to 'brassy/yellow. For our purposes, the particular hue is not too important, merely the fact that ancient bronze helmets such as the Munich and other 'bronze' examples were mostly of a 'gold/yellowish hue', rather than the 'reddish/coppery' colour we tend to associate with modern 'bronze'......

[Gaius Julius Caesar]

I had always understood the import of tin from Britain to produce bronze included the bronze used/made in Greece?
Is this also incorrect?

[Matthew Amt]

I guess what I am asking is, is there any reason to expect a zinc rather than tin alloy for Spartan shield facings?

Nope. It's just a translator running a little freely, is all. Same reason we get Goliath wearing a "coat of mail" (originally "thorax"), while things like "hamata" get translated as "breastplate"!

Matthew

[Paullus Scipio]

Gaius Julius Caesar wrote:
I had always understood the import of tin from Britain to produce bronze included the bronze used/made in Greece?
Is this also incorrect?

Tin was obviously of extreme importance for bronze making throughout ancient times, and it was imported long distances from known tin mining districts of antiquity, namely Erzgebirge along the border between Germany and Czech Republic, the Iberian Peninsula - the fabled Tartessus,( from before Assyrian times onward) Brittany in France (exploited mainly after the Roman conquest of Gaul), and Devon and Cornwall in southwestern England. Another minor source of tin is known to exist at Monte Valerio in Tuscany, Italy. This source was exploited by Etruscan miners around 800 BC, but it was not a significant source of tin for the rest of the Mediterranean. The Etruscans themselves found the need to import tin from the northwest of the Iberian Peninsula at that time, and later from Cornwall......Devon and Cornwall were important sources of tin for Europe and the Mediterranean throughout ancient times, but began dominating the market during late Roman times in the 3rd century AD with the exhaustion of many Spanish tin mines.......

Mining in Cornwall has existed from the early Bronze Age around 2150 BC. Cornwall was traditionally thought to have been visited by metal traders from the eastern Mediterranean.The Rillaton Cup and the Pelynt Dagger are two artifacts that have been found in Cornwall that show contact with the Mycenaean Greek world. However, later, it is likely that the tin trade with the Mediterranean was controlled by the Veneti across the channel, who traded it it on down through Southern France and the Mediterranean. Britain was one of the places proposed for the 'Cassiterides', that is Tin Islands.

As South-West Britain was one of the few parts of England to escape glaciation in the Ice Ages, tin ore was readily available on the surface. Originally it is likely that alluvial deposits in the gravels of streams were exploited but later underground working took place. Shallow cuttings were then used to extract ore.

Control of the tin trade to Eastern Mediterranean and Middle Eastern countries seems to have been in Phoenician hands and they kept their sources secret - but significantly by their control of the Pillars of Melquart/Herakles ( straits of Gibraltar) and colony at Gades/Cadiz, they controlled both Spanish/Tartessian and British sources. The Greeks understood that tin came from the 'Cassiterides', the "tin islands", of which the geographical identity is debated, but most likely refers to Devon and Cornwall. By 500 BC Hecataeus knew of islands beyond Gaul where tin was obtained. Pytheas of Massalia(Marseilles) travelled to Britain about 325 BC where he found a flourishing tin trade, according to the late report of his voyage. Posidonius referred to the tin trade with Britain around 90 BC but Strabo in about 18 AD did not list tin as one of Britain's main exports. This is likely to be because Rome was obtaining most of its tin from Spain at the time.

[caiusbeerquitius]

Dear Paul,
1. modern phosphor bronze normally doesn´t have more than 0,5% phosphor in it, this doesn´t really have an effect on the colour. Indeed Phosphor bronze didn´t exist. Arsenic bronze did. To elaborate: You said modern reddish bronzes did not exist". This is not true in regard of the colour, as that is what you are talking about. Of course modern bronzes did not exist, they are too "pure". In regard of colour this is wrong, though. A look at the metallurgical part of the Haltern publication quickly shows this.
e.g.: #385
Cu 91,33
Sn 7,01
Pb 1,37
Zn 0,02
Fe 0,05
Ni 0,04
Ag 0,06
Sb 0,10
As <0,10
Optically this would not be distinguishable from a modern CuSn8 bronze.
Again we are not in disagreement - I was making a [i]generalisation, and pointing out that most ancient bronzes were originally 'yellowish' like brass rather than the 'reddish' hue of modern 'bronze'. Naturally, there are going to be particular items that don't fit the generalisation - the exceptions that 'prove' (i.e. test) the rule.......[/i]

@ the helmet:I mixed up the metals above the brow guard is brass, the skull bronze... ^^

2.: No, I disagree. Bronze with a tin content of below 10% will always have a copperish tone, unless you also add a good amount of Pb.
Well I'm certainly not going to quibble about the colour difference between "9%" and "10%" !!. For further differences, one could note the diferences in alloys used in early, middle and late corinthians. Perhaps we can agree that lower tin proportion would lead to a 'rosy' or 'pinkish' hue ( e.g. 7 C BC corinthians), while higher tin proportions typical of 'classical' or 'late' corinthians lead to a 'brassy' colour ???

3.: The munich helmet (plus sauroter and greaves) should be first examined in different ways, before used like this in an argument. Was it exposed to a decomposing body? How was it restored? What chemicals were used in the restoration process? How long ago did the restoration take place? All these factors may have an impact on the colour of the helmet as we see it today. Note that until the 1920ies heating was also used for metal restoration, i.e. glowing out iron pieces or bronze / brass items. This of course would also have had an impact on the colour of the helmet...
Cheers! Christian
Again, agreed! As I said earlier, colour changes can be wrought by time and restoration and one would have to reproduce the exact alloy to be certain of the original colour. Examination of other close-up photos of the Munich example reveals a subtle variety of colour hues - but the matters you describe wouldn't dramatically change the overall colour from 'coppery/red' to 'brassy/yellow. For our purposes, the particular hue is not too important, merely the fact that ancient bronze helmets such as the Munich and other 'bronze' examples were mostly of a 'gold/yellowish hue', rather than the 'reddish/coppery' colour we tend to associate with modern 'bronze'......

Dear Paul,
1. well, you said the reddish bronze didn´t exist. That´s why I was arguing. However, items like Haltern #385 are not exceptions, they exist in large numbers (manly in pre-Caesarian context). I just took out one example from which I posted the complete met. analysis / alloy.

2. Basically yes, that would be what we would expect, but again there are not enough examples of which we have an analysis to back up such a statement.

3. Oh, I think this is important. You were using the helmet as an example for the hypothesis that there were many "yellowish" helmets, plus that the coppery bronzes are rather a modern thing. In fact all these factors I named may have indeed changed the bronze from a reddish to a yellowish tone. IIRC these things are discussed in detail in the publications of the bronzes of the Mahdia shipwreck. As I said above, to find out what colour there was originally, we need to re-cast the alloy. It doesn´t help to look at the item as it is now.

[nikolaos]

Folks,

How you polish and clean your metal also effects the appearance. Modern chemical (brasso) and gum abrasive (wheel) polishes polish the surface but do not leave a protective layer. Unless further treated it will corrode more quickly.

Historical polishing techniques use the abrasive in an oily base, which polishes and protects at the same time.

That said, polishing compound grit range with jewellers rouge at the finest end hasn't really changed all that much.

One practice that is far less common today is burnishing, where the surface of the metal is compressed into a higher polish by pressure from a harder work tool. It has a profound affect on appearance and can be performed on any historical metal. If you've every seen it, you'll know that nothing shines like burnished gold.

Have fun!
Cole

[M. Demetrius]

Polishing with abrasives makes increasingly smaller "grooves" from the grit, and gives an increasingly higher gloss, but microscopically, it will still be a rough surface. These grooves can be filled by dust, dirt, and other material, interfering with the gloss.

Burnishing flattens any of the high spots adjacent to the grooves left by abrasives, and gives a microscopically smoother surface. Hence, the object will have a shinier appearance, and less surface irregularities for impurities to enter, making a longer-lasting shine.

Polished then burnished metals will be very mirror-like.

[caiusbeerquitius]

It gets more confusing. I just checked a book on metallurgy. It states that
1. brass under 20% zinc normally has a brownish-reddish colour.
2. bronze under 20% tin normally has a brownish-reddish colour.

only when the proportion of copper goes below 80% the red / copper turns into a yellow tone, on both metals.
I cannot verify this empirically, since I never made alloys with over 10% tin, zink or lead, but all the ones I made were rather reddish / coppery when cast and cleaned.
However, I see no reason to question metallurgical tables, I assume those statements are correct. To me it perfectly makes sense in regard of my experience in mixing Roman alloys.

What does this mean, then? As far as we can see from the Haltern finds, where we have a metallurgical analysis for (I think) all items, only a small amount was actually in a yellowish tone. The question is, in the end: Weren´t many / most of these items tinned anyway?

And, following: Would a tinned surface on a helmet like the one from Sicily result in a yellowish colour nowadays? Hmmmm...

Besides:
In regard of low copper part in alloys, I think you forgot the mirror-bronzes in Antiquity, Paul. I just thought of them, and IIRC these often have below 70% copper.

See
Friedrich Tabellenbuch – Metall- und Maschinentechnik, (Troisdorf 2008).
C. J. B. Karsten, System der Metallurgie: geschichtlich, statistisch, theoretisch und technisch (Berlin 1831).

[M. Demetrius]

allOY VEY! :lol: Confusing, yes!

[caiusbeerquitius]

It really gets interesting in regard of reconstructions / reenactment. ^^

Let´s call this the "much-more-civilized-than-the-tunic-colour-debate-metal-colour-debate" (mmctttcdmcd)