Giannis vs Polinik on the color of bronze :)

[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