01-22-2009, 11:28 AM
Quote:If you see some roman items with an extraordinary degree of preservation, that even have the original colour, you can see often a yellowish/golden colour. That's closer to our today's brasses than to our today's bronzes, that are more "red" or "copper" coloured.
Roman uses a lot of copper alloys. Sometimes, they have a lot of items for reciclyng, so the final result often was a alloy with a lot of components.
And for some purposes, they add some metals to the alloys. Lead, silver, etc were added to the alloy. That metals were added to change aspects as the viscosity, point of melting, hardness, colour, etc.
The well preserved artefacts that have a golden colour are most likely water and marsh finds. The golden colour cupric alloys get in such a burial context is called a marsh patina. It's an all different story if they are preserved in another context (they won't be golden coloured then).
Like the others said, a lot of recycling was done so a lot of different alloys were used.
The Romans did not make brass but mined an ore called aurichalcum/orichalcum ("golden copper"). In this ore copper alloyed with zinc was present. Adding zinc to copper is a proces that was known probably in Afganistan and perhaps in India, but the Romans most likely did not do this, they just used the natural alloy orichalcum. Brass was often used for military equipment in the Imperial age.
The Romans used alloys with a high copper content and low zinc content to make things like rivets (this alloy is softer and better suited for rivetting than an alloy with a high zinc content). This alloy with a high copper content can be substituted by copper when you make e reconstruction. The appearance is the same.
Most Roman brass also seems to have a lower zinc content than our brass and would have been a bit less yellow than our brass.
I think there is info about this subject in the Lorica Segmentata books by Bishop, you can read the books online here: http://www.armatura.co.uk/
Oh and by the way: in most circumstances archaeological cupric alloys with a high tin content are very well preserved compared to alloys with a lower tin content.
Vale,
