12-22-2010, 03:24 PM
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).
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).
Christian K.
No reconstruendum => No reconstruction.
Ut desint vires, tamen est laudanda voluntas.
No reconstruendum => No reconstruction.
Ut desint vires, tamen est laudanda voluntas.
