M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)

Analysis - HEGEDŰS Zoltán: Conclusions of metallographic tests on the production methods of bronze articles and slags

HEGEDŰS Zoltán* CONCLUSIONS OF METALLOGRAPHIC TESTS ON THE PRODUCTION METHODS OF BRONZE ARTICLES AND SLAGS Abstract - As a result ofmetallographical tests, metallic iron was found in slags dating from the times of the Bronze Age, and tin-ore in bronze slags dating from the Middle Age

, Their origin and the possibilities of tin-ore application are discussed. Metallographic testing enables iron slags from ancient and mediaevei iron smelters to be demonstrated, showing the structural elements, the possibilities of their identifying and. further, details of the slag re ducibili ty. The metallographic testing of slags is not a simple job since besides the metal and non-translucent oxides and remainders of ores there are also crystalline and glassy components present. Interesting and often important information can be obtained from the slags of archaeological findings by combined metallographic, microscopic, or possibly by pétrographie methods, and an example for that should be the investigation of bronze and iron slags - as outlined in the following. Slags of Kisvarsány dating from the Bronze Age A bronze finding consisting of 19 pieces came to light in Kisvarsány from the "Ópályi B IV b" level of the Bronze Age [1]. Here we give the chemical composition rated upon oxides of the slag, which was found together

r

with the bronze articles: Fe

2 O3 = 5.4 mass%; Si0

2 = 72.0 mass% CaO = 1.4 mass%

; Al

2 0

3 = 16.4 mass%, and in addition, in small and undetermined quantities Ti, Zr and Mg were verifiable. The microscopic structure of the slag was the following: metallic iron inclusions and sferoidal, dendritic or net-like ordered Wiistite base (FeO) in a silicate .base. The presence of metallic iron in slags from the Bronze Age is a rare but not unknown occurrence. In his work reviewing the development of copper melting, in the part discussing the smelting of sulphide ores, Wer time [2] refers to the fact that one of the greatest anomalies of the period between 2000 and 1600 B. C. is the presence of metallic iron in copper metallurgical slags. In the copper slags excavated in Cyprus from the period between 2000 and 1600 B. C, metallic iron has been found in quantities of 29-37 mass%, but also in the copper metallurgical slags from Timna (Israel), dating back to near the same age, metallic iron has been found in smaller quantities. The development stages of metallurgy — according to Wertime - are as follows : — melting of native copper — use of slag-forming additives — smelting of easily reducible (oxidic

, carbonate) ores — smelting of polymetallic ores (sulphides) — production of arsenical bronzes — making of tin bronzes. *H-1111 Budapest, Lágymányosi út 26.