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
Etching of slags. Time: 30 sec. Etching solution Fay alite "A" "B" silicate "C" silicate eutectics FeO NaOH of 10% not etching not etching not etching not etching not etching Hydrochloric FeCl 3 5 gofFeCl 3 30 ml ofcc.HCl 120mlofH 2 O not etching not etcliing etching if dark coloured not etching not etching 1:1 of cold HCl slightly etching etching etching etching etching 1:1 of warm H 2 S0 4 strongly etching etching etching etcliing etching Note: When etching with FeCl 3 , the "B" silicate, which appears as a filling of the fay alite needle crystals, is etched much more strongly than the lamellar "B" silicate. One part of the slag melted during this treatment and the other part did not. The most interesting ones in respect of the investigation were those that did not become molten. The reduction of wiistite (FeO) was initiated at 1100 °C partly on the edges of larger grains, but in some grains it began in the internal regions, and in the dendrites rather in the region of dendrites — it started in an inconstant distribution, see Photos 6 and 7 (N = 600x and N = 200x in unetched status, in slags Nos. 2 and 18). At 1200 °C the wiistite had completely reduced. At 1200 °C the vitreous silicates had partly recrystallized and decomposed into darker and lighter components, and from the darker grey vitreous region, particularly close to the surface, a small quantity of metallic iron was reduced (Photo 8; N = 200x, unetched status, slag No. 10). Fayalite was not reduced, nor was the "B"-type silicate reduced from the slags of greater MnO content (Nos. 10,11). The metallic iron presented itself in uniform distribution in the molten slags (Photo 9; N = 200x, unetched status, slag No. 2). It is generally a ferrite, but because of the taking up of C, it developed into ledeburite. In a part of the non-molten slags, e . g. in Nos. 1,4,5,8,9 and 13, the formation of sponge iron commenced (Photo 10; N = 200x, unetched status, slag No. 1). In some cases the sponge iron is formed at the place of the "C" silicate-wüstite eutectics, and the little iron grains coalesced within a delimited area. In other slags the sponge iron develops on the boundary of the "B" -type silicate and seems to grow to the detriment of that. It is difficult to explain the developing of iron sponge in the softened but not molten slag because of the occurrence of such a slag (e. g. No. 9) in which the iron maintained the shape of the wiistite grains, but in some places started, to a small extent, the formation of iron sponge, too. On the basis of the changes observed in the slags subjected to reducing heat treatments at 1200 °C, they can be classified into three groups: 1. reducible slags: Nos. 1,4,5,8,13,18 2. hardly reducible slags: Nos. 2,3,6,9,10,12,16,17 3. not reducible slags: Nos. 7,11,14,15
