Analizy metaloznawcze wybranych przedmiotów brązowych i ołowianych z cmentarzyska w Świbiu / Metallographic analyses of selected bronze and lead artefacts from the cemetery at Świbie

A comprehensive programme of archaeometric research into the chemical composition and manufacturing technology of Early Iron Age artefacts discovered in Świbie, Upper Silesia, has yielded a number of detailed observations and findings. Sixty-six artefacts from a collection of several hundred large bronzes were targeted for study. Energy dispersive X-ray fluorescence spectroscopy and scanning electron microscopy with micro-area composition analysis were used. In selected cases, non-destructive analysis was carried out by digital X-ray radiography. The study was preceded by macroscopic observation of the artefacts. It was shown that most of the large ring ornaments were made from castings subsequently subjected to numerous forging (reforging and shaping) and finishing treatments. Some of the wares, such as the massive ankle rings, retained many of the characteristics of the original cast, indicating that the finishing treatment was only applied when necessary due to the nature of the product (e.g. visual qualities). Decoration was applied using various techniques, often used in combination with each other (e.g. designing a decoration on a wax model and correcting it on the finished product). It was demonstrated that the characteristic constrictions found on the inside of the massive twisted-bar ankle rings of the Upper Silesia and Sącz (Stary Sącz) types could not be the effect of wear and tear, but evidence of intentional reforging, most likely aimed at creating a place to attach an organic strap to fix the ornament in place on the leg. The research has also identified a new category of imports from the circum-Alpine or Mediterranean areas, namely necklaces with a hooked clasp. The extraordinarily precise ornamental technique observed on the necklace, long known in the literature, from grave 102 (in which other imported luxury goods were also found), required the use of a tool in the type of a tap or a threader, and it has never before been identified in an Early Iron Age context in Poland. Above all, however, these studies made it possible to answer the research questions regarding the sample. The first question concerned the raw material and technological variation of the collection across functional and stylistic categories: Did the objects produced and/or used by the population using the cemetery differ in chemical composition of the alloy and manufacturing technique according to function or style? Although the raw material composition was quite similar for the majority of the artefacts (classic Cu-Sn tin bronze), it emerged that some of them had a slightly different composition, most notably an elevated lead content (above 1.5%, exceptionally up to 9.5%), and that this was not coincidental. More often than not, these objects, such as the necklace from grave 217 or the openwork knife handle fitting from grave 495, demanded castings that, due to their small thickness in the mould, required a special alloy with improved castability. This was not required with massive bronzes or those meant for forging sheet metal for the production of coiled ornaments ; these wares are usually characterised by a low proportion of intentionally added lead as an alloying component. No such consistency can be seen in the manufacture of small ornaments such as buttons or spiral pendants, presumably produced on a day-to-day basis from currently available raw material or from recycled raw material. A satisfactory answer was also obtained to the second main question: Whether it was practised to furnish the deceased with sets uniform in style and raw material (possibly including objects produced especially for the funerary ceremony), or whether the objects amassed in the grave were made from raw material from different sources and at different stages of the buried person’s life. Proceeding from a comparison of all the bronzes from three rich burials (graves 102, N=11; 124, N=12; 574, N=9), it was concluded that they were certainly not furnished with complete ceremonial costumes prepared by one workshop, from one batch of raw material. The only objects that they can be considered sets in terms of both style and workshop are pairs of large bronzes (such as ankle rings or massive bracelets), which were most often made from a homogeneous raw material and probably functioned together from manufacture to deposition in the grave. In the group of small bronzes, this contextual approach (as well as the functional one) confirmed a greater range of raw material patterns.