Experience of Ultrasonic Use to Stabilize Archaeological Iron Artifacts with Active Corrosion

Of all the complex problems of museum storage of archaeological objects, iron objects represent one of the most difficult. In the process of corrosion, an iron object passes through several stages, from oxidation of the metal surface to full mineralization. The greatest problem consists of the items in the stages of oxidation, when the metal is almost completely corroded and converted into minerals. Mineral peels exfoliate under the influence of active corrosion, leading to a loss of historical significance of the object. In the world’s practice of archaeological iron conservation, there are several different ways of stabilization, but none of them can guarantee the integrity of the iron artifact during its museum storage. To date, the most effective conservation method of stabilizing archaeological iron is alkaline sulfite treatment. However, this method has a number of drawbacks, the main of which is the duration of the stabilizing treatment. The authors consider the possibility of increasing the efficiency of the method of processing archaeological iron objects in an alkaline sulfite solution by means of ultrasonic solution activation. In the course of the experimental study, it has been established that the use of ultrasonic in alkaline sulfite treatment hugely increases the efficiency of the method.

Cultural and Technological Characteristics of Russian Forged Iron Tools from the Selkup Cemetery Migalka in the Middle Ob Basin

This study addresses Russian iron artifacts from the Narym Selkup cemetery Migalka, dating to the late 1600s to early 1700s. Two most important categories of tools are described—knives and axes. In terms of morphology, knives fall into two groups: straight-backed and those with convex (“humped”) backs. The combination of a “humpbacked” blade, typical of native manufacture, and Russian hilt plates precludes an unambiguous ethnic attribution. Special attention is paid to knives with fi ligree-enamel hilt plates as markers of high socio-economic status. The garniture evidences northern Russian origin. The metallographic analysis of knives (22% of the sample) revealed two technological groups: made of solid steel and welded. Axes, made by Russian artisans, are of the shaft-hole type and fall into four types. The analysis, relating to 42% of the sample, indicates two techniques: welding of a steel blade onto an iron base or a piece of raw steel, and using irregularly carbonized metal for forging the entire axe. Ferrous metal items follow the Russian technological traditions. Three key factors accounted for the spread of Russian artifacts among the natives: “Tsar’s gift” for paying the yasak (tribute); colonization of Siberia followed by the emergence of trade manufacture; and the involvement of natives, specifi cally the Narym Selkups, in the all-Russian market. Our fi ndings attest to the relevance of iron artifacts from archaeological sites to the historical and cultural studies of the colonization period in western Siberia.

Mineralogical-Geochemical Study of Corroded Iron-Based Metals from a Salt Mine Environment

Metal fragments (pipe, chain, valves), at advanced stages of corrosion, were collected underground in the Wieliczka salt mine. Macroscopically distinct zones of corroded material, as well as black blisters on the surface of different metal fragments, were studied using scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Mössbauer spectroscopy (MS). SEM-EDS studies showed various morphological forms with different chemical compositions. The original outer zone of the iron artifacts is mainly composed of aggregates of needle-shaped goethite crystals with idiomorphic crystals of halite. A subsequent zone, toward the inner margin, is composed mainly of fine granular aggregates of magnetite. Goethite (α-FeOOH) and akaganeite (β-FeOOH) form spherical, fibrous, and structureless aggregates in the next internal zone. Forms of aggregates seem to depend on the chloride content, 1 wt% to 3.5 wt% Cl in the structureless aggregates and 5 wt% to 9 wt% Cl in the regular ones. In addition, in the internal zone crystals of lepidocrocite form rosettes. Blisters are built of the acicular akaganeite crystals, which form fibrous aggregates in the shell and spherical ones in the interior. The relative concentrations of iron bearing minerals in the studied zones, i.e., akaganeite, hematite, goethite, magnetite, and lepidocrocite are established. Where they dominate, the zones are: black (magnetite), orange (goethite, lepidocrocite, akaganeite), and light brown (goethite).

BLACKSMITH’S CRAFT OF THE POMORS IN THE CONTEXT OF RUSSIAN IRONWORKING

Дальние походы поморов в районы промыслов требовали наличия разнообразного инвентаря из железа и стали. Такой инвентарь широко представлен в коллекциях из раскопок поморских поселений на архипелаге Шпицберген. В результате археометаллографического исследования серии железных изделий установлено, что поморское кузнечное ремесло находилось в русле русской железообработки XVI XVII вв. Специфику поморского кузнечного ремесла можно видеть в изготовлении особых орудий, необходимых для ведения промысла. При этом наблюдается корреляция типа поковок и технологических схем их изготовления. Long distance expeditions of the Pomors to hunting areas required various types of gear made from iron and steel. Such implements and weapons are well represented in collections from excavations of Pomor settlements in the Spitsbergen (Svalbard) archipelago. The archaeometallographic study of a series of iron artifacts established that Pomor blacksmiths craft correlates well with the Russian ironworking trends of the 16th 17th centuries. Specific traits of the Pomor blacksmiths craft manifest themselves in production of special tools the Pomor needed to hunt animals and catch fish. At the same time correlation is established between the types of forged pieces and the sequence of production operations.

Interpreting 14C Measurements on 3rd–4th Century AD Iron Artifacts from Nydam, Denmark

ABSTRACTRadiocarbon (14C) ages were determined for 10 iron samples from the war booty offering site in the Nydam peat bog (SE Denmark), and compared to archaeologically inferred periods of deposition. Additional 14C measurements were carried out for modern iron standards made with charcoal of known isotopic composition to evaluate possible effects of handling. Modern iron standards give depleted 14C concentrations, compared to the initial charcoal 14C composition, and may indicate carbon fractionation effects during carbon dissolution in the iron lattice. Further studies are needed to verify if this is a common effect during iron production. 14C dating of two swords and one ax head are in comparatively good agreement with expected deposition times and indicate only small old-wood effects. In contrast, 14C dating of iron rivets from the Nydam (B) oak boat proved difficult due to corrosion with siderite (FeCO3) and conservation with wax. A step-combustion procedure was applied, using a low (∼570–600°C) temperature prior to the high (∼970–1000°C) combustion temperature for carbon extraction, aiming to remove siderite and wax before collecting the original carbon dissolved in the iron lattice. Nevertheless, measured 14C ages of the iron rivets differ by about 200–300 years from the dendro-date of the Nydam (B) oak boat they belong to, indicating persisting aging effects (e.g. old-wood, contamination with fossil carbon added during iron making and/or handling prior 14C dating). Also, a possible recycling of older iron cannot be excluded.

The Technological and Chronological Implication of 14C Concentrations in Carbon Samples Extracted from Mongolian Cast Iron Artifacts

ABSTRACTCast iron objects recovered primarily in eastern Mongolia, spanning the Xiongnu through the Early Historic periods (ca. 3rd BC–AD 17th century), were examined for their radiocarbon (14C) concentration and microstructure. Most of the samples examined were found to have originated from charcoal-based smelting with a few exceptions that were made using a mineral coal-based technique. A comparison of 14C dates with dates derived from artifact typology allowed the charcoal-smelted objects to be classified into two groups, based on whether the radiometric and typological periodization are in agreement or not. In addition, those with differing 14C and typological dates can be divided into two subgroups with and without evidence for a melt treatment applied after original casting. These conflicting dating results are confusing and would seem to provoke skepticism about the use of 14C measurements for dating iron artifacts. We demonstrate however that 14C analysis, when combined with metallographic examination and other lines of chronological evidence, can clarify the history of a given iron object and its multiple users, often separated in time by more than a millennium.