Hans Huisman

The use of Hand-Held XRF for investigating the composition and corrosion of Roman copper-alloyed artefacts

The study of archaeological artefacts using deployed in situ analytical instruments presents some obvious advantages. Including, obtaining an immediate feedback that can be used to redefine in real-time fieldwork strategies. Ideally analytical field instruments should also have characteristics that limit damage to the studied artefact.Here, we present a case study on the use of a Hand Held XRF (HH XRF) device employed to define the composition of copper-alloyed artefacts retrieved from the Roman military site of Fectio in the vicinity of Vechten (The Netherlands). The goals of the study were to establish artefact preservation status, to investigate artefact elemental composition, and to compare the composition of artefact corrosion layer and uncorroded core.The results showed that the objects were in an overall good preservation state. Decuprification and dezincification represented the probable main corrosion processes resulting in the formation of smooth corrosion layers or patinas. The major elemental composition of the artefacts’ uncorroded cores showed a wide-range variability most likely associated with recycling practices of scrap metal during the 3rd century CE.

Tools for Predicting Damage to Archaeological Sites Caused by One-Dimensional Loading

Tools are developed to predict damage to archaeological remains caused by the construction of line infrastructure on soft soil. They are based on numerical modelling and laboratory testing supported by X-ray microcomputed tomographic observations, and micromorphological analyses of thin sections. They have been validated for one-dimensional (1D) loading at two sites in the Netherlands where soil has been placed on top of organic layers rich in ecofacts and overlaying Pleistocene sands. Numerical prediction of the deformation of soft layers underneath an embankment remains a challenge for geo-technical engineers. Errors on surface settlement prediction reach ±15% of the measured total settlement. Laboratory observations show that vulnerable artefacts can get crushed when packed loosely in pure assemblies under 1D loading equivalent to less than 5 m of sand. Fragmentation is assimilated to loss of archaeological value as it compromises recovery during sieving. Embedment in a sandy or a very compressible organic matrix has a beneficial effect on the resistance of ecofacts. Embedded ecofacts can resist a load of more than 12 m of sand. Flattening and re-orientation of soft plant remains occur during 1D loading without microscopic damage of tissues.

Relax, Don’t Do It: A Future for Archaeological Monitoring

Preservation in situ and the monitoring of archaeological sites have become important themes since the acceptance and implementation of the Valletta Treaty. In the last few decades, our knowledge of degradation processes has increased manyfold, and a range of techniques have been tested and applied for use in both assessment and monitoring. Despite these successes, all is not well. First, we have little notion of the speed of the decay processes involved. This makes it difficult to distinguish between acute and protracted degradation. Apart from that, many assessments and subsequent monitoring projects rely (too?) heavily on complex and costly specialist technology. For any future preservation — in situ — projects low-tech observations together with best estimates of decay rates and archaeological site information should be combined to make an accurate assessment of the effects of decay on the archaeological record. Monitoring for preservation purposes is only appropriate if (1) decay processes occur within a relevant and measurable time scale, and (2) if mitigating actions can be taken or preservation ex situ can be performed (i.e. a rescue excavation) if significant degradation takes place.

A Qualitative Approach for Assessment of the Burial Environment by Interpreting Soil Characteristics; A Necessity for Archaeological Monitoring

Abstract Modern-day archaeological monitoring is often hampered by lack of money, lack of time, inadequate measuring equipment, and lack of insight in the conservation potential of a site. Although in modern archaeological excavations soil characteristics are noted (colour, texture, groundwater level, and sometimes mineralogy), these characteristics are mainly used for the interpretation of a site. However, by looking to these characteristics from a conservational view eventually combined with the conservation status of the archaeological objects, much can be learned about the burial environment. This is essential for optimizing archaeological monitoring. Degradation processes result from the change of reactive phases in the soil or the site. Reactive phases are soil components such as organic matter, sulfides, iron(hydr)oxides and carbonates (chalk, shells), and, if present, components in the ground or interstitial water such as hydrogen ions and sulphate. The presence of these phases can easily be established by the archaeologist or soil scientist in the field. We propose a simple field-based method for assessing degradation processes essential for in situ preservation and monitoring.

Early Roman copper-alloy brooch production: a compositional analysis of 400 brooches from Germania Inferior

We present here a compositional study of a large number of copper-alloy brooches, undertaken in 2014 using Handheld X-ray Fluorescence Spectrometry (HHpXRF). The brooches, which come from the area of Nijmegen, date from the Late Iron Age until the 2nd c. A.D. Our aim is to explore the ways in which artefact production was organized both in the context of Roman centres and in the countryside. The link between alloys and workshop organization will be elucidated before the methodology and results are presented. The results will then be discussed, leading to the formation of several hypotheses regarding the organization of workshops that produced metal artefacts. Scientific interest in the composition of ancient artefacts has existed for well over two centuries. Roman brooches in particular have been in the forefront of this research both because of their ease of categorization and because they are found in large numbers on archaeological sites. Much work has been done on how they were made and on the technical choices available to the craftsmen. In particular, the choice of alloying agents (tin, lead, zinc) added to copper demonstrated a complex relationship between composition and typology, especially in the debate over Roman or local production. The technological restraints imposed on these artefacts by different alloy ratios have been studied in some detail, especially in terms of casting in liquid form, into a mould, or being wrought through beating with a hammer.

Wrap a Wreck! In Situ Conservation of a Ship on Land Suffering from Fungal Decay

Many sixteenth- to eighteenth-century shipwrecks have been found after land reclamation in parts of the former Zuiderzee, one of the busiest waterways in Dutch history. After the land fell dry, some shipwrecks were excavated, destroyed, reburied, or covered with sand or clay. In the late 1970s a method was developed to mitigate degradation processes of some of the wrecks remaining in good condition by wrapping them in plastic foil. The idea was that the plastic would prevent evaporation and lateral subsurface flow. Wet conditions prevent decomposing of wood by especially soft rot fungi. Oxygen will be rapidly depleted by decomposition of organic matter. Recent monitoring of wrapped shipwrecks has shown that this method of preventing rot worked exceptionally well. We adapted wrapping using new technology nowadays applied for sealing tunnels and landfills. We will present the implementation requirements, materials and new adapted method for wrapping shipwrecks.

Erosion and Errors: Testing the Use of Repeated LIDAR Analyses and Erosion Modelling for the Assessment and Prediction of Erosion of Archaeological Sites?

Slope soil erosion is one of the main threats to archaeological sites. Several methods were applied to establish the erosion rates at archaeological sites. Digital elevation models (DEMs) from three different dates were used. We compared the elevations from these three models to estimate erosion. We also applied the landscape evolution model LAPSUS with the available DEMs as basis. Spatial processing errors and effects of tillage and harvesting practices explain most of the DEM elevation differences between the recordings. Increased DEM resolution does not result in more precise or reliable erosion. The present technological level of landscape evolution modelling makes it possible to indicate areas most vulnerable to soil displacement by surface runoff erosion and tillage. Future research, using sediment and surface dating techniques such as deposit of radionuclides, heavy metals and OSL dating will provide a more accurate estimation of erosion rates and the subsequent impact on archaeological sites.

Between the Piles. Studying Excavation Photographs to Determine the Area of Physical Disturbance Caused by Piling in the Netherlands

Excavation photographs that show piles can be used to determine and measure the area of disturbance around piles. Until now, this has only been done at a small scale and with ideal examples. The present study shows that less ideal photographs can also be used to determine the disturbance around piles, at a much larger scale. Using predefined methods of documentation and registration, data can be collected about the disturbance of different types of piles, with varied piling techniques, in various burial environments and archaeological contexts. This data will be used in the second phase of the research to determine the loss of archaeological information due to piling.