Discovery Is Only The Beginning
How the application of multiple scientific analyses enhances our understanding of shipwrecks.
Shipwrecks and archaeology are an ideal combination not only to grab the public’s interest but also to stimulate further research
Shipwrecks and archaeology are an ideal combination not only to grab the public’s interest but also to stimulate further research by presenting closely dated material that does not normally survive on terrestrial sites . Historic England is currently involved in the investigation of numerous protected wreck sites, which allows us to employ a number of scientific techniques to identify, analyse and understand artefacts and ecofacts.
Artefacts recovered from the marine environment are classed as unstable and therefore undergo lengthy processes of desalination and conservation.
There is good evidence that prolonged storage in water furthers decay, and it is demanding on resources. One of the first tasks is to assess the materials that were recovered.
Using X-radiography to assess hidden artefacts
In the case of heavily concreted marine artefacts, techniques such as X-radiography are particularly useful. Not only do they allow for a quantification of multiple artefacts inside concretions, but also give an idea of the materials present and their state of preservation.
This information is used to devise and undertake a conservation treatment. In the case of organic materials, desalination is followed by impregnation with polyethylene glycol and vacuum freeze-drying. This technique eliminates the drying stresses caused by the high surface tension which water exerts on the weakened cell and fibre structures of wood or leather artefacts when simply air-drying without impregnation.
Conservators are often the first to spot unusual materials or anomalies.
Conservators spend a lot of time looking closely at artefacts and are often the first to spot unusual materials or anomalies.
They are perfectly placed to alert other specialists and often draw on their expertise to identify unknown materials.
Using material science to reveal new evidence
The Rooswijk was a Dutch East India Company vessel which sank on the treacherous Goodwin Sands, off Kent, in January 1740. The ship was outward bound for Batavia (modern-day Jakarta) with trade-goods. Now a protected wreck site, the ship's remains lie at a depth of some 20 metres. Since 2016 Dutch and British maritime archaeologists from Historic England and the Rijksdienst voor het Cultureel Erfgoed (Cultural Heritage Agency of the Netherlands) have worked together to carry out a joint investigation of the site.
Even the tiniest finds from the Rooswijk tell a story when analysed using modern scientific techniques.
X-rays of some of the concretions from the wreck showed bright spots scattered throughout. These areas were excavated by the conservators to reveal glass beads, only a few millimetres in size. Thousands more may have been lost to the shifting sands but fortunately some were trapped in the rust, like insects in amber.
The majority of the beads extracted so far are translucent and opaque yellow, a few are translucent green and opaque white, and a single larger, multi-coloured, chevron bead has been recovered.
Huge numbers of glass beads were produced in Europe and exported to Indonesia, the African continent and the Americas, where they were highly valued. From the fifteenth century, European beads increasingly competed with long-established bead makers in the Indo-Pacific.
Today the beads are valued by archaeologists, because they provide dateable evidence for long-distance maritime trade.
The design of popular beads remained virtually unchanged for years and many are plain, so chemical analysis is key to identifying different types. Furthermore, the precisely-dated Rooswijk beads may also help to answer archaeologists’ questions at sites around the world.
New insights using environmental science
Due to the waterlogged, anaerobic (oxygen-deprived) conditions at the seabed, organic remains from wrecks can be extremely well preserved. Samples of sediment from within the remains of a wreck site can produce macroscopic remains of plants, insects, bones, shells and microscopic pollen which provide information about food supplies, traded goods, living conditions, construction or packing materials.
From the Rooswijk, samples of sediment from within various objects have produced seed remains which appear to have been trapped within the objects during or soon after the wreck. A sample from a stoneware flagon, for example, produced numerous fragments of buckwheat (Fagopyrum esculentum Moench) seed coat or husks. The inedible seed coats were a by-product often used as a packing medium. The flagon, along with other breakable vessels, was probably packed in a crate with buckwheat husks as protection.
Also recovered from the Rooswijk were grains of wheat (Triticum aestivum/turgidum/durum type), flax (Linum usitatissimum), brassica species (Brassica/Sinapis sp.), bramble/raspberry (Rubus sp.), cannabis/hemp (Cannabis sativa) and, most surprisingly, five coconut (Cocos nucifera L.) shells. Seeds of wild grassland plants may derive from hay used for floor covering, bedding, or packing material.
While most of the edible plants were presumably on board as food supplies, the coconut shells remain a mystery.
Radiocarbon dating would be needed to confirm if the coconuts were contemporary with the ship or likely to be more recent.
Identifying the types of wood used on board ship – for fixtures and fittings, armaments and small arms, or domestic and personal effects – sheds light on past wood selection preferences and practices. When considered together with knowledge of the woods’ physical structures and characteristics, we can infer possible reasons as to why certain wood types were considered best-suited.
Analysis of around three hundred wooden remains recovered from the London (Hazell and Aitken 2019) has revealed that specific types of wood were used for particular purposes.
- Fraxinus (ash) was predominantly used to make the handspikes for manoeuvring cannon into firing position, as it is well suited to absorbing impact stresses – hence its traditional use for broom handles and snooker cues!
- Ulmus (elm) was used for pulley blocks and gun-carriage trucks as, unlike Quercus (oak), it is less prone to cracking; and Quercus heartwood was used to make casks as it is almost impermeable to moisture.
- Examining artefacts closely reveals additional details, such as the bark still present around two of the pulley-block pegs (one of which was probably Ilex-holly) and the decorative insert on the end of the tuning peg.
Dendrochronology tells the story of construction and repair
Dendrochronology or tree-ring dating is a powerful tool that can be used to aid the potential identification of a ship and enhance understanding of the wreck and associated wooden artefacts such as barrels and gun carriages. With appropriate targeted sampling strategies, it can provide dating evidence for the construction of and subsequent repairs to a ship, as well as ascertaining the geographical origin of those timbers, thus providing evidence relating to place of construction and longevity of the ship.
Its application to the recently listed inter-tidal wreck at Tankerton beach near Whitstable, Kent, revealed that the dated timbers represented at least two phases of felling and three different woodland sources.
A construction date towards the middle of the latter half of the sixteenth century was indicated, with major repairs being undertaken within at most two or three decades.
The oak framing timbers and hull planks proved to include timbers of both German and English origin.
The German timbers appearing to have been felled slightly earlier than the English. The ceiling planks, potentially either coeval with the oak timber repairs or slightly later, were conifer timbers of Scandinavian origin.
The multi-phase, multi-source group of timbers from the wreck at Tankerton highlights both the potential complexities of analysing wrecks and the fundamental information relating to date and provenance of timbers used in the construction and repair of a ship. The evidence from dendrochronology can be integrated into the wider archaeological investigation to complement the information derived from other methods of analysis.
Using science to recover evidence from maritime remains
The work undertaken on the three wreck sites helps us and others to understand these important heritage assets. Both the London and Rooswijk featured here are currently on the At Risk Register, which is an indication of their vulnerability.
The preservation conditions we encounter on wreck sites enable us to redress an imbalance currently prevalent in our archives: materials such as textile, leather or wood only survive in certain conditions, in this case, underwater.
Gaining knowledge and information
on raw products used, on trade routes or on the equipment and personal effects used by the crew allows us to paint a more complete and accurate picture of our past.
About the authors
Archaeological Conservator, Historic England
Angela holds a degree in archaeological conservation from the University of Applied Sciences, Berlin, and an MSc in Maritime Conservation Science from the University of Portsmouth. She joined Historic England as an Archaeological Conservator in 2007. Here she is responsible for advising on and undertaking research and investigative conservation on material retrieved from land and marine sites. She has a special interest in the conservation of waterlogged organic materials.
Materials Scientist, Historic England
Sarah Paynter studied Natural Sciences and worked in industry before obtaining a DPhil in Archaeological Science. She is now a materials scientist for Historic England and Honorary Research Fellow at the University of Sheffield. She uses analytical techniques to identify and investigate a wide range of heritage materials from buildings, collections and archaeological and maritime sites in the UK, from the Bronze Age to the twentieth century.
Archaeobotanist, Historic England
Ruth is an archaeobotanist with experience of northern European, Mediterranean and North African material. Her current role at Historic England is to provide specialist advice and sector support, to develop internal and collaborative partnership research projects, and to inform national and regional research frameworks. Her research interests include late Roman and early Islamic food and agriculture in North Africa, the past use of bracken, missing plant foods of Neolithic Britain, and aspects of British archaeobotany particularly from the Early to Middle Bronze Age and the early medieval migration period.
Zoë Hazell, BSc, MSc, PhD, MCIfA,
Senior Palaeoecologist at Historic England.
Zoë has a Geography background (Quaternary Science), with research experience in the reconstruction of past environments and landscapes. Her multidisciplinary interests mean that she has worked on diverse projects, from the use of peatlands to reconstruct past climatic conditions to the study of wood use through the identification of archaeological wood/charcoal remains.
Dendrochronologist, Historic England
Cathy has been a dendrochronologist since 1984. She oversees all tree-ring analyses commissioned by Historic England, provides advice to a wide range of external partners, and develops national standards. Her research interests include imported conifer timbers in post-medieval buildings, medieval farmhouses in south-west England, and past landscapes and woodland management.
Hazell, Z and Aitken, E 2019 The London protected wreck, The Nore, off Southend-on-Sea, Thames Estuary, Essex: Wood identifications and recording of wooden remains recovered between 2014 and 2016, Historic England Research Report 15/2019
Middleton, A 2016 Conservation of surface recovered artefacts from the Stirling Castle Protected Wreck, Historic England Research Report 45/2016
Middleton, A Pascoe, D and Paynter, S 2017 Conservation of surface recovered artefacts from the Invincible protected shipwreck site, Historic England Research Report 18/2017
Middleton, A Camidge, K Paynter, S and Gleba, M 2018 Investigation and conservation of surface recovered artefacts from HMS Colossus, Historic England Research Report 26/2018