Filling the Gaps in Heritage Science research #2 Decay mechanisms and rates of decay of the built historic environment

Continuing our series of posts to map research to the gaps in knowledge and practice identified in the National Heritage Science Strategy (NHSS), this second request for input covers research into decay mechanisms and rates of decay of the built historic environment.

The NHSS identified seven specific topics that would benefit from greater understanding.

These are:

  • the behaviour and methods of control of soluble salts in buildings
  • the impact of multi-pollutant urban environments and nitrogen oxides in particular on building fabric
  • the impact of the use of inappropriate materials for repair
  • the impact of non-conservation stone cleaning which can lead to acid decay and increased microbial growth
  • the interaction between moisture, microbes (e.g. biofilms) and salts in stone degradation
  • vibration damage to historic monuments
  • the impact of fire resistant treatments on the longevity of organic materials (i.e. thatch)

Our survey monkey form at https://www.surveymonkey.co.uk/r/DXKHX2V can be used to record information about research in any of these areas, published or unpublished, since 2009.

Please circulate this link/posting and help us to build up, and share, knowledge of existing research as well as identify which gaps remain so that we can promote remaining opportunities to researchers, funders and policy makers.

Many thanks
National Heritage Science Forum

Filling the Gaps in Heritage Science research #1 Understanding decay mechanisms and rates of decay of movable items

In 2015 NHSF commissioned an initial review of the heritage science research that had been carried out since 2009. The resulting report ‘Filling the Gaps’ maps research listed on the Gateway to Research (i.e. funded by the UK Research Councils) to the gaps in knowledge and practice identified in “The role of science in the management of the UK’s heritage”, one of the three evidence reports produced to support the development of the National Heritage Science Strategy.

NHSF now wants to work with the heritage science community to ‘crowd-source’ knowledge of heritage science research to further ‘fill the gaps’ in the 10 topics identified in the evidence report.

We want to identify the gaps in knowledge and practice that remain so that we can promote them to researchers and funders as opportunities to be addressed in the future. We also want to be able to share information on where to find research that has been carried out.

We’re going to blog every couple of days with a new topic from the strategy, providing a link to the survey form you can use to add your knowledge of research, published or unpublished since 2009.

We start with eleven themes from the topic ‘Understanding decay mechanisms and rates of decay of movable items’

The National Heritage Science Strategy evidence report identified a need for improved understanding of:

·      acceptable limits of RH & temperature in degradation of organic materials and metals

·      the impact of cumulative light exposure on different materials

·      the effectiveness of low oxygen/anoxic conditions for storage and display

·      tolerable levels of particulate and gaseous pollutants

·      the effects of high pressure water mist for fire control on organic materials

·      vibration impacts from increased visitor numbers and during transport

·      the degradation mechanisms of metal polyphenol dyes (black dyes, i.e. iron gall ink)

·      the degradation mechanisms of leather

·      the deterioration of biological molecular structure of natural history collections

·      methods to control soluble/insoluble salts in collections (ceramics, glass and stone)

·      how often cleaning of dust should take place

Please add your knowledge of research that addresses any of these areas against the relevant headings in the survey at https://www.surveymonkey.co.uk/r/DWSDVPD.

It can be published or unpublished research, completed or underway. Our only criteria is that the project started in or after 2009. You can complete the survey multiple times to add more than one piece of information against the same research area.

The eleven areas are listed as separate survey questions with fields for  Author(s), Lead organisation, Project title etc. You don’t have to fill in all the information but clearly the more you can provide, the more helpful a resource we’ll be able to develop.

We have also asked for information on the funding source and approximate amount of funding for the research/projects. This information is optional but if you can add it, it will help us to build up a picture of how heritage science research has been funded in recent years, which will be particularly useful as we potentially move to a new funding environment following the outcome of the UK Referendum vote to leave the European Union.

Many thanks for your contribution to this project – please share this link amongst your colleagues!
National Heritage Science Forum

 

 

Five minutes with…Fay Worley, Zooarchaeologist at Historic England

Our second blog post during the Festival of Archaeology comes from Fay Worley, Zooarchaeologist at Historic England. In this ‘five minutes with…’ posts she describes to us how she became interested in zooarchaeology and shares examples of her work in the field at Historic England.

I’ve been interested in animals, skeletons, historic places and field archaeology since I was a child. By the time I reached university I’d realised that I could combine these interests in zooarchaeology. I undertook a Bioarchaeology BSc and zooarchaeology focussed PhD at the University of Bradford, including a placement year spent in developer-funded and curatorial archaeology. I then worked as an animal bone specialist at Oxford Archaeology before moving to English Heritage, the predecessor to Historic England.

As a zooarchaeologist, I analyse and report on animal bone assemblages excavated from archaeological sites. For me, this involves examining the bone fragments, identifying them to animal species and skeleton part based on their shape, and looking for evidence of their life history, and what has happened to them since their death. These data are used to form interpretations about the animals, people and past activities at the archaeological site, and in combination with other assemblages, to inform broader studies of cultural behaviours.

Working as a zooarchaeologist at Historic England I also have an advisory role. This includes working with the Professional Zooarchaeology Group and Association for Environmental Archaeology, providing training, and helping to manage a large reference collection. It also allows me to be involved in external projects and research partnerships – I’m currently part of the University of Reading and Historic England team excavating at Marden and Wilsford henges in Wiltshire.

I love that my role is really varied and often provides challenges or exciting discoveries. The most challenging project recently, and one that I feel most proud of, was the production of guidelines for zooarchaeology with my colleague Poly Baker. It was an epic task, with contributions from many other zooarchaeologists, and the end result has been well received.

In terms of exciting discoveries, two completely different assemblages come to mind. The first is from the earliest fills of Wilsford henge ditch, excavated last year, and currently sitting on my lab benches. The assemblage is almost exclusively large cattle bones from at least four or five bulls and cows, which were butchered using flint tools around four and a half thousand years ago. Cuts of meat were removed and some bones were scorched and smashed open, before the remains were dumped in the ditch at the entrance to the henge. Along with the bones was a rather lovely red deer antler pick, which may have been used to dig the ditch.

Fig1_LateNeolithicCattleBones
Figure 1. Examining some of the Late Neolithic cattle bones from Wilsford henge, Wilts

The second is a Roman dog, which died as a young adult and was carefully buried in a stone and tile cist at the site of a villa in Northamptonshire. When I started examining the dog I realised that it is very small, comparable in height to the modern Chihuahua or Maltese breeds. Researching other archaeological dogs has shown that it is one of the smallest adult dogs ever found in Roman Britain. Its skeleton is also providing clues to its appearance and life style which I’m hoping to be able to investigate further with the University of Nottingham.

Fig2_RomanLapDogNorthamptonshire
Figure 2. A small Roman lap dog from Northamptonshire

 

 

Heritage Science in Action…archaeobotany

As the 2016 Festival of Archaeology enters its final few days, we have a couple of blogs from heritage scientists at Historic England. The first, from Dr Ruth Pelling, describes her work as an archaeobotanist to identify and interpret plant remains from Historic England excavation projects or funded projects. She talks about working with examples of charred grain from the Pitt-Rivers Archive and how this can increase our knowledge of early farming.

Heritage Science in Action …archaeobotany

Dr Ruth Pelling, Senior Archaeobotanist, Historic England

Archaeobotany is the study of plant remains from archaeological sites. Most commonly this involves the examination of charred grain, chaff, pulses, fruit and nut remains, tubers, rhizomes, weed seeds, and charcoal which have survived as a result of being burnt. Plants can also be preserved in anaerobic deposits where oxygen is excluded (most commonly due to water-logging) thus preventing bacterial and fungal action. Leaves and even flowers may survive in such conditions. A third type of preservation is mineral replacement, in which all or part of the structure of the plant is replaced by mineral salts, most commonly calcium phosphate, or mineral preserved remains where material is preserved due to its proximity to metal corrosion products. Identification is based on the physical characteristics of the item: the morphology (shape and form), surface cell structure, and internal cell structure.

My job as the senior archaeobotanist is to identify and interpret plant remains from Historic England excavation projects or funded projects. I also provide advice and support to other archaeobotanists, including those employed in the commercial sector. I identify research priorities in archaeobotany, either locally or nationally, and answer individual enquiries from helping with identification to developing sampling strategies. At the moment I am working on a really exciting project examining material held in the Pitt-Rivers archive at Salisbury Museum.

Augustus Henry Lane-Fox Pitt Rivers (14 April 1827 – 4 May 1900) was one of the leading anthropologists and archaeologists of the Victorian age. He conducted a number of excavations, particularly in the area of Cranborne Chase in Dorset, and was an avid collector of antiquities and ethnographic artefacts. In 1975 Salisbury and South Wiltshire Museum was gifted the Wessex collections by HM Treasury. Amongst the archive were a number of cigar and pill boxes full of charred grain, complete with the original labels and identifications. It is a great honour to be able to look at this material and re-identify the cereal remains with a more scientific eye.

Ruth at microscope
Ruth Pelling at the Microscope

Pitt-Rivers did not employ modern sampling and flotation methods as practiced today, so his plant samples are derived from grain caches which were substantial enough to be spotted during excavation. As such the material represents unusual burning events of stored grainor grain accidentally burnt during processing events, as opposed to the everyday processing losses we usually encounter. A complete catalogue of the samples, possibly coupled with radiocarbon dating, will enhance our knowledge of Iron Age and Roman farming in the Dorset region and highlights the value of archived material, particularly when contextual information is as thorough as that provided by Pitt-Rivers.

Amongst the samples in the collection are two boxes of grain from the Swiss Lake settlements labelled ‘burnt wheat from the Swiss Lakes, Brice Wright’s Sale’. The Swiss Neolithic lake dwellings were first discovered in the mid-19th century when wooden house posts were exposed in Lake Zurich during the winter of 1853-4 due to exceptionally low water levels. Finds from the sites were sold to visitors from all over the world in the late 19th century. This included samples of plant remains. It is likely that the Pitt-Rivers samples derive from Robenhausen, where archaeological layers dated from the Neolithic (4th and 3rd millennium BC) to the Late Bronze Age. Interpretation is limited as there is little by way of contextual information but the material shows how amazing preservation of this ancient plant material can be. Burning grain deposits were presumably fairly rapidly extinguished when the house platforms fell into the water, where they lay in stable waterlogged conditions within the lake silts until discovered thousands of years later. Similarly remarkable preservation has been uncovered at the site of Must Farm in Cambridgeshire which is currently being studied in Cambridge.

PR-SwissGrain1d 5-8mmscale-1
Wheat grain from the Swiss Lakes, Pitt-Rivers Archive
PR-SwissRachisGlume1a 6-25mmscale-2
Wheat rachis with attached glumes from Swiss Lakes, Pitt-Rivers Archive

 

Further information:

www.salisburymuseum.org.uk/collections/pitt-rivers

www.mustfarm.com/

https://historicengland.org.uk/research/approaches/research-methods/Archaeology/archaeobotany/

 

Collection Surveys as Part of Library Document Supply Chain

In our final May posting from the SEAHA cohort, Natalie Brown describes her research to develop a simple, non-destructive method for assessing the ‘health’ of paper-based collections that can be carried out as part of daily operations.

Natalie will be chairing one of the sessions at the 2nd International SEAHA conference which is being held in Oxford, UK 20th-21st June. The conference explores heritage science from many angles, including sessions on policy and management, imaging, environments, analytics, novel techniques and conservation techniques. For further information, including the full programme and how to book see: www.seaha-cdt.ac.uk/seaha-conference-2016/

Collection Surveys as Part of Library Document Supply Chain

By Natalie Brown, UCL Institute for Sustainable Heritage

Acknowledgements:

Matija Strlic, UCL Institute for Sustainable Heritage

Tom Fearn, UCL Department of Statistical Science

Dirk Lichtblau, Lichtblau e.K. www.lichtblau-germany.com/

David Howell, Bodleian Library www.bodleian.ox.ac.uk/bodley

Fenella France, Library of Congress http://www.loc.gov/preservation/scientists/ 

Memory institutions, such as libraries and archives offer a unique, multi-faceted service to the public. They are centres of lifelong learning that foster tangible links to the past by enabling access to information. Within these institutions preservation measures are set out to ensure the prolonged life of paper collections, often focusing on the ‘health’, or the overall condition of the collection relating to its usability. To understand the overall condition of a paper object, several chemical and physical parameters are considered including acidity, lignin content, additives in the paper, the sizing and tensile strength. Through my research I aim to create a straightforward and non-destructive method for library staff to assess and understand the ‘health’ and deterioration of their collections, integrated into the daily library operation.

Within institutions, gathering data on their collection’s ‘health’ is an important preservation measure; however, it requires surveys that can often be resource-intensive and rely on the sensory judgment of experts or even semi-destructive tests. As non-destructive testing advances, spectroscopy has become an attractive alternative, where the chemical and physical parameters important for preservation can be analysed quickly and without causing physical change to the object. My project specifically uses near infrared-spectroscopy (NIR), a method that uses the near-infrared region of the electromagnetic spectrum, with the assistance of multivariate chemometrics to help interpret the complex spectra of the object (Fig. 1).

NIR spectra of European rag and Chinese Xuan papers

Figure 1. The NIR spectrum of a European rag paper (pink) and NIR spectrum Chinese Xuan paper (blue). Although the papers are very different, their spectra look almost identical.

Past research in this area has predominantly focused on the characterization of Western papers. A user friendly instrument, SurveNIR (www.science4heritage.org/survenir/), has been developed by the project’s industrial partner Lichtblau e.K. (Dresden, Germany). SurveNIR is able to characterize 15 paper properties important for preservation. The first stage of this project has been to build on the previous research and extend the application of NIR technology, developing models to analyze different Asian papers. Laboratory tests were performed on a reference collection of 200 19th and 20th Century Chinese papers and several NIR applications were successfully developed for these papers including pH, degree of polymerization, tensile strength, lignin content, and dating. Working closely with Lichtblau e.K. it is the hope that in the future I will be able to develop NIR applications for other Asian papers.

Figure 2. Two samples of 19th Century Chinese handmade paper that were used to create NIR models.

In the second phase of the project I will be working closely with two heritage partners; the Bodleian Libraries, the University of Oxford and the Library of Congress, (Washington D.C.). During this time, NIR tools will be used to conduct mass condition surveys on real library collections. By working within these institutions I can investigate the needs of practitioners and identify specific technology deployment challenges to develop a methodology that implements these tools. As the technology is highly accessible there is scope for several stakeholders to engage with the project, including book fetchers, conservators, curators, and institutional visitors.

SurveNIR

Figure 3. Natalie using SurveNIR to analyse European paper samples  © D. Lichtblau

The final stage of this project will be data analysis. A huge amount of data will be collected while working at the case study libraries, and thousands of books of characterised. The information gathered could feed into future risk assessment, trend predictions, and prevention of accelerated deterioration due to the environment. From this, the life expectancy of collections can be assessed more easily, stricter preventative measures can be implemented where needed and environmental parameters can be loosened.

 

 

Mitigating dampness in historic buildings: when ancient techniques and science come together

In the second of our posts from SEAHA students, as they prepare for the 2nd International SEAHA conference on 20-21 June, we hear from Lucie Fusade, SEAHA Doctoral Student at the University of Oxford, School of Geography and the Environment on how ancient techniques and science can come together to mitigate dampness in historic buildings.

Mitigating Dampness in Historic Buildings: When Ancient Techniques and Science Comes Together

By Lucie Fusade, University of Oxford, School of Geography and the Environment

This research looks at the use of traditional materials such as lime mortar and additives in order to mitigate driving-rain ingress to historic buildings. It aims to develop a repair mortar for specific conservation issues while gaining a scientific understanding of the behaviour of the materials. This is why this research has been co-created with the University of Oxford, Historic England Building Conservation and Research Team and the Churches Conservation Trust (CCT), as part of the EPSRC SEAHA centre for doctoral training. This collaboration allows the research to undertake a combination of laboratory experiments and field trials in order to fully assess the properties of the mortars tested.

North HuishP1000119
St. Mary’s Church, North Huish, a church under the care of the CCT

Lime mortar is a traditional building material, which technology has been extensively developed by the Romans. A mortar can be made with many combinations of binder, aggregates, water and additives. In most of England’s historic buildings the binder traditionally used is lime, sand usually used as the aggregate. Lime, a breathable and soft material, is the material produced for the burning of limestone. Most of the repairs to historic masonry require the use of mortar. Although cement, an impermeable material, was used extensively since the late 19th century, lime-based mortar is now mainly used.

In England, many historic buildings of architectural, national or local significance, are particularly exposed to harmful environments, especially wind and driving rain. Rain water and moisture are one of the key factors in the deterioration of building materials, leading for instance to biological growth and dampness. To ensure preservation of historic masonry, rain penetration needs to be mitigated and moisture drawn out of the wall. These are the main roles of masonry joints and especially of the surface mortar, called pointing mortar. The joints indeed contribute to take harmful soluble salts away from the historic stones. Practitioners said that, when done correctly, repointing intervention is the most significant repair to assist waterproofing of a wall. Dampness can easily occur in masonry that has been repaired with cement rather than lime and more damage to the masonry units done.

repointing
Repointing intervention

Developing a suitable mortar, using traditional material, for repointing intervention is therefore necessary in order to preserve the historic masonry. The main requirements for a lime-based mortar to be used in pointing intervention on buildings exposed to dampness are that the mortar should be softer than the surrounding masonry, porous, highly permeable, quick at drying and especially able to cure under damp conditions.

Considering these criteria, it is necessary to enhance the properties of the lime mortars commonly used. They have a tendency to be too strong for the surrounding masonry after several years and sometimes not able to dry out quickly enough. Thus, additives, such as wood ash or crushed stones, can be added to the composition to enhance its different mechanical or physical properties. The repair mortar is then designed to meet specific conservation issues.

mortars samples
Samples of lime mortars made with natural-hydraulic lime and different concentrations of wood ash

 

The first phase of this research focuses on the use of wood ash as additives. Wood ash has been used in the past, by Romans for instance, to moderate water ingress. However, a scientific understanding of its effect is lacking. Previous research done during an MRes has demonstrated that wood ash added to lime mortar has a clear impact on the performance of the material in increasing the hardening process of the mortar, called carbonation, as well as the permeability and the porosity. The positive impact of wood ash on the permeability of lime mortar seems to be due to the high number of fine particles it contains, enhancing the micro-porosity.

The research aims to characterise the physical and chemical roles played by wood ash in lime-based mortars. Working with an experienced mason, a series of mortar samples was made with different concentrations of wood ash, 0, 10, 20, 30, 40, 70 and 100 percent, as part of the aggregate, and mixed with natural-hydraulic (NHL 3.5) and non hydraulic lime (lime putty). Prior to on-site investigation, the research involves laboratory experiments at the Oxford Rock Breakdown Laboratory (OxRBL). Properties such as the water absorption coefficient, the open porosity, the vapour permeability, the degree of carbonation and the flexural and compressive strength are assessed using gravimetric tests, thin sections microscopy and scanning electron microscopy.

Based on the results obtained in laboratory, some mixes will be applied on test walls outside at Wytham Woods in order to evaluate their performance when exposed to driving-rain. Later on, selected mixes will be applied to damp historic buildings cared for by the CCT and in collaboration with expert practitioners from Historic England. Combining ancient materials and workmanship with scientific investigation contributes to sustainable and targeted conservation interventions.

lab experiment
Experimental setting to determine the open porosity of lime mortars

 

Spotlight on SEAHA…Spotlight on Plastics

May’s blog posts are a ‘spotlight on SEAHA’ in preparation for the upcoming 2nd International SEAHA Conference in June. The posts will highlight SEAHA student research with the first post ‘Spotlight on Plastics’ from Anna Pokorska, Postgraduate Research Student, Institute for Sustainable Heritage, UCL.

Spotlight on Plastics

By Anna Pokorska, Postgraduate Research Student, Institute for Sustainable Heritage, UCL

Plastic materials have quickly become ubiquitous in our everyday lives, from ordinary use objects to high value works of art and design. They also have a contradictory reputation – on one hand plastics are thought of as durable due to the fact that they do not biodegrade. However, they are also often used as temporary and cheap substitutes for more valuable materials and not expected to last as long. In fact, the early plastics have intrinsic flaws which contribute to their degradation due to the largely experimental character of their production. Nevertheless, plastic objects of both natures can now be found in heritage collections. Artists and designers have also happily experimented with the use of the materials creating innovative artworks but also, at the same time, considerable challenges to conservators. Another critical issue is the sheer amount of different plastics and their combinations with various additives now available. However, in recent decades there has been a lot of research carried out in the field of conservation of these materials. Contributing to that movement is a project based at the Institute for Sustainable Heritage (ISH) at UCL which will investigate the stability of plastics to visible light as encountered in a museum or gallery environment.

V&A 20th century gallery display of plastics
Part of the V&A’s 20th century gallery displaying a variety of plastic artefacts

 

It is common knowledge that UV radiation is harmful to most materials and is therefore filtered out in heritage institutions. However, the sensitivity of various types of plastic formulations to visible light is not that well understood and consequently museum lighting guidelines for them remain somewhat vague and under-researched. Through collaboration with the Victoria and Albert Museum and Philips, the most up-to-date knowledge of plastic degradation and preservation will be brought together with cutting-edge lighting technology research. The main goal of this project will be to identify the long-term effect of visible light on the physical appearance and chemical structure of modern materials. Aspects of deterioration such as discolouration and crazing will be related to changes in the molecular structure of the materials thus increasing our understanding of the processes and visual impact of light-induced degradation.

Infrared spectroscopic analysis of degraded plastic sample
Carrying out infrared spectroscopic analysis of a degraded plastic sample at the Institute for Sustainable Heritage

 

A wide range of plastic types which will be tested will help identify those that may be sensitive to visible light exposure and dispel some of the contrasting results found in research so far. Following from that the project will focus more closely on the individual contribution of different parts of the visible light spectrum towards plastic decay. This will not only further expand our knowledge of light degradation but may also present an opportunity to reduce some of that damaging potential and preserve plastic artefacts for longer. The results from this project will also contribute towards improving lighting guidelines for display of plastic objects in collections by providing more specific recommendations for particular formulations as well as help define a more robust methodology for future studies.

SEAHA,  the EPSRC Centre for Doctoral Training in Science and Engineering in Arts Heritage and Archaeology, is a unique initiative that brings together academic, heritage and industry partners over an 8 year period (2014-2022) to meet challenges set by the heritage sector, industry and government.

SEAHA will hold its second international conference in Oxford on 20th-21st June. Alongside keynote speakers Sir Philip Campbell (Editor-in-Chief, Nature), Dr Ewan Hyslop (Head of Technical Research and Science, Historic Environment Scotland) and Dr Philippe Walter (Head of Laboratory of Molecular and Structural Archaeology, Sorbonne Universites, CNRS, UPMC), many of the SEAHA students will be presenting their work.

To find out more about the conference, visit www.seaha-cdt.ac.uk/seaha-conference-2016/