Improving the evaluation of conservation treatments for deteriorating sandstone in built heritage (Spotlight on SEAHA)

Our third ‘Spotlight on SEAHA’ guest post comes from Richard Grove who outlines his research into finding out whether sandstone treatments are providing the protection that was intended.


This research sets out to create practical guidance for assessing the effectiveness of historic stonework treatments. Many sandstone structures, artefacts, and archaeological sites have been treated with some sort of consolidating coating where the surface or structure has been eroded by time, weather or the action of humans or animals. As yet, there is no standard procedure for assessment, meaning there is no way of telling if the treatments currently used are helping or damaging the thing they are meant to protect.

The guidance resulting from this project can be adopted by both academic and commercial conservators, as it will be applicable to a wide range of treatments across the world, and not just a single type. It will change the way all who work on sandstone heritage understand how the treatments they use interact with the stone, by using heritage science to answer complex questions on historic materials.

Image of Oxford's Rock Breakdown Laboratory
Part of Oxford’s Rock Breakdown Laboratory where samples will be treated (image (c) Richard Grove)

The project will combine a range of laboratory based tests combined with simulated and real world case studies. There will be samples taken of sandstone types commonly used in conservation works, and found on historic buildings around the world. Samples will be weathered in our laboratory, to emulate the advanced decay of some of the most iconic sites globally. These samples will then be treated with a range of commercially available solutions; after which they will be subjected to some further accelerated weathering.

Image of stone samples undergoing internal testing
Stone samples undergoing internal testing (image (c) Richard Grove)

The samples will be subject to a range of tests throughout this process, from their ability to absorb and let out moisture (see image of the Karsten Tube Experiment below), to their strength under a range of forces such as compression and twisting. These tests will provide us with a range of measurements from which we can assess the performance of all available treatments in a range of situations, and help us design a model for testing on site without the need to take samples from the vulnerable sites themselves.

Image of stone sample undergoing Karsten Tube testing
Karsten Tube Testing, measuring the moisture uptake of the stone samples (image (c) Richard Grove)

This research is intended to benefit anyone who has an involvement in the maintenance and repair of sandstone in a range of settings, from archaeological sites such as Palaeolithic cave sites in the Near East, to modern municipal buildings in the UK. The range of situations where sandstone is employed is vast, and everyone involved in its maintenance or care will be able to benefit from the findings of this research.

Watch this space! Keep an eye on the SEAHA website and oxrbl.com for information on the project as it develops.


The 3rd International Conference on Science and Engineering in Arts, Heritage and Archaeology (SEAHA) will take place on 19-20 June 2017 at the University of Brighton. Click here to view the programme of themed sessions and flash presentations, and here to register.

Learning from nature: evaluating site-based conservation approaches to mitigating climatic risks to earthen heritage sites in north west China (Spotlight on SEAHA)

Next up in our Spotllight on SEAHA series is a guest post from Jenny Richards, presenting her research into the conservation of sites made from one of the oldest known materials: earth. 


Earth is one of the oldest and most universal construction materials. It has been used by humans since Neolithic times to build structures such as homes, temples and even entire cities.

As built earthen sites are found on every continent, they provide us with the opportunity to improve our understanding of past cultures across the world and learn how traditional buildings were used; the sites are also accessible for many people to visit and enjoy.

However, earthen structures are susceptible to damage by climatic and other natural processes such as earthquakes. Despite this vulnerability, the conservation of earthen sites has lagged behind other building materials, partly because earth has been viewed as a primitive building material. This has meant that many conservation methods have either i) been ineffective, ii) only worked for a few years, or iii) in extreme cases, have sped up the rate of degradation.

My research is aiming to use heritage science to improve the long-term conservation of earthen heritage by understanding how climatic and environmental processes interact with earthen sites. In my research, I will also investigate the potential of using natural, site-scale conservation methods such as planting a windbreak downwind of the site to reduce the impact of the climate on the earthen site.

photo_1_Richards[736]
The ancient city of Souyang located on the Silk Road, China. Each of the outer city walls are about 500 m in length. Source: Dunhuang Academy
My research is based at the ancient city of Souyang, located on the Silk Road in north west China. Souyang is one of the most intact cities from the Han, Sui and Tang Dynasties and is an exceptional example of a frontier defence city. However, its walls are degrading and future climatic changes are expected to increase rates of degradation.

photo_2_Richards[735]
Examples of deterioration seen at Souyang, caused by a) cracking, b) vegetation growth, and c) wind. Source: Dunhuang Academy
I am undertaking my research in collaboration with the Dunhuang Academy. This has meant that I have been able to utilise the extensive climate and vegetation data they have already collected. I will also be undertaking my own fieldwork at the site to investigate the relationship between microclimatic conditions and the extent to which the walls are degraded.

In addition to fieldwork at Souyang, I am using a computer model to understand how earthen heritage is affected by climatic processes and vegetation patterns. The computer model allows me to model complex interacting processes, use different initial conditions to understand how different climatic scenarios would affect the earthen site, and model the long-term impact of potential conservation strategies.

The Dunhuang Academy will be able to implement any findings at Souyang to improve its conservation strategy. The model will hopefully be able to be applied to other earthen heritage sites.

Find out more
Read more at: http://www.seaha-cdt.ac.uk/people/meet-our-students/
Follow updates on Twitter: @jcjrichards18


The 3rd International Conference on Science and Engineering in Arts, Heritage and Archaeology (SEAHA) will take place on 19-20 June 2017 at the University of Brighton. Click here to view the programme of themed sessions and flash presentations, and here to register.

Ink-credible: Developing sensors utilising ink jet printing for the Mary Rose Museum (Spotlight on SEAHA)

This month, we will be publishing a series of posts from SEAHA (Science and Engineering in Arts, Heritage and Archaeology) students on their research, in the run-up to the 3rd International SEAHA Conference in June. First up, Sarah Hunt talks about her project developing acid sensors for the Mary Rose Museum – using ink jet printing.


The aim of my project is to develop a real time acetic acid sensor to be trialled in display cases at the Mary Rose Museum, Portsmouth. I will utilise piezoelectric quartz crystal (PQCs) technology, which has the benefit of being small and affordable.

PQCs are electronic components that act as micro-balances: the quartz crystal is sensitive to very small changes in mass that occur on its surface and will result in a measurable signal, observed as a frequency change. Hence if a coating that interacts with a pollutant of interest, for example acetic acid, is applied to the surface of a PQC, a measurable response will be observed. The resulting system could be used to affordably monitor that pollutant.

The method used to apply the thin coating onto the PQC needs to create a uniform layer, with good control over the mass of coating deposited. I am currently trialling ink jet printing as a method to deposit the thin film, as this method can offer very fine control over the location and amount of deposited material (fig. 1 and 2).

fig 1a
Fig. 1: The research printer used to coat PQCs in a thin film. It consists of a metal stage, which the PQC is attached to during printing; four print heads, which are connected to different four fluid reservoirs; a vertical camera to help pinpoint the required printing locations; and a horizontal camera with a strobing LED opposite to image the drops during jetting.
fig 1b
Fig. 2: An image captured from the horizontal camera during jetting of a lead oxide solution.

Inkjet printing can be performed with a wide range of materials in solution or suspension, including metal nanoparticles, hence this technique could be used for a wide range of coatings. It can also be used to create thin films of different shapes, such as circular patterns, and hence apply a film over the entirety of the PQC surface (fig. 3 & 4).

fig 2
Fig. 3: This shows two PQCs, the one on the left is uncoated. The PQC on the right was imaged after printing a polymer resin in a square array onto its surface.
fig 3
Fig. 4: A circular printed array

This project is still in its early stages – however, if a real time acetic acid sensor can be developed, with good accuracy and low detection limits, it will be highly beneficial for any museum concerned about acetic acids during storage and display of artefacts. The Mary Rose Museum, which houses a large collection of polyethylene glycol (PEG) treated waterlogged wood, will gain a better understanding of organic acid emissions from PEG treated wood and the implications of this on the collection.

Moreover, if this project is successful, I am hopeful that further Heritage Science research will be performed utilising PQCs, taking advantage of their adaptability by changing the coating applied. Early warning dosimeters for specific heritage materials could be developed, or even personalised air quality sensors that are sensitive to pollutants chosen by the museum. Perhaps this is a long way off, but quite an exciting proposal.

Alongside Heritage Science, environmental sensors are widely used in society, particularly with the increasing awareness of indoor air quality and health. Advances in PQC sensors from Heritage Science could be beneficial for this industry.

Want to find out more?
I will have a poster at the SEAHA 2017, Brighton – come and chat to me about it.
Email: sarah.hunt.15@ucl.ac.uk
Twitter: @Sarah_JayneHunt


The 3rd International Conference on Science and Engineering in Arts, Heritage and Archaeology (SEAHA) will take place on 19-20 June 2017 at the University of Brighton. Click here to view the programme of themed sessions and flash presentations, and here to register.

Spotlight on SEAHA

Throughout this month, in anticipation of the SEAHA Conference 2017 in June, we’ll be shining a ‘Spotlight on SEAHA‘ through a series of guest posts in which SEAHA students will be presenting their research. Features will look at conservation on the Silk Road, innovative uses of ink-jet printing, and much more.

Interested? The 3rd International Conference on Science and Engineering in Arts, Heritage, and Archaeology (SEAHA) will be held at the University of Brighton on 19-20 June 2017. For more information, including the programme and how to register, visit the SEAHA website.

The NHSF is also offering bursaries for Early Career Researchers, to cover the £120 two-day registration fee. The deadline for applications is the 12 May 2017 see here for more details.

Ground Penetrating Radar (GPR) Survey at Kedleston Hall, Derby

Our final #BSW17 post come from Erica Carrick (EMC Radar Consulting) and Rachael Hall (National Trust). Erica describes how Ground Penetrating Radar is being used to assess the internal structure of the Marble Hall at Kedleston Hall, Derby.

For some time, the National Trust has been concerned about possible distortion in the floor of the beautiful Marble Hall at Kedleston. Walking across the floor gives the impression that the floor may be deflecting in certain areas. EMC Radar Consulting was commissioned by the National Trust to carry out a GPR survey of the floor to examine its structure and confirm the findings of a laser survey carried out previously.

GPR works by transmitting radio waves into the ground. Every time that these electromagnetic pulses meet a change of materials, part of the signal is returned to the receiver antenna. As the radar crosses the floor, a vertical pattern of the boundaries between the different materials below the surface is built up. The radar cannot identify the materials but it does distinguish where one type of material ends and another begins so we are able to look at the internal structure of the floor.

Scanning marble hall floor at Kedleston
Scanning the marble hall floor at Kedleston Hall.

This is essentially the same technology as is used in other types of radar but the wavelength of the radio waves is much shorter than, for example, aerial radar. Since the floor itself is a relatively thin structure, it is essential to use a high frequency radar, in this case a 4GHz system. High frequency radars have very short wavelengths. This means that they cannot be used for deep investigations since the number of wavelengths transmitted is limited (independently of the frequency). However, since radars measure in terms of their wavelength, they have the advantage of being able to detect and measure on a much finer basis than a typical radar that might be used on an archaeological site in open ground.

Kedleston live scan data
Kedleston Hall live scan data
Comparative data from scan of Kedleston Marble Hall
Comparative data from scan of Kedleston Hall Marble Hall

The two radar traces shown are vertical images from the West side of the Marble Hall (below) and from the centre of the Hall (above). Both traces show the layers of marble, supported by brick with a sand/lime mix below and the evidence of wooden floorboards beneath that. There is a big difference between the two results. The lower trace shows even banding across the whole floor, suggesting that there is relatively little deflection along this line. The upper trace, however, shows that the sand/lime layer increases and then decreases across the line of the floor, suggesting that at least part of this section has moved.

The data from the survey is being combined into a 3-dimensional set from which we will also be able to extract horizontal views across the entire floor.

Scanning the Marble Hall floor at Kedleston
Scanning the Marble Hall floor at Kedleston Hall

Find out more about Kedleston Hall, National Trust

Caring for paintings with the use of a simple camera

As we near the end of our series of posts for British Science Week Vladimir Vilde, a PhD student at UCL, working with English Heritage and David Thickett, Senior Conservation Scientist at English Heritage describe an innovative, low-cost approach to monitoring the condition of paintings across English Heritage properties.

One of the many roles of English Heritage is the management of more than one thousand paintings housed across numerous historic properties. To ensure their care and suitability for display they require regular examination by paintings conservators and conservation scientists. However, given the large number of works of art in the collection, and their geography, this can be very difficult to perform in great detail. Scientific analysis across the entire collection is not possible in this context as it represents a logistical and financial challenge. Instruments can be expensive, hard to move, or simply not tailored for non-invasive analysis.

Painting collection at Apsley House (C) English Heritage
Painting collection at Apsley House. This picture shows the challenging but magnificent work environment.

English Heritage has teamed up with researchers at UCL’s Material Studies Laboratory and the imaging and sensing company LAVision to investigate the potential of exploiting the technology of consumer products, such as laptops and digital cameras, to monitor change in canvas paintings. Such technologies are readily available to conservators and already in use during routine investigations. Cameras in particular are often used in their simplest function, to capture an image, but various techniques of image processing can be used to enhance the observations resulting from just a few photographs.

Digital image correlation (DIC) is one of these techniques and under investigation through this collaborative research. Using two successive pictures, DIC can measure the displacement on an object, which can be used to highlight defects or cracks in a painted surface. There are a large range of specialist cameras that are available on the market for DIC, but the technology is essentially is based on comparisons between two or more photographs, and therefore any camera can be used. This enables the possibility of measuring on site quite easily with off the shelf, accessible tools, but also offers the opportunity to deploy a larger monitoring system across English Heritage properties, due to the low cost of such a setup. The output results are images overlaid with colours according to the amount of displacement captured between successive photographs, which makes it easy to highlight where defects or damage might be occurring when a painting is periodically photographed.

Camera monitoring a painting
Camera monitoring a painting in the conservation workshop. Painted by Lawrence, it went through a long conservation process and will be back to Brodsworth Hall in April.

In particular, this project aims to monitor the impact of conservation treatments known as lining, which are applied to the back of paintings to offer strength and support. Conservators need to understand the long term performance of such lining treatments on paintings that are on open display in historic house environments. Therefore, monitoring the structural health of an artwork, through a network of low-cost cameras, has the potential to provide sufficient information for conservators to take action in a more efficient way, before irreversible damage occurs to a painting.

Picture credits: English Heritage

Find out more about Conservation Science at English Heritage

 

 

All that glitters is not gold: technical examination of jewellery and gold brocade in a royal portrait attributed to Adrian Vanson

This next heritage science contribution to British Science Week 2017 comes from the Dr Caroline Rae at National Galleries Scotland and highlights some of the technical examination techniques that can be used to address questions about workshop practice and authorship of paintings.

Microscopy allows comparative examination of minute details of brushwork not normally visible to the naked eye. Examination of minute samples of paint can inform conservators about pigments, preparatory layers and paint layers. Dr Caroline Rae describes how these analytical techniques have illuminated the different materials and techniques used to create the illusion of jewellery and highly expensive cloth worked with golden thread on a portrait of James VI.

Great care has been taken to depict the gold brocade and the doublet worn by the king. Examination in microscopy suggests that at least three hands were at work in creating this painting. The looser, more confident style used to create the sitter’s face and cloak contrast with the more systematic techniques used to paint the hat-band and doublet. This is not unusual – it was common for artists in Europe at the time to have up to four studio assistants.

16_NGS_1 PG 156 overall recto.jpg
Attributed to Adrian Vanson., James VI, 1595, oil on panel, National Galleries of Scotland (PG 156) 72.90 x 62.30 cm

The artist who painted the doublet has very precisely painted in each individual thread using neat yellow strokes, as revealed in the photomicrograph.

16_NGS_2 PG 156_0013 doublet and belt alt.jpg
Vanson, James VI, photomicrograph (brushwork on the doublet and belt worn by the king)

In the paint sample taken from this area, it can be seen that lead-tin yellow pigment has been used to create the illusion of glimmering golden threads (this layer overlies a pale base coat for the doublet, a traditional chalk ground layer and a thin coloured priming layer which were used to prepare the panel support for painting). Additional decoration has been added in the form of red dashes, comprised red lake and vermillion.

16_NGS_3 PG 156 sample 2.jpg
Vanson, James VI, paint sample taken from the doublet, area of red/ golden brocade decoration

The artist’s technique has a laborious quality although the precise and stiff three-dimensional strokes are successfully mimetic in appearance. A different hand appears to have been at work in the creation of the jewelled hat-band. This artist combines precise, deft strokes with a freer application of paint, as revealed in the photomicrograph taken from this area.

16_NGS_4 PG 156_0026_detail of jewel0001 alt better.jpg
Vanson, James VI, photomicrograph (brushwork on the jewelled hat band worn by the king).

Monogrammed jewellery was popular throughout the sixteenth century, but reached its zenith during James’s reign when jewelled letters emblazoned with diamonds and rubies became the height of fashion at court, adorning garters, hat bands and brooches. The letter ‘A’ in James’s hat-band refers to his recent marriage to Anne of Denmark. The care taken to carefully represent these details in the painting reflects their importance within the composition in displaying the status of the king.

Caroline is the holder of the Caroline Villers Research Fellowship this year which is jointly hosted by the Courtauld Institute of Art and the National Galleries of Scotland. Caroline’s research focuses on the examination of portraits from the NGS collection attributed to Adrian Vanson and Adam de Colone, two Netherlandish artists who lived and worked in Scotland during the Jacobean period. Caroline is using well-established methods of technical examination, including microscopy and sampling, to examine questions of workshop practice and authorship in relation to both artists and to help build a better picture of workshop practice in Scotland. Click here for more information.