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.

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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.

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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.

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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.

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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.

Eight million photographs: how can science help? – Jacquie Moon, the National Archives

As part of British Science Week 2017 the National Heritage Science Forum is featuring blog posts from heritage scientists from across its member organisations. This year’s theme is ‘sharing heritage science’, and the blogs over the rest of the week will give an insight into the many different forms that heritage science can takes, as well as some of the different ways of getting involved.

Jacqueline Moon is the Senior Conservator for Public and Academic Engagement at the National Archives. She specialises in the conservation of photographs. In this blog, Jacqueline describes how she is using science to care for the photographic collection with the help of volunteers.

The National Archives’ collection includes approximately eight million photographs. The subjects are varied, and include Victorian and Edwardian photographs from the 1850s; of Eccles cakes, circus performers with boa constrictors, ‘the oldest lady in bed’, children acting out barber shop scenes and the Titanic. Later collections include the more serious Operation Sandstone, a unique survey of the British coastline which began in 1947 to help NATO forces plan a re-invasion in case the country was taken over by communist forces.

Their sensitivity to moisture and pollutants poses unique challenges for preservation and conservation. To understand these collections better, the Collection Care department at The National Archives’ is doing a survey with the help of volunteers, who have been trained to identify photographs and understand their deterioration. Their observations are helping us prioritise conservation projects, improve storage and use science to build a more accurate picture of the collection. Without their help it would be impossible.

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A cross-section of a silver gelatine photograph on fibre-based paper

Silver gelatine photographs are prone to mirroring (a bluish reflective sheen seen in the shadow areas), yellowing and fading. This is because of changes to the image silver which can be caused by high relative humidity, pollutants or poor processing. Experts claim to be able to look at a deteriorated photograph and tell the causes; an image affected by high humidity would have a more yellowed appearance but an image which has been poorly processed would look more orange brown.  

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Top: A well processed test photograph partially aged and the same photograph at x150,000. Below: A poorly processed test photograph partially aged and the same photograph at x150,000.

The photograph conservator at The National Archives undertook research into the deterioration of silver gelatine photographs, the commonest type in the collection, to find out if a simple colour measurement by non specialists could help make conservation decisions, such as prioritising certain items for cool storage and selecting others for the exhibitions and the loans programme. A number of scientific techniques were used to study a set of laboratory made and historical photographs. The techniques included spectrophotometry (a method for quantifying colour), transmission electron microscopy (effectively a microscope but instead of light and lenses it has electrons and electromagnetic fields) and spot tests to test for impurities 

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Taking colour measurements of a series of sample photographs

The colour measurements showed that photographs affected by poor processing had red and purple hues, whilst transmission electron microscopy showed they had clumped image silver; those affected by high relative humidity were more yellow but had lots of spherical silver particles, called colloidal silver (see image 2)

The next steps are to prove this on a larger scale so it could be used more widely; testing records affected by yellowing using information gathered during the survey. Volunteers will be trained to collect and interpret the colour data and the results will be publicised in due course. If you’d like to read more about how we care for the photographic collection at The National Archives, you can read our blog here.

Private Space on Public View: Dust Monitoring for the Eduardo Paolozzi studio at the National Galleries of Scotland

As part of British Science Week 2017, the National Heritage Science Forum is once again featuring blog posts from heritage scientists from across its member organisations. This year’s theme is ‘sharing heritage science’ and the blogs over the rest of the week will give an insight into the many different forms that heritage science can takes, as well as some of the different ways of getting involved.

After yesterday’s post about the London shipwreck, today’s article looks at Arielle Juler’s dust monitoring project for the Eduardo Paolozzi studio at the National Galleries of Scotland…

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View into the Eduardo Paolozzi studio from the visitor barrier

Arielle Juler is currently undertaking a Preventive Conservation MA degree with Northumbria University. As part of her dissertation research, she is looking into the preventive conservation plans and methodology available for the preservation of artists’ studios on public display within gallery spaces. Using the methodology established by the National Trust for dust monitoring in historic houses, she’s conducting a low-technology dust monitoring project. The monitoring method uses slide mount frames and clear adhesive labels to trap dust as it falls on the slide. The rate of deposition is then measured against a graph paper and percentage coverage can be estimated. The percentage estimations can be compared and inform the rates of dust deposition and how/where dirt enters the studio space.  

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Dust trap in situ within the Eduardo Paolozzi studio
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Arielle Juler examines dust slide within the Eduardo Paolozzi studio

The dust monitoring project started in September 2016 and is ongoing through April 2017. The project will provide baseline information on the rates and levels of dust deposition on the objects within the studio space. Currently it is not known how quickly the studio becomes dusty or where the dirt is entering the studio space.

The National Galleries of Scotland will be able to use the data gathered from the monitoring project to establish a conservation plan and cleaning schedule for the studio space. This will in turn assist in the preservation of the artist’s materials and ephemera on public display.

Contact the Conservation department at the National Galleries of Scotland: conservation@nationalgalleries.org 

Historic England – Conservation of artefacts from the ‘London’ shipwreck

As part of British Science Week 2017, the National Heritage Science Forum is once again featuring blog posts from heritage scientists from across its member organisations. This year’s theme is ‘sharing heritage science’ and the blogs over the rest of the week will give an insight into the many different forms that heritage science can takes, as well as some of the different ways of getting involved.

Next up is a post by Dr. Eric Nordgren of Historic England, talking about the conservation of artefacts on the wreck of the 1665 London ship…

The London was a Royal Navy warship that sank in the Thames Estuary following an explosion in 1665. A program of work to better understand this protected shipwreck has been underway since 2014, resulting in surface recovery of exposed objects and in two seasons of underwater excavation and recovery of hundreds of artefacts made of wood, leather, rope, ceramic, glass, iron, copper and lead. The LondonWreck1665 project is a collaboration between the protected wreck licensee, maritime archaeologists from Cotswold Archaeology, scientists and conservators at Historic England’s Fort Cumberland site in Portsmouth and the Southend Museums Service, where the artefacts and scientific data will be deposited.

The goals of conservators working on the London material are to assess the condition of the artefacts and apply investigative and remedial conservation techniques to make them as stable as possible for study and display at Southend Museums while learning as much as possible about the materials they were made from, how they were produced, and their working life on-board ship. The conservation process offers lots of opportunities to collaborate with specialist scientists to gain information such as the species of wood used to make artefacts such as musket powder cartridge bottles, the type of fibres used in rigging and cordage or the elemental composition of glass and metal finds. All of this adds to our knowledge of 17th Century seafaring and life on-board the London in particular.

All materials change and as conservators we try to understand these changes and slow them down. Iron artefacts for example often develop a thick coating of rust and marine growth called ‘concretion’ that can hide their true shape. Conservators use X-radiography to get a closer look inside the objects. These X-rays help conservators plan micro-excavation of concreted artefacts in the laboratory or can sometimes reveal the shape of objects which are no longer preserved.

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Photo (left) and digital X-radiograph (right) of an iron artefact from the wreck of the London. The object is covered by rust and concretion but radiography allows conservators to look inside and see the original size of the iron ring and how much metal still remains. (Images: Historic England 2017)

 

Conservators working on London artefacts use a variety of scientific principles and analytical techniques in their daily work. An example is the monitoring of salt removal (or desalination). Both organic (wood, leather) and inorganic (ceramics, glass, metal) materials can be damaged if allowed to dry out while they still contain soluble salts such as sodium chloride. Artefacts are soaked in baths of distilled water which allows salts to diffuse out, allowing them to be safely dried.

Some objects such as a cast iron cannon ball can’t be desalinated effectively using distilled water alone. For marine iron, 0.5 Molar sodium hydroxide solution in distilled water (pH 13.5) is used to extract chlorides more effectively. The concentration of chloride salts measured in parts per million (ppm) in the desalination bath is monitored weekly, allowing us to track chloride release, determine when the bath needs changing and when the treatment is finished (normally when very low levels of chloride are detected in solution).

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Graph showing concentration of chloride extracted (in parts per million) from a cast iron cannonball from the London into a sodium hydroxide (NaOH) desalination solution over 50 days. The concentration reaches 550 ppm after about 35 days, indicating it is time for a fresh desalination bath. (Images: Historic England 2017)

The Historic England conservation team working on the London at Fort Cumberland, Portsmouth includes Angela Middleton and Eric Nordgren.

Find out more about the London by following #LondonWreck1665!