Cleaning Modern Oil Paints Project

Tate is the newest recipient of the NHSF Gold Open Access grant for the publication of heritage science research. The grant enabled the publication of the research paper Scientific investigation into the water sensitivity of twentieth century oil paints’, available for free in Microchemical Journal. In this guest post, the paper’s authors tell us more about the Cleaning Modern Oil Paints project.

The Cleaning Modern Oil Paints project (CMOP) is a collaborative European research project, funded through the JPI Heritage Plus programme, which runs from June 2015 – May 2018. The project aims to investigate conservation challenges associated with twentieth and twenty-first century oil paintings in order to ensure that modern oil paintings continue to be fit for display for future generations.

Many unvarnished twentieth and twenty-first century oil paintings are exhibiting unusual water sensitivity. Water sensitivity can be defined as the unwanted removal of pigment and/or original material when a discrete cleaning test is carried out using a dampened cotton swab on the surface of a painting. Water sensitivity is not restricted to a particular oil-paint brand, or artist, and affects a broad range of paintings.

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Winsor & Newton Artist Oil Colour swatches that were studied as part of the microchemical journal paper. Copyright Tate.

Water sensitivity is problematic for conservators, since many of the well-established methods for removing surface dirt (which naturally gathers over time) involves the skilled application of water based cleaning systems.  Since dry-cleaning methods, for example using dry brushes or specialist sponges, are not always particularly effective at removing soiling, water sensitivity can complicate or even prevent effective treatment. This is problematic as accumulated surface dirt can change the appearance of paintings e.g. through altering the saturation, intensity and gloss of paint passages, and can, over the longer term, contribute to other unwanted side-effects relating to ageing and deterioration.

The interdisciplinary CMOP team have been investigating the underlying causes of water sensitivity in modern oil paints. This information has been used to inform the systematic testing and evaluation of selected cleaning systems for use on water sensitive modern oil paintings, with the aim of informing conservators about the risks involved and how to minimise them.

Part of the CMOP research has involved the chemical analysis of a series of naturally aged modern oil paint micro-samples, taken from case study oil paintings and from historic Winsor & Newton (W&N) artists’ oil paint swatches.  The W&N paint swatches were originally produced by the manufacturer for quality control testing, and were subsequently donated to Tate by ColArt UK for research purposes.

W&W Artist Oil Colour swatches studied for the paper, shown in tungsten light (left) and UV light (right). Copyright Tate.

We are pleased to announce that the National Heritage Science Forum has kindly sponsored the Gold Open Access publication of a key CMOP research paper, entitled Scientific investigation into the water sensitivity of twentieth century oil paints, now published in the peer-reviewed Microchemical Journal. This describes an in-depth investigation into the chemical characteristics of water sensitive paint passages, and likely causal factors.

The research at Tate is led by Principal Conservation Scientist Dr Bronwyn Ormsby, with Post-doctoral Researcher Judith Lee, and with the support of Tate’s Collection Care Research. More information on the project and details of the key CMOP project dissemination event; Conference on Modern Oil Paints taking place on 23-25 May 2018, are available on Tate’s website.

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Detail of a case study oil painting analysed as part of the project. Copyright Tate.

 

The paper Scientific investigation into the water sensitivity of twentieth century oil paints is co-authored by Judith Lee and Bronwyn Ormsby of the Tate Conservation Department, Ilaria Bonaduce, Francesca Modugno, Jacopo La Nasa and Klaas Jan van den Berg.

The National Heritage Science Forum provides Gold Open Access grants to help to open up access to heritage science research. This funding is available to employees, students and members of our member organisations – find out more.

A day in the life of heritage science students at Hellens Manor

Our final guest post for British Science Week 2018, #BSW18, comes from Gavin Leong, a student on the SEAHA MRes course. In this post Gavin reflects on the SEAHA cohort’s visit to Hellens Manor, which took place earlier in British Science Week, to analyse paintings using hyperspectral imaging techniques and carry out environmental monitoring and risk assessments that will inform future approaches to collection care.

Every year, a new roster of Masters students from EAHA visit a lovely old country house sat in scenic Herefordshire. But, far from a holiday or a retreat, these students are here to carry out research. And this isn’t any old house, it’s one of the few surviving 12th century English abodes, Hellens Manor.

Today is Tuesday 13th March 2018, it’s 9.25 AM and the sun is just peeking out of the clouds over Hellens. The imaging group are about to head out to Bloody Mary’s room, a place said to be haunted. But instead of looking for paranormal activity, for the past two days they’ve been painstakingly taking images of paintings using multispectral imaging and infrared reflectography. The former was used as a rapid survey of the ultraviolet, infrared and visible spectrum, while the latter can reveal underdrawings.

With the camera equipment, lighting and cables strewn across the floor they resemble a film crew on the set of a period drama. The stars in this production are two paintings, on canvas and panel. Today, however, they will be using hyperspectral imaging to analyse areas of the paintings with similar composition and pigmentation, which can highlight more modern modifications to the paintings.

It’s now 11.35 AM. The environmental monitoring group are taking advantage of the abundant sunlight, a welcome respite after the recent bout of heavy snow and rain. They’re in the stone hall, where you can find an impressive fireplace that bears the crest of Edward, the Black Prince. But their eyes are drawn to the two equally compelling tapestries. One half of the team are thermal imaging, and measuring the UV and intensity of light falling on the woven fabric, while the other half are assessing its condition using a handheld microscope.

Image of thermal imaging at Hellens Manor by SEAHA students
Thermal imaging at Hellens Manor by SEAHA students

 

Image of condition assessment of tapestry at Hellens Manor using a handheld microscope
Assessing the condition of a tapestry at Hellens Manor using a handheld microscope.

Later, they’ll be setting up a camera for digital image correlation to observe any deformation or small changes in strain of the tapestries. By correlating these changes with measurements of fluctuation in humidity, temperature and light in the room, it could contribute to recommendations on best practice for conserving the tapestries in the stone hall.

On any other day it would be difficult for any passing observer to spot the risk assessment group. But not today. It’s 3.17 PM and they’ve donned bright yellow disposable overalls and face masks for the sake of heritage science. Dubbed ‘Minions’ by one of their group members, they have the unenviable task of crawling under the Munthe ‘Cinderella-style’ dress carriage built in the 1860s to get to the back wall of the coach shed. But it was not in vain: there they find the elusive mould, predicted by the humidity and moisture assessment, on the red silk.

Image of looking for mould at Hellens Manor
Looking for mould at Hellens Manor

The carriages had not been assessed prior to the work by the team. With the fibre and pest identification, moisture content survey of the wood and corrosion assessment of the metal, the risk assessment group can present a strong case for the future management of the carriages.

Image of pest identification
Pest identification (carpet wool larvae)

To find out more about studying Heritage Science at the EPSRC Centre for Doctoral Training in Science and Engineering in Arts, Heritage and Archaeology, visit the SEAHA website. The Centre is currently advertising several studentships with mid-April application deadlines.

 

Advanced imaging technologies uncover hidden details on Rubens paintings

Next in our British Science Week 2018 series, Historic Royal Palaces’ Senior Conservation Scientist Dr Constantina Vlachou-Mogire tells us about investigating the Rubens ceiling paintings at Banqueting House…

Historic Royal Palaces is preparing for the 400th anniversary of the Banqueting House, which will take place in 2022. During this major project we have a rare opportunity to access and study in detail the Rubens ceiling paintings, their fabrication technique and current condition.

The Banqueting House is the last surviving building of Whitehall Palace which was destroyed by fire in 1698 (Figure 1). Set within a decorative coffered ceiling designed by the building’s architect, Inigo Jones are nine paintings by Rubens, the artist’s largest and most accomplished works to remain in the context for which they were designed. The paintings were commissioned in about 1629 by Charles I as a testament to the glory of the Stuart monarchy through the depiction of his father James I’s life and achievements.

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The Main Hall at Banqueting House

These internationally significant paintings are an integral component of the architecture of the hall. Originally the Banqueting House Rubens ceiling paintings were oil-on-canvas stretched on strainers, but since 1907, they were attached to plywood boards. During their long history the paintings have been restored nine times—including in 1940 when they were cut up to evacuate the gigantic panels from the building.

High-resolution multi-spectral imaging

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Figure 2: Details of the multispectral gigapixel images of The Apotheosis of King James I panel (a. visible light, b. infrared reflected, c. ultraviolet-induced luminescence)

The first phase of our project involved capturing the condition of the paintings in high resolution images (Figure 2). The scale of the paintings, covering a total surface of 243 m2, and their position 17 m from the ground, made this task particularly challenging; however, recent advancements in digital photography helped us to overcome these difficulties.  Collaboration with imaging specialists developed the application of GigaPan technology to document all nine paintings from the ground in visible light and infrared light as panoramic ‘Gigapixel’ images. Ultraviolet-induced luminescence images were taken at close-range from a scaffold, by illuminating small sections of the painting and later stitching the images together to full-painting size. Superimposing the visible, infrared and ultraviolet images allows analysis and detailed classification of the current condition of the paintings as a standing record. This will underpin further investigations and inform the programme of conservation of these important paintings.

We would like to thank the following external collaborators for their expert insights and contributions to the successful progress of this cross disciplinary project: UV/IR imaging Dr Giovanni Verri (Courtauld Institute of Art) and Steven Paine (Paine & Stewart), 3D laser scanning, visible ‘Giga’ imaging John Hallett Jones (Glanville Consultants).

Five minutes with…Dr Lora Angelova, Newton International Fellow, University College London

What’s your background in heritage science?

I obtained a PhD in chemistry from Georgetown University, but focused my research on heritage science by having joint supervisors – professor of chemistry Richard Weiss at the university, and heritage scientist Barbara Berrie at the National Gallery of Art, Washington, D.C. The focus of my work is to develop and study gel cleaning systems used in conservation treatments. Gels are sometimes used during the surface cleaning of a myriad of heritage objects (paintings, frames, sculptures, even paper). The idea is that by holding the cleaning liquid in a thick gel, the cleaning action can be more ‘controlled’, i.e. the liquid is less likely to penetrate into the artwork, or spread and drip on the surface (if the artwork is vertical). Gels can also be used to reduce the risks posed by rubbing a sensitive surface with a cottons swab during cleaning (for example, on gold leaf decorated frames), and to clean hard to reach places, like crevices beneath paint impasto.

What’s your role at the Materials Studies Laboratory at UCL?

I am in the second year of my Newton Fellowship (a postdoctoral fellowship awarded by the Royal Society to external researchers who would like to work in the UK). I work with Emma Richardson in a laboratory on the top floor of the History of Art Department – we are the only scientists in the department! It’s a very different environment from working in a chemistry lab, and I really love it.

There are a few instruments here, but the one I am primarily using in my research is called an NMR MOUSE (Nuclear Magnetic Resonance, Mobile Universal Surface Explorer). The instrument allows me to look into paint films, and trace how liquids from different types of gel cleaning systems move into the paint. I am studying several gels which are used by conservators and hoping to clarify how much ‘control’ of the cleaning liquid they actually present, relative to just using a cotton swab wetted with the cleaning liquid.

NMR MOUSE
The NMR MoUSE (the tiny black box on the blue platform), in the process of scanning a paint-out which has just been treated with a gel.

 

What’s been the most exciting/challenging thing you’ve worked on recently?

Last year I worked with a conservator who was treating a painting which had been largely overpainted centuries after its production. The overpaint film was very stiff and had extensive craquelure – when he tried to soften the overpaint with a wetted cotton swab, the cleaning liquid would be drawn through the cracks into the original, sensitive paint layer beneath. We were hoping that by using a gel, we could slow this process, and soften and remove just the tough, top layer of overpaint. Although the gel did allow some control and prolonged exposure of the overpaint to the cleaning liquid, it was not sufficient to soften it without having some of the liquid penetrate through the cracks to the original paint beneath! The treatment was incredibly challenging, and the conservator opted to use a gel on some areas and cotton swabs on others.

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Applying a fluorescent gel to a test-panel during my PhD – the fluorescent solvent can help us trace its penetration into the paint.

 

Who inspires you?

I really admire competitive and determined people who are passionate about what they do, both in their professional work and in their hobbies, especially if they’re women.

What do you love most about your job?

I get to combine the two things I was always most interested in as a child – science and art. I can make paint-outs in the morning and study their chemistry in the afternoon. I can look at the topography of a painting through a microscope – which feels almost like looking at the surface of the moon to me. Being a scientist can be demanding, of course, but as an academic, I get to choose what research I pursue, at what time I come in and leave work, and what the radio is playing in the lab. To top it off, I get to work with a very diverse group of people – conservators, art historians, artists, and scientists from a very wide range of disciplines.

In a single sentence, tell us what’s great about heritage science.

There is an inexhaustible supply of fascinating questions and problems to explore, and there is always a clear application which makes my work feel really worthwhile.