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Imaging of Varnish Layers Using OCT at National Gallery

Art, soft matter and SANS: combining optical coherence tomography and scattering methods for art conservation applications

  • School: School of Science and Technology
  • Study mode(s): Full-time
  • Starting: 2023
  • Funding: UK student / EU student (non-UK) / International student (non-EU) / Fully-funded


In this project, you will develop a non-invasive imaging system for the characterisation of layered structures in combination with neutron scattering techniques at the ISIS Neutron and Muon Source. In collaboration with the National Gallery, London and Tate, you will apply this powerful new imaging system to help solve pressing challenges in painting conservation.

Neutron scattering has enabled transformative research in heritage science, including ISIS’s recent contributions to elucidating ancient metallurgy techniques, inks on Egyptian textiles, or how environmental conditions affect painting canvases. Through application of cutting-edge imaging techniques like optical coherence tomography (OCT) and spectral imaging, Nottingham Trent University (NTU) has similarly revolutionised heritage science applications and recently won the Queen’s Anniversary Prize for Advancing Heritage Science.

This PhD, jointly offered through ISIS and NTU, is a timely way to combine the complementary strengths of OCT and neutron scattering techniques, for the first time, providing a unique new capability for simultaneous observation of the macroscopic and nanoscopic structure of soft matter.  The project will involve research work both at Nottingham Trent University, supervised by Lucas Goehring and Haida Liang, and the ISIS Neutron and Muon Source, supervised by Antonella Scherillo and Najet Mahmoudi, at the Harwell campus in Oxfordshire.

Paintings are artistic expression in soft materials. Their component layers of polymers, dispersions and emulsions are well-known to soft matter physics and ideal for small-angle neutron scattering. Although appearing static to a gallery visitor, paintings respond to their environment, changing appearance over decades. Preventive conservation mitigates against damage, while restoration attempts to return art to its original look. Scientifically, you will combine OCT and neutron scattering methods to address two of the most important challenges in the restoration of paintings:

Blanching involves irreversible damage to a painting by exposure to moisture, causing the varnish or paint to become cloudy or opaque. The effect results from the growth of nanoscopic pores, which scatter visible light. The appearance and evolution of these pores is suggestive of a phase separation process, working to minimise the interface between a hydrophobic varnish polymer and water that has infiltrated into its initially invisible pores.

Solvent invasion: Varnishing a painting brings out the colours and provides a protective layer. However, natural varnish degrades and becomes yellow and hazy with time, requiring replacing. For this, solvent is applied that invades and dissolves the varnish before it is reapplied. Understanding how solvents interact with layered paint-varnish structures is one of the most significant challenges in painting restoration.

Your contributions will be to apply joint OCT and neutron scattering methods to gain insights into varnish blanching and solvent invasion, informing restoration strategy.  For example, a key result of the blanching study will be a time-series of the evolution of the pore-size distribution.  Feeding into models of polymer dynamics, this will allow predictions of how blanching proceeds, and means of detecting damage before it becomes visible.  For restoration, OCT and scattering techniques offer complementary information about the solvent invasion, swelling and damage processes into layers of varnish and paint.

As part of your degree, you will also benefit from specialised training, such as the ISIS Neutron Training Course, the Oxford School on Neutron Scattering, and European Summer School on Scattering Methods Applied to Soft Condensed Matter and will have opportunities to work with and learn about modern conservation practice from National Gallery, London and Tate staff. At NTU you will have access to specialised training in non-invasive imaging techniques, including OCT, and a comprehensive training programme of transferrable skills aligned to the Vitae Researcher Development Framework, including e.g. media training and grant writing workshops. You will also have the opportunity to participate in the regular meetings and activities of the soft matter group and the Imaging & Sensing for Archaeology, Art history and Conservation (ISAAC) group (

Entry qualifications

The applicant should hold a first or upper second class honours degree from a UK university or an equivalent qualification, or a lower second class honours degree with a master’s degree at Merit level from a UK university or an equivalent qualification. Your degree should be in a relevant area of science and technology, such as physics, engineering or maths.

Overseas applicants may also be required to meet English Language requirements as a condition of any offer.

How to apply

The deadline for this project is Monday 22 May 2023 at 11:59pm.

For a step-by-step guide and to make an application, please visit our how to apply page.

Interviews will take place in early June.

Fees and funding

This is a fully-funded (stipend plus UK/Overseas tuition) 4-year PhD project, with funding provided jointly from NTU and the ISIS neutron and muon source.

Guidance and support

Further guidance and support on how to apply can be found on our apply page.

Still need help?

Lucas Goehring
+44 (0)115 8483814