Conservation Scientists' Group Meeting: Accelerated Light Ageing

Graham Martin
Head of Science, Conservation Department

Another successful and popular meeting of the Conservation Scientists' Group was held at the Tate Gallery, London on Wednesday 23rd February 2000. The particular topic of discussion for this session was 'Accelerated Light Ageing in the UK' - an all day meeting with the morning session dedicated to presentations from eight users of light ageing  equipment. The afternoon session was given over to open discussion on the topics raised in the morning session.

Participants attended from across the UK with an obvious bias towards the London based groups due to the ease of travel. Thirty six delegates were registered to attend. The titles of the morning presentations had a remarkable resemblance to each other in that they all followed the format of 'Accelerated light Ageing at …….' and one could fill in the name of the various institutions. However, this uniformity of title did not reflect the varied content.

The host organisation made the first two presentations with Joyce Townsend (Tate) describing the history of the subject at that organisation and the reasons for undertaking such testing. Christina Young (Tate  and Imperial College) followed with the work of the team concerned with the mechanical deterioration of paintings and introduced the fundamental question of the need to control temperature and relative humidity. René Hoppenbrouwers (Stichtung Restauratie Atalier Limburg, Maastricht) described a bespoke light ageing chamber designed specifically to answer the queries raised from the MOLART1  Dutch project - a unit derived from a wine storage system. Alan Phenix (Courtauld Institute of Art) covered the reasons why it is necessary to undertake accelerated light ageing and these may be summarised as follows:

  •  to evaluate durability
  •  to investigate mechanisms of decay
  •  to prepare appropriate aged material.

Alan also highlighted the practical difficulty of undertaking light ageing experiments in the student context where there are very fixed deadlines and often short time periods in which to complete the work. The next presentation was from David Saunders (National Gallery, London) describing the different models of light box that have been used at the National Gallery - how each successive model achieved its target of bringing the exposure temperatures down to a more realistic and acceptable level. Vincent Daniels (British Museum) also presented the progression through the different models of light box used but he also introduced material other than painted/pigmented film to the meeting in the guise of 'Peat Bog Man', paper bleaching and coin corrosion issues. The Bullerswood carpet fading experiments were presented by Boris Pretzel (V&A) giving experimental detail and some early results of the micro-fading process. Marianne Odlyha (Birbeck College) presented the EU funded Environmental Research for Art Conservation project and the damage dosimeters that this team were preparing for general usage.

The afternoon session was dedicated to open discussion. In particular the following key points were tabled:

  • UV versus UV filtered light source
  • Temperature control
  • RH control
  • Pollutants
  • Illuminance measurements
  • Commercial production of a suitable unit

Without giving a detailed account of the discussion, the outcomes can be summarised as follows:

  • It is easier to design a system that includes the UV portion of the spectrum and then add filters to remove it if not required
  • Temperature control - no agreement on set point could be reached but some means of control was essential
  • The discontinuance of the Blue Wool standards from the Society of Dyers and Colourists could cause difficulties
  • A standard dark time after light exposure would be preferable - no agreement was reached on the actual dark time
  • An appropriate range of suitable lamps could help to establish conformity within the community
  • A round robin series of tests to establish system comparison should be undertaken

I formed one opinion in particular during the day concerning  the use of accelerated light ageing apparatus. Only the British Museum presentations  and the V&A presentation dealt with media other than paints or films. I appreciate that it is in the area of pigments that light damage is of concern but the British Museum presentation dealt with possible corrosion processes caused by, or accelerated by, light. Any apparatus that we do come to some agreement on should be capable of use for these other materials.


References

 1. Molecular Aspects of Ageing in Painted Works of Art: MOLART is a 5-year co-operative project between art historians, restorers, analytical chemists and technical physicists funded by the Netherlands Organisation for Scientific Research (NWO). The object of MOLART is the development of a scientific framework for the conservation of painted art on the molecular level.