AIC's 46th Annual Meeting

For centuries, lead based paints have been the primary paints used on external woodwork on historic houses. However, recent changes in legislation related to VOCs (volatile organic components) and the restriction of the use of lead paint due to toxicity has meant that paint formulations have changed to meet the changing legislation requirements. In addition, there has been a growing interest in the use of "environmentally friendly" paints. For historic houses, the cyclical maintenance requirements of repainting external woodwork is a major financial consideration and as result, the need to assess the performance of the wide variety of paints available encouraged the National Trust to undertake a series of paint trials to assess sustainability as well as consideration of the visual appearance of the paint (a factor which is important in maintaining the historic appearance of our properties). In 2006, the National Trust began a series of external paint trials on 13 garage doors on one of our properties to assess the performance of the selected paints. The trials provided information about the sustainability of the paints based on visual evidence of cracking, flaking, color change and moisture penetration. Whilst informative, it was realized that the results could not provide a recognized methodology for comparing the paints' performance. As a result, a group of heritage organizations led by the National Trust decided in 2011 to conduct a series of trials at the Paint Research Association in order to provide an industry recognized standard testing procedure to assess 34 paints which were selected on the basis of those used by the members of the group as well those which were commercially available to ensure that they would still be available after the conclusion of the trials. In addition, a number of "environmentally friendly" paints were included to assess their performance. The trials began in 2012 and after four years of testing, the results enabled the group to evaluate the performance of the paints and select 10 paints which performed above average as well as a linseed based paint, a lead based paint and a ICP (internal comparison product used as a standard) to be used to coat a number of the original panels to assess their performance. It was felt that this test would reflect more accurately the method of repainting used on historic properties where the underlying paint layer is simply sanded to remove defects and then coated with a new paint layer. It would also provide information about the sustainability of applying a different paint system over an existing paint layer. This paper explains the procedures involved and the results to date which should provide guidance for historic properties to ensure that the most sustainable paint systems are applied to external wood work.