October 1993 Issue 09
WARP (wooden artefact rheology project)
As a venue for major international exhibitions the Victoria & Albert Museum is being asked to provide environmental conditions to increasingly tight specifications, sometimes beyond the accuracy of current electronic equipment. Providing very tight environmental control, especially in an exhibition space, is technically difficult and very expensive. If total stability cannot be guaranteed then we must decide how much variation can safely be allowed. How good is good enough?
Changes in relative humidity of air lead to changes in moisture content of hygroscopic materials such as wood; this leads to dimensional and physical change. Alterations to the dimensional and physical properties may cause damage to sensitive areas particularly wooden supports or paint layers. Therefore it is necessary to err on the side of caution in specifying a suitable stable environment for the display of such objects. Tight stipulations progressed from the assumption that the stability of objects is directly correlated with the stability of the environment. However, this, as a rule of thumb is not infallible. Even very small changes may sometimes be disastrous whereas many objects may tolerate larger changes.
Therefore it is appropriate to examine more carefully interactions between objects and their environment in order to minimise the risks. An opportunity for running an experiment in actual display conditions with comparable objects has been provided by the exhibition 'Gates of Mystery: The Art of Holy Russia'. The exhibition contains many large wooden icons including such famous medieval treasures as the fifteenth century icon of St George and the Dragon.
WARP (Wooden Artefact Rheology Project) was set up with assistance from Exhibition funds to fulfil two purposes. Firstly, to measure very small changes in the dimensions of a wooden panel to see if these could be correlated with changes in relative humidity. Of particular interest is the extent of dimensional change that may take place during short periods when environmental conditions deviate from specified values. Secondly, in the longer term, to investigate in detail the relationship between relative humidity, moisture content and dimensional change.
A mock icon has been prepared in a similar manner to those in the show. During the Gates of Mystery exhibition, this panel will be in a case within the exhibition hall under conditions equatable to the icons on display. Movement of the panel will be measured by two gauging transducers1 chosen for their quick response to changes of a few microns over a 10mm range. These are being interfaced with radio telemetry equipment2 that is currently used in the Museum. During the exhibition, measurements of relative humidity, temperature and strain will be transmitted by radio at 30 minute intervals to the Conservation Department's Science Group laboratories. It will then be possible to display data graphically to show fluctuations in these three parameters.
The information obtained from this and related experiments will be used to optimise the protection provided by exhibition displays for environmentally sensitive objects.
We are grateful for the assistance and cooperation of the Exhibition and Design Sections in helping us to carry out this work.