Visual Perception of Soiling on Vertical Surfaces

Stuart Adams¹, Richard Kibrya², Peter Brimblecombe³ & Carlota Grossi³

Dept. of Chemistry , Queen Mary University of London, United Kingdom ¹
Victoria and Albert Museum, United Kingdom ²
School of Environmental Sciences, University of East Anglia, United Kingdom ³

To investigate colour change on vertical textile surfaces due to particle deposition, selected modern textiles were suspended in museum galleries at the Victoria & Albert Museum. Assessment of the deposition of particles on the cloth surfaces was by measurement of colour coordinates prior to exposure and thereafter at three monthly intervals. A graded dot matrix was created with proprietory software and printed on an A3 sheet of paper with scale of 0 - 100 along the base. The point at which dustiness was perceived by a sample of museum visitors was determined by moving a cursor along the scale veiwed in a standard light box.. The colour coordinates were measured for the range of these points. When the survey results equal that of the test materials it is suggested necessary to clean. Surface area and moisture content of the test materials were also measured.

Location	Calculated Colour co-ordinates DE	Conditions
Tapestry	0.81	Air conditioned, low visitor numbers, enclosed room
G98	1.54	No air conditioning, moderate visitor numbers
G100	2.30	No air conditioning, high visitor numbers
G55 Stoke Edith	1.61	Air conditioned, high visitor numbers
Greyscale at 80mm	18.01

Table 1: Comparison of DE readings for cloth strips (after 10 months) and the greyscale survey result

Results to date:

1. The perception survey where people were asked to estimate the point at which they could perceive dustiness on a greyscale has been extended. The new graph (fig.1) now emphasises the area about 80mm from the white end of the card. Consequently the original bi-modal response distribution has diminished.
   
   
2. Colour co-ordinates have now been measured at the 80mm area (+/- 2mm).
   
   
3. Summary: After ten months exposure there are significant differences in the readings from the cloth test strips which reflect the different environmental conditions, ie air conditioned or not and the quantity of visitors.
   It is estimated that the exhibits in G100 would require conservation after 7-8 years and the remaining galleries somewhat longer. It is intended to expand the greyscale survey to obtain a better public response to soiling tolerance thresholds.

Part 2: Slides from presentation

Author to whom correspondence may be addressed:

Stuart Adams
Dept. Chemistry
Queen Mary University of London
Mile End Road
London E1 4NS

E-mail: s.j.adams@qmul.ac.uk