MÄTA FÄRGFÖRÄNDRINGAR PÅ PLAN TEXTIL En litteratur- och experimentstudie

Abstract

In this thesis, the use of portable colorimeters for monitoring color-change on textiles on display in a museum environment are examined. The idea for this study developed from the author´s time as an intern at Nationalmuseum in Stockholm, Sweden. The conservators working at the museum have been thinking about this problem in light of the museum’s re-opening scheduled for autumn 2018 where daylight will be a part of the lighting system in the museum. A literature study was conducted of earlier studies about lighting in museum environments, and why color change occurs in textiles, as well as in the color measurement field. The literature study leads in to the experimental part of the study where two types of colorimeters were evaluated. These are: a spectrodensitometer with 45o/0o geometry and a spectrophotometer with the geometry d/8o. For the d/8o geometry, the specular component included (SCI) respectively the specular component excluded (SCE) mode were also be taken into consideration in the evaluating of the colorimeters. To evaluate the two different colorimeters, samples will be prepared in a light-aging experiment. The experiment is simulating five years in a museum environment with 3 000 opening hours and with a 50 lux illuminance per year, giving it an annual illuminance of 150 000 lux hours. So the samples were illuminated to a total illuminance, for five years, of 750 000 lux hours. The samples consist of three categories: wool-samples dyed with known natural dyes, surrogates which imitate flat textiles that a museum would put on display, and lastly a Blue Wool Standard. In the evaluation, the difference in CIE L* a* b* and colour-difference, represented by ΔE (delta E), values between the spectrodensitometer and the spectrophotometer where examined. Further, the importance of direction of the sample was studied by calculating the ΔE value for measurements of different directions, with 90o difference, of the samples. The study showed that a handheld colorimeter might has the potential to be a useful instrument for in situ preventive conservation in the aspect of objects color-change in a museum environment: though, many parameters must be taken into consideration, such as direction of the textile and measuring point. Further research is needed for a more accurate evaluating of the colorimeters usefulness in color-measuring on flat textiles.