Comparison of visual assessments for colour fastness among three countries and the relationship between the visual and the instrumental assessment

In a previous report, we examined the difference between the visual assessment of Japanese and Thai observers for colour fastness. A significant difference between two countries was found. Therefore, it is very important to examine whether the same tendency exists for other countries. In this report, data of Hong Kong were included in addition to those of Japan and Thailand. We carried out the same experiment as the previous one and compared the results of the visual assessments among the three countries. The properties of the visual assessment in each country for staining and change in colour were obtained. Because the difference among individuals and countries can not be avoided in the visual assessment, the instrumental method is more desirable, and the several objective methods have been proposed. We examined the relationship between the visual assessment of each country and the instrumental assessment. When comparing the visual assessments to the instrumental assessments for each of the three countries, the differences are greater than those between visual assessments of any two countries. Therefore, if we could develop a formula fit well using data from a country, it would be possible for this formula to be used in the other countries. From the results obtained in this study, we suggest the use of the instrumental assessment method instead of the visual assessment. Thus, the dependency of the colour fastness assessment on the individuals and countries can be avoided.