Blue wool scales

In CDL 7:18 Shirley Rodnitzky asked for interpretative date re: blue
wool fading strips.

The British Standards Institution has published BS 1006:1978 (date of my
copy) _Colour fastness of textiles and leather_, and a _Grey Scale for
Assessing Change in Colour_.  These should be available from BSI, 2 Park
Street, London, England  W1A 2BS (again, a 1978 address).  I believe
that I purchased my set through Joel Frank, Ltd.

The slide rule/grey scale is very important, in that a quantitative
evaluation of light absorption is based on a change in the blue wool
fading strip approx. equal to the difference between two shades of grey
on the grey scale.  Without the grey scale, the blue wool fading strips
are of anecdotal value only.

Jack C. Thompson

                                  ***
                  Conservation DistList Instance 7:21
                  Distributed: Friday, August 20, 1993
                        Message Id: cdl-7-21-001
                                  ***