Color standards

I am looking for a color standard, specifically a ceramic tile that
is used for calibrating colorimeters.  I think they are available in
4 inch squares, and I know they come in white--they might also come
in different colors. Does anyone know what these are, and where I
can get one?

Judy Jacob
Senior Conservator
National Park Service
Northeast Cultural Resources Center
Building Conservation Branch
212-825-6877


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                  Conservation DistList Instance 15:75
                   Distributed: Tuesday, May 7, 2002
                       Message Id: cdl-15-75-009
                                  ***