Pavement mosaics

Karen Fix <kfix [at] getty__edu> writes

>We are working on a project involving pavement mosaics (limestone)
>where the surface has roughened over time and resulted in a loss of
>color brilliance. The maintenance crew currently tosses a bucket of
>water over the surface to enhance the colors; this, of course, is
>adding to the normal deterioration mechanisms of the mosaic.  As an
>alternative solution, we are considering applying a coating with an
>appropriate refractive index, which would then conceivably smooth
>the surface enough to reduce the reflectance and allow the colors to
>appear darker.

I would be very wary of applying surface coatings to mosaics whether
they be in an internal or external environment. Changes in
temperature and humidity will lead to soluble salts crystallising
beneath the coating causing  spalling of the surface of the
tesserae. Obviously the buckets of water will mobilise the soluble
salts to an even greater extent. Surface coatings with a low Tg will
also attract dirt and darken the mosaic necessitating a time
consuming and probably damaging operation of removing and reapplying
the coating. It is the best policy for the mosaic to accept the loss
of brilliance as a natural consequence of previous abrasion and time
and  not to apply any coating and. If they  want to show  the
previous brilliance of the mosaic why not have an interpretation
panel explaining the process of deterioration and an illustration of
the former appearance and colours of the mosaic.

Val Munday
Freelance Conservator specialising in mosaics

                                  ***
                  Conservation DistList Instance 12:63
                 Distributed: Monday, February 1, 1999
                       Message Id: cdl-12-63-005
                                  ***