Terracotta tile floor

Davide Fodaro <dfodaro [at] tiscali__it> writes

>I am an Italian conservator specialized in ceramic and glass
>conservation. Now I am starting a conservation project of an ancient
>cotto floor (in Italy, "cotto floor" is a floor made of terracotta
>tiles, not glazed).
>
>This is the floor of the Galleria Spada in Palazzo Capodiferro in
>Rome. The age of the cotto floor is the 17th century. It is covered
>from a thick and oxidized wax layer. I think that laser cleaning
>could be used. What do you think? Have you carried out similar
>cleaning?

I am more familiar with 19th century and later terra cotta, but I
would imagine that 17th century terra cotta manufacture would have
been similar. Most unglazed terra cotta has a fire skin of colloidal
silica that has undergone partial vitrification. The fire skin
increases the durability of the material through reduced porosity.
Abrasion cleaning methods are usually not recommended for fired clay
products because the fire skin (which can be very thin) is often
removed.

I would imagine that laser cleaning would have the potential to
remove the fire skin if it is not very carefully controlled. Here in
the U.S., non-ionic detergents are frequently used for cleaning
architectural terra cotta (glazed and non-glazed). Although it may
take many passes to clean oxidized wax from a floor, the technique
is gentle and should leave the original tile intact.

Jeremy


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                  Conservation DistList Instance 16:63
                 Distributed: Wednesday, April 23, 2003
                       Message Id: cdl-16-63-005
                                  ***