Cleaning ceramic floor tiles

In Cons DistList Instance 12:58 John Desmarais asks for advice on
cleaning ceramic floor tiles which are heavily encrusted with dirt
and which may or may not be glazed.

First of all, avoid caustic soda (sodium hydroxide) or muriatic acid
(hydrochloric acid).  Both of these are dangerous if used carelessly
and could harm the tiles too.

In order to decide on the best method of cleaning the tiles, you
need to decide what kind of dirt you have, and whether the tiles are
glazed or not.  If the dirt is ordinary household grime it will be
easier to remove than, for example, greasy kitchen dirt.  Try
carefully scraping away some of the dirt to reveal the surface: even
if the tiles were originally glazed it may be worn away completely
or partially in the most heavily trafficked areas, so try round the
edge of the room.  If there is glaze, is it firmly attached, or is
it tending to craze and flake?

Depending on the presence and state of the glaze, it may be safe to
use a domestic floor cleaner, taking care to rinse it well.  If
there is stubborn grease or wax, it may be necessary to use solvent
cleaning, but again there are safety considerations.  Last year we
successfully used a methylene dichloride paint stripper to remove an
accumulation of wax from medieval floor tiles at Westminster Abbey,
but before doing this we had to carry out a health and safety
assessment and ensure there was adequate ventilation.

In summary, then, go carefully; try to find out what condition the
tiles and any glaze are in before applying anything to the surface.

Barry Knight
English Heritage
London

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                  Conservation DistList Instance 12:59
                Distributed: Wednesday, January 20, 1999
                       Message Id: cdl-12-59-002
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