In order to replace damaged tiles, it can be helpful to identify
the manufacturer and the approximate date of the tiles, if possible.
However, many mass-produced tiles are not marked and give little
or no information as to their origin, although stylistic similarities
with other marked tiles may sometimes provide a clue as to the
manufacturer. Some decorating firms seldom signed their work,
while many firms made bisque tiles (plain, unglazed, once-fired
tiles) for other companies, as well as their own use. Identifying
marks will generally be found on the back of the tile. A mark
impressed or molded into the back of the tile may give the name
or initials of the company which made the tile or the bisque;
sometimes a printed or painted mark indicates if it was decorated
by a different company, or artist. Historic building records
and construction documents may provide information about the tile
company or supplier. Catalogues of the period may also be useful
in identifying the tile manufacturer of unmarked tiles.
Replacing a single damaged tile is based on the ability to remove
only the deteriorated tile without harming surrounding
tiles. Attempts to remove one or several damaged tiles often
fail because a hammer and chisel are used. The shock of the blows
to the tile being removed travels through the grout into surrounding
tiles and cracks them. To avoid damaging good tiles, all the
grout around the tile must be removed. This is best accomplished
by an experienced tile installer using a hand tool called a grout
saw or, for grout joints wider than 3/8", a dry-cutting diamond
blade, mounted in an angle grinder or circular saw.
Other difficulties may be encountered when selectively replacing
damaged tiles with reproduction tiles. New tiles, especially
encaustic tiles, may be different in thickness and, sometimes,
despite the attention to detail of the reproduction process, slightly
different in color and design from historic tiles. This can cause
both visual and physical problems, especially if the replacements
are being laid in a piecemeal fashion.
If the setting bed does not have enough mortar to grip and hold
the tile, one new tile laid among the originals will eventually
come loose. If the new and old tiles are different thicknesses,
the setting bed in which the new tiles are laid must be at a different
height to create a level finished surface. In addition, the two
levels of setting beds may be of different composition; one may
be harder, stronger and less flexible than the other. This may
also lead to problems, since the setting bed foundation should
act and respond as a unit to the load and stresses placed upon
it.
"Preserving Historic Ceramic Tile Floors" an Historic Preservation Brief
