Tile "CRAZING"

[todd....@us.nestle.com]

I recently found some handmade ceramic wall tile I want to install on a
bathroom counter. The owner of the tile shop pointed out that "crazing"
was likely and if we like that look, then we would be fine.

What is crazing? Why does it occur in handmade tile and not mass-produced
tile? Does it happen over time or does it happen right after
installation? Do these cracks/crazing occur in the glaze or the actual
ceramic tile? Is this a purely cosmetic thing, or does this effect the
long-term stability or moisture protection of the tile?

Any help from you tile experts will be appreciated.

Regards,
Todd

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[Ask Mr.Tile]

To Todd
Tile crazing can occur in different ways,the oldest way would be when tile
get old and through time the tiles will craze,the glaze just doesn't have
the strength and durablility that it once had.A good glaze will be fired
at higher temperatures.The hardness of the glaze depends on the
temperature of the kiln and the length of time the tile is in the kiln. It
is important to know the quality of the glaze when purchasing tiles. Soft
glazes are inappropriate for floors and countertop installatioions,where
everday use would chip the glaze .
Unglazed tiles drive their color from the clay. Glazes add color and
protect the surcace of the tile.Many times additivess are mixed with
glazes to produce textured tiles.
Glazes are composed of lead silicates and pigments and area brushed or
sprayed on the surface of the bisque and fired.
A weak glaze in many instances will be fired (in a kiln) in a shorter
duration of time.
Kiln temperatures vary from about 900 degrees to 2,000 F.
Lower firing temperatures produce exceedingly porous tiles and SOFT GLAZES
Kiln time varies from just hours to days.
Nonvitreous tiles are very porous tiles, they absorb more thatn 7
percent of their weight in water. They are fired at a low temperature,
about 2,100 F
close to 20 hours .These tiles becuase they are porous will absorb
moisture and crack.So if it is a very cold area in which you live,and
becuase it is fired at such low temperatures, that glaze more than likely
will crack.
Glazes repel moisture from the tip surface of the ceramnic tiles, but do
not protect the edges and sides. Remember water absorbsion can lead to
cracks in the tile.Because the clay underneath is porous.
I've had jobs,(and this happens in brand new installations,were you get a
tile which has been fired at lower temperature and is clay underneath.The
glaze is very brittle) We just grouted this particluar job and when we
walked away from it,we could actually believe it or not, hear it crack as
we were leaving the job.
Good Luck
any other questions,just:
Ask Mr.Tile
http://www.pyramidtile.com
If you get a chance,check out our site :)

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