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tile making/ thinset adhesion

updated tue 10 feb 04


terry sullivan on sun 8 feb 04

Ok, enough of this speculation about groves in the backs of the tiles
etc. for bonding with thin set mortars.

It just doesn't matter folks. The bonding strength between modern "thin
set" tile setting mortar and the tile will usually exceed the
structural strength of the tile and certainly exceed the bond between
the thin set and the cement underlayment ( this stuff was not developed
for use with wall board etc. ).

As was previously stated; it is the tooth dimention of the spreading
trowle, which is determined by the thickness of the tile, that provides
the setting for the tile.

How do I know this ? Fifteen years as a licenced tile contractor in
California with up to 30 tile setters working for me. Also; I'm a
graduate of the Ceramic Tile Institute. In those 15 years we set
hundreds of thousands of sq. ft. of every concievable type of tile and
ran hundreds of tests on every setting adhesive and substrate.

Now about those grooves. Recently we have found that deeply grooving
the backs of high relief carved tiles does seem to help prevent drying
cracks in some stoneware bodies.
However; Linda Blossom makes very thick stoneware " tile " mural pieces
with no grooving and the tiles fire just fine. So I think it's the clay
body that is the factor there.

Note that most comercial stoneware tile has a fairly flat back side.
Lots of other tiles have some sort of ridge or grid pattern on the back.
That's because these tiles are usually ram pressed from fairly dry clay
and the pattern is just part of the mold. Those patterns and ridges are
mostly from tradition and don't have a damn thing to do with setting
bond strength unless the setting was done less than optimum in the first

Terry Sullivan
Nottingham Center for the Arts
San Marcos, CA
respond to:
( no response is reply to clayart address )