Swimming Pool Glass Tile Mosaic Cracking - Tile Edge Quality

Poor Edge Tolerances

There are many reasons why glass tiles crack.  The most common is damage to the tile - a chip, scratch or impact.  These traumatic events occur during the manufacturing, handling, shipping or installation process.

Manufacturing Processes

Glass tiles are made into small squares by a number of various processes.  Cast or pressed, individually cut or snapped are the three most widely used methods.

Cast Tiles
Cast tiles are created when molten glass is poured into molds, individually forming each tile.  The process may be inverted, when a cookie cutter style press stamps out individual and distinct tiles.

Cut Tiles
Cut tiles are formed by cutting the tiles from a larger sheet of glass.  The tiles are usually then re-fired in a kiln to relieve stresses imparted during the cutting process.

Snapped Tiles
Snapped tiles are a more rudimentary method of forming tiles.  These are made by one of two processes: 

• a cookie cutter style mold presses the tile shapes into molten glass.  The cutter does not separate the tiles into individual pieces, leaving them connected by a thin layer of glass.
• molten glass is placed onto a mold tray and allowed to cover the mold.  It is then pressed or allowed to fill the cavities.  The tiles are connected by the layer of glass that remained across the dividers.

After annealing, they are later "snapped" apart, creating the separate pieces.  The process of snapping imparts chips and stress along the edges of the tiles.  Unless the tiles are re-fired in the kiln, these stressed tiles are handed off to the consumer.

Hard to Detect

These chips and stresses are hard to detect.  Since the tiles are usually mounted on an opaque paper, inspections are difficult for the end user, if not impossible.

Resulting Cracks

The stress that concentrates around these imperfections from thermal expansion will cause the tiles to crack.  Because not every tile has these imperceivable flaws, the cracking will occur randomly and the manufacturer will blame the installation practices.


Paolo Benedetti - Aquatic Artist "Creating water as art."™ 
Aquatic Technology Pool and Spa ©www.aquatictechnology.com 
You may contact Paolo Benedetti at: info@aquatictechnology.com or at 408-776-8220