Unexplained cracking of glass tile mosaics in a swimming pool or spa are more than likely an issue of recycled content or impurities in the glass.
If your glass tile swimming pool or spa experiences random cracking in glass tiles, it is more than likely a manufacturing defect, than an installation error.
But how do you prove this?
Mount the tiles on a sheet of 3/4 inch CDX plywood, following the proper cure times for thinset and grouts. Place the plywood into the same environment as the cracking tiles. Place a duplicate sheet into the direct sunlight. Place a container (tupperware tray) of loose tiles into the same environments.
If the loose and mounted tiles randomly crack, then there is a manufacturing defect. Additional testing will be required to determine the exact cause.
If only the mounted tiles crack, then there is an issue of thermal expansion. The cracking is occurring because the tiles are constrained by neighboring tiles and grouts. Laboratory testing will conclusively vet the cause.
If only clear mounted tiles cracked, then there may be an issue of the thinset heating up in the sun. The clear tiles usually pass more IR light resulting in excessive heating of the substrate. This circumstance will require additional laboratory testing to validate the hypothesis.
If you are thinking about installing glass tile mosaics into your swimming pool.. find out if the thermal shock testing of the tiles was performed in the mounted condition (installed and constrained) or loose.
Loosey goosey is muy malo!
(loose testing is very bad)
Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool and Spa ©www.aquatictechnology.com
You may contact Paolo Benedetti at: firstname.lastname@example.org or at 408-776-8220