QUESTION

Installing Thin Glass Deco Inserts - We’re using GE Silicon to glue a piece of our glass mosaic to a piece of Formica in order to increase the thickness so it can be dropped into a stone border design. Do you see any drawbacks to this? The scored Formica back will be in contact with the thinset, or whatever setting method is used for the stone. The piece of glass will not be more than 2”x2”. Will the silicon yellow in sunlight? Can the silicon withstand freeze-thaw cycles? Any other questions I should be asking the manufacturer?

ANSWER

ANSWER - What you are suggesting doesn’t meet any industry standards, so if something goes wrong you buy it.   In theory the silicone will bond the glass tile to the Formica, but there are some questions.  1.  If the backing to the glass isn’t flat and consistent it may show through the glass.  2.  If too much silicone is applied it may compress with point loads and could cause the glass to crack.  3.  Is maybe the silicone will yellow.  You have to check with the manufacturer.  I would expect silicone to be freeze thaw stable, but you should confirm.  Also check and see if it is being used on an exterior application because you have to make sure it is suitable for that exterior exposure.

You have to make sure that the thin-set adhesive will bond the Formica to the substrate.  Some modified thin-sets will bond to some vinyl but you have to see if it will bond to Formica.  

If you are using the Formica to build it up like only a ¼”, then you can use a medium bed thin-set to do that during the installation.  That is how it is normally done.  If you have to go thicker you can use cement backer board to thin-set to the slab where the hole is left after installing the stone, and then thin-set the glass to it.  Or if you do it like some of the old pros you can make a box-screed.  You key in the thin-set to the glass and then put it into a boxed frame so the top of the box is how thick you want the tile to end up, and then apply mortar on top of that and screed it off flat.  Then thin-set that piece to the substrate.