Sometimes I get asked how to backbutter mosaic tiles. I constantly have to tell people that you really don’t need to. There are very few instances when you’ll need to backbutter a mosaic tile. Normally if you feel the need to backbutter mosaics it is easier to simply use a larger trowel on your substrate.
It is, however, a very handy thing to be able to do when needed. In the case of all these photos I chose to backbutter, or more pointedly put the thinset on the back of the tile rather than the substrate. The width of the niches these mosaics were going into was smaller than the size of my trowel, which makes it difficult to properly comb thinset on the back of the niche.
To backbutter mosaics simply grab a scrap piece of your substrate, in this case it was kerdi-board, and comb the thinset onto it just like you would if you were installing the tile to it.
Once you get it bedded properly, peel the sheet of mosaic off of the scrap piece of substrate. You’ll have a sheet of mosaic with thinset fully covering the back of every tile in the sheet. You can then just install it wherever you need it.
If you are using translucent, or semi-translucent glass mosaics, which is simply big words for stuff you can see through, be sure to flatten the ridges in the thinset first so they are not seen through the mosaic.
This works well in the back of niches, small areas that need mosaic, or anywhere else it’s difficult to stuff a trowel full of thinset into. It also ensures complete coverage if you are doing something like placing mosaic tiles on the ceiling of a shower.
In the few instances you actually need to have thinset on the back of a sheet of mosaics this is a very handy trick to have in your bag.
You can click on any of these photos for a full-size example of my horrible photography skills…