When working with glass tiles and mosaics it's important to use a Mortar that has been formulated to work with glass tiles and mosaics. We recommend using Mapei Adesilex P10. This is a white premium grade modified thin-set with non-sag properties designed for use with glass tiles and mosaics. It also has polymer added to it which improves bond strength and flexibility in the mortar. As temperatures change through out the seasons your house will under go some expansion and contraction. Having some flexibility in the mortar will help alleviate risk of cracking in your tile which could happen if an unsuitable mortar was used during installation.
Two things we like about this mortar....
When tiling vertically in a kitchen backsplash or tub surround you're going to be working against gravity! A non-sag mortar will help with this as it tends to keep the mesh from buckling under the laws of gravity. This help work towards nice even grout lines for a professional finish.
2) White Coloring
Although the majority of glass tiles are back painted and 99% nontransparent, we think using a white mortar is a good idea as it wont effect the color of the tile as light bounces off of it.
Mapei P10 is carried by several building supply stores through out North America.
We suggest using Mapei Keracolor U non-sanded grout. It's important to use a nonsanded grout with glass tiles, as sanded grouts can potentially scratch the glass surface. This grout should only be used with grout lines between 1/16" - 1/8" (1.5 mm - 3 mm). If you are considering larger than 1/8" grout lines with your subway tiles consider using a sanded grout. However, we must caution you do run the risk of scratching the glass. We recommend playing it safe and avoiding the larger grout lines.
Here is a link to the Mapei Keracolor U color chart for a list of available colors.
Mapei products are widely available throughout the United States and Canada. Check your local building store or tile store for availability in your region.