How to Make Glass on Glass Mosaics

Surfaces

Only limited by your imagination but can include vases, bottles and jars. I've used a glass brick which I picked up at Bunning's for about $10, which could look great as a feature in your home. If you are using a glass vase etc you need to take into consideration that you may see the back of your mosaic through the opposing sides.

Adhesives

Clear drying glue such as Weldbond. Make sure the glue will adhere to glass.
Weldbond Glue - When bonding glass tiles to a glass surface, use Weldbond sparingly if you require a crystal-clear bond. Any whiteness indicates the curing process is not complete.
Clear Silicone - Use plenty of clear silicone, pressing down to ensure there are no air bubbles. Note: I found that my silcione dried with clear adhesive lines, not a crystal clear finish.

Preparation

The glass must be completely clean prior to applying any adhesives. Rub the surface down with methylated spirits prior to applying glue.

Tips

• Any whiteness in the adhesive indicates that the curing process is not complete. Do not start grouting until the adhesive is completely clear.
• If you are intending on grouting you need to make sure that there are no gaps where glue can seep under the tesserae. 
• It is a balancing act between getting a crystal clear finish and making sure you have enough adhesive applied so that the grout does not seep underneath.
• I found that it is much easier to achieve a good result with smaller tesserae (e.g. gems, pebbles, tiles) than larger tesserae like the irregular glass gems, simply because of the surface area that's being adhered to the glass.
• A good result takes time; don't rush the laying of the tesserae.

This is an example of the adhesive under the green gem glass gem not being cured, Weldbond glue appears white until fully cured.

This is an example for grout under the tesserae, the yellow gem appears brown in spots.

The smaller tesserae worked well in the mosaic.