For this process you will need to use an epoxy grout. I prefer a product called SpectraLOCK® Stain Proof Grout. It is a three-part grout that is mixed right before using. You’ll want to use rubber gloves during this process, epoxy grout sticks to everything it touches and is not removed easily.
First, smear the grout around on the panel making sure you get it in every crack between the glass pieces. This will not only strengthen the entire piece but because it is an epoxy grout, it will seal the piece. It’s important to use only one package of grout at a time, this process is time-sensitive and you don’t want your grout to dry before you’re ready to start the next section of your panel.
After you worked the grout in, use a damp (not wet) sponge and start cleaning the surface off. Clean it as much as you can, let it sit a couple of minutes, then buff it off. Repeat the process untill the panel is completely grouted.
Finally, perform a final buffing of the panel and prepare it for framing.