Is the glass frosted? that is the only thing i can thing of...grout can sometimes be a bear to remove from frosted glass. p

I just completed a whopping pile of glass mosaic stepping stones and used a penetrating grout sealer. A thin film of sealer was left on the glass. I left it alone, allowed the sealer to dry & set for 24 hours, then came back over the glass with a damp wash cloth (a cheap, nubby one) and the residue wiped right off. I couldn't see where it disturbed the sealant on the grout at all and it was easy peasy :-)

I imagine the glass tile is either pitted or frosted and the sealer is to prevent the grout from staining or remaining in the pits of the tile.

Just a guess.

How about Weldbond on top of the tiles? It can be easily wiped away afterwards.

Have you asked this question over in the Garden Web Bathrooms Forum? The tile folks there are generous with their information.

Good luck.

Here is a link that might be useful: Bathrooms Forum

Thank you for the replies, They were much appreciated. maddielee, yes, I've been on the bathroom forum...since Feb when we started discussing our master bath remodel. The expert tile guy there told me to NOT seal it :o
mosaicwench1, yes, you were right. These tiles are crushed glass on the inside and the surface has very fine "fissures" that if not sealed the grout will stain them. I was having a heck of a time speaking to someone at the manufacturer's that could make me believe and understand why I needed to seal the tiles and the worry I had about the sealer causing the rest of the tile to be hazy. Well the haze issue turned out to be a NON-issue and it was a DARN good thing we sealed them before grouting. (I think) there was one small (3") area in a corner I missed sealing. We can see some grout staining. It's minimal and will more than likely become even more so as the grout dries. No one will notice except me :) That's the only place we can see any staining so that's why I think I must have forgotten that area. Thank you all again for your input :)
Monica (who will now slink back to the kit/bath forums) :)

You cannot "seal" glass tile. It is impervious... after all rainwater does not come through your windows or your windshield, does it??

This is why it is chosen for cookware (Pyrex)... it DOES NOT ABSORB ANYTHING (virtually nothing) !

As for the internal fissures, cracking, fractures, spalling, & failure of the glass mosaic tiles - refer to this site for the information you are looking for. It is an internal flaw within the tile : http://watershapes.blogspot.com/2009/06/failure-of-glass-mosaic-tile-fracturing.html

Here is a link that might be useful: Glass mosaic tile failures

great i saw this one. i am not experienced so i have questions.
my first piece of mosaics ever is this mirror
http://home-and-garden.webshots.com/photo/2792710730104010362ToOvoj
especially on the light blue tiles, i can see some very small dots of grout
http://home-and-garden.webshots.com/photo/2598026200104010362RzHcFM
the piece was made using vitreous glass tiles
http://www.thecraftkit.com/index.php?main_page=index&cPath=47_5
these tiles are not perfect, they do have fine small hollows that got filled with grout.
was there something i should have done before grouting?
those dots are very fine and can't be seen from distance. they don't bother me... but in the future, if there is something i should be doing before grouting, please let me know... sealing?
all the sealing products and brands you might mention are not too useful, as over here in romania we probably have other names for them. would be impossible to identify the product.
i am also making my second one using Murano Smalto which is same material as smalti but more regular in shape... but still not perfectly smooth - still has cracks and small hollows...
http://www.thecraftkit.com/index.php?main_page=index&cPath=49_17
don't wanna end up with more grout on the pieces...
any advice???
THANKS,
CALIN