I have Spectralock Silver Shadow (a light gray) with my honed carrara basketweave tile. I tested the grout before install with both sealed and unsealed versions of the marble tile. I did not notice a difference with either version as far as a picture frame effect. The marble did darken slightly but this was an overall effect and only very slightly (DH didn't notice at all) and it was uniform on both versions (this may be due to setting in white thinset). It has been at least 4 months and I haven't noticed any change from the initial install.

Spectralock is great grout. I use it in shower floors alla time. On a backsplash, I think of it as "overkill." What are you trying to do? Walk on it? A quality, sanded grout if just fine.

I agree with Laz.

Thanks for the info socalsister! It came down to the Platinum or the silver shadow, but I want to go with the platinum to tie in more with the rest of the kitchen. I would be ok if it darkened a little overall- just as long as it doesn't create a frame around each tile.

lazarususa and bill- I know normally it would be overkill, but I read all over the place not to use sanded grout with marble and that sanded grout can't get into tiny (1/16" spaces), which I have. The unsanded grout won't work on the 1/4" spaces. So as far as I know, that leaves me with epoxy. It was only $25 for a kit. Even if I end up needing 2 of them I don't think that's too expensive. This is my first tile project, so please let me know if I've misunderstood.
Thx.

Quite frankly, I don't care WHAT they say about marble and sanded grout. I'll go back to my usual mantra-- there is only ONE factor that determines whether you use sanded or unsanded grout, and that's the size of the grout joint.

That said, I've heard the whole thing about scratching polished stone by using sanded grout. I've done aisles at Lord and Taylor using crema marfil-- one of the softer stones around-- and we always used a 3/16" grout joint, which means without a doubt, sanded grout. When we'd clean it up, insted of using sponges, we'd use an old fashioned method of dry (sanded) grout and burlap, rubbed into the face of the stone, which completely fills the joints, and cleans excess grout off the face. it gets better. not only did with rub the sanded grout into the face of this stone with an abraisive cloth, but we used a BUFFING MACHINE to do it!! The heck with that scratching stuff. Someone would have to be TRYING to scratch the face of marble, as far as I'm concerned.

One other thing to think about is using Laticrete's Permacolor grout. The sand in it's alot finer than most grouts-- to the point that you can use it in ANY size grout joint. I know I've personally used it with polished carrara marble, and didn't have a single problem. Pics below.

Bill,
Thanks again for sharing your expertise! I will happily go with the Laticrete Permacolor in that case.

A few more questions:
1. Have you used a darker color Permacolor grout with a white marble and had the color be absorbed into the stone?

2. The sanded (vs unsanded) premium acrylic caulk will match?

3. Should I use the caulk on the inside wall corner or just where the tile meets the counter?

4. I have 15 sqaure feet of 2x2" tile: how much grout and caulk will I need?

Thanks again!!!

5. Does the Permacolor grout need to be sealed if used in a backsplash?

1. Have you used a darker color Permacolor grout with a white marble and had the color be absorbed into the stone?

I've yet to hear from ANYONE of staining problems using Permacolor.

2. The sanded (vs unsanded) premium acrylic caulk will match?

Either one. Personally, unless it's a smaller grout joint, I'd prefer the sanded.

3. Should I use the caulk on the inside wall corner or just where the tile meets the counter?

I'd use it in all places where one plane meets another. (fancy answer for both! :-) )

4. I have 15 sqaure feet of 2x2" tile: how much grout and caulk will I need?

10 pounds would work, but I've yet to see Permacolor in anything smaller than 25 pound bags. Only thing I've seen (in 10 pound containers) is the 1500 and 1600 (sanded and unsanded) standard grouts.

5. Does the Permacolor grout need to be sealed if used in a backsplash?

Not so far as I'm concerned.

please note that two of the three people posting above have written, or agreed, that for a wall, epoxy grout might be overkill. I also agree. The 3rd person did not state whether their experience was for a wall or a floor.

To that I'll add that the wide spaces might allow epoxy grout to slump, so you might have to sit up with it overnight to keep pushing it back into shape. Sometimes hardening is a slow process. Sometimes it is fast. In both situations you have time to push the surface down a bit (it's not like reworking the surface). In a worst case view, the grout would slump and not just in the widest spaces. Too many factors to know in advance.

Several times, I've used epoxy grout on shower walls. No slump. Don't worry. Good to know about this if it happens.

your previous thread:

Here is a link that might be useful: Laticrete SpectraLock Pro grout with Calacatta marble?

Bill: THANK YOU THANK YOU THANK YOU for your quick answers. I'll definitely go with the Permacolor.

davidrol, thanks for the additional input on epoxy being overkill in this application. : )