The ONLY thing that determines the type of grout is the joint size. There are some who weill tell you that you should never under any circumstances use sanded grout with polished marble, and that's all well and good...... so long as you use less than 1/8" joint. I've worked on several commercial crews where we used 3/16" joints, grouted it with sanded grout, and then used an old old method of rubbing dry grout into it with burlap to bring the joints flush and clean the tile. Now if DRY grout won't scratch it,you can bet wet grout won't. (in fact one crew I was with, we did all the Filenes and Lord and Taylors in the northeast, and the gry grout was rubbed in with a buffing machine, and still no scratches, on crema marfil) I'm in Bridgton, Maine, about an hour northwest of Portland, and halfhour east of Conway, New Hampshire. :-)

depends on the tile - if it's really soft stone like Onyx, sanded joint filler will scratch the polish - I had to go and make an inspection on a ceramic tile job where the knuckleheaded installers (they were NOT Pro's in my opinion) scratched the gold leafing on $150.00 A PIECE ceramic tile liners when they used SANDED JOINT FILLER... it scratched the Gold leaf right off the tile and they ate an $18,000 dollar tile order that had to be replaced at their expense. That was NOT a happy day at their office!!!! Joints that are 1/16" or tighter in most cases will be fine with dry grout (non-sanded). As the joint width gets wider, the dry grout (non-sanded) will shrink too much and develope tiny hairline cracks in the joints... not cool. sanded joint filler is used in joints 1/8" and wider - the sand helps eliminate the cracking, plus it's a slightly different type of blend of cements and dyes to help eliminate the hairl;ine cracks too... what is the natural stone you are grouting? this will have some bearing on which type of joint filler I would suggest you use...... kevin Kevin M. Padden MIA SFA Fabricator, Trainer & Consultant to the Natural Stone Industry www.azschoolofrock.com

When we mixed the grout (unsanded)for our backsplash, it was very stiff, making it a pain (more work) to press into the 1/16" joints with the float. We really had to work to get it applied. I don't know if it's possible, but maybe they mixed in a little more water to make it easier to apply on the sample boards. When we made our sample boards, we mixed up small amounts of the grout by hand to use, as we were just wanted to check the color. We mixed the grout used on the actual installation with the drill and an attachment for mixing concrete type materials. You might show them the sample boards and ask why it's crumbly.

but I do know that sanded is much stronger and hold up better. I think it is intended for 1/8" or wider grout lines. It's not that it's stronger. It's that it doesn't shrink as much, because of the fact that most of its bulk is the sand. As for the explanation of the different grouts, I just posted this in an FAQ thread on the gallery side of the bathrooms forum. Here it is, copied and pasted: Although there are others, for all intents and purposes, there are two kinds of grout-- portland cement based, and epoxy. The portland cement based grouts are the conventional grouts that have been around for millenniums. Although in the last few decades, they've been modified with latex and other polymers to make them stronger and more resistant to mold and mildew, they're basically the very same grouts that have been used since Greek and Roman days. There are two kinds of portland cement based grouts. One is sanded, and the other unsanded. The only difference between the two is, as their names imply, the sand. The ONLY thing that determines which grout should be used is the joint size. NOT the glaze, NOT aesthetics, NOT the material (ceramic vs. glass or polished marble), NONE of those. I'll repeat-- the ONLY thing that determines which is used, is the joint size. Anything under an 1/8" takes unsanded grout. Anything 1/8" or bigger, you use sanded grout. If you use unsanded grout in larger joints, the cement in the grout will shrink way too much as the water evaporates out of it, and the joints will end up shrinking and cracking bigtime. If you try using sanded grout in smaller joints, the grains of sand will literally clog the top of the joint, and not allow the grout to get down INTO the joint, and the grout will flake off in a matter of days. As for the Epoxy, most epoxy grouts use a much finer "sand", and therefore can be used in any size grout joint. Further, epoxy grouts are everything people say they are. They're much easier to clean, practically stainproof, and also extremely expensive. Most epoxies will cost atleast 4 times the cost of conventional grouts, and the installer will also usually charge a premium of between 1.50- 2.50 a foot for the use of epoxy grout. There are alot of people who will disagree with me, but my own opinion is that for most residential installations, epoxy grout is bigtime overkill. The ONLY times I'll recommend epoxy grout is first, if you're installing a tile countertop, and two, if you have animals in the house that either aren't housebroken, or are prone to accidents. In either of those cases, epoxy might be worth the money. For anything else, though, conventional grout is more than good enough.