Best way to grout mosaic tile with open-hole porous tiles


Old 02-26-14, 09:54 PM
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Best way to grout mosaic tile with open-hole porous tiles

Am installing a mosaic tile backsplash with a mix of glass and stone. Some of the stone is white(ish) stone with open pours. I am grouting using an antique white.

I pre-sealed all the stone tiles with 511 Impregnator and waited multiple days for cure. The first section I grouted using the traditional float method. While it is not fully dry and haven't wiped the haze off yet, it appears that the white stones were still stained and some of the holes filled. While I'm hopeful this will flake away as it dries, Murphy says otherwise.

- What should I have done differently? Am considering masking each stone (painful) or using a grout back (only slightly less painful).

- What can be done if anything to help the stained tiles. I'm headed down the toothbrush and acid route.
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Old 02-27-14, 05:39 AM
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You might need to apply another coat of sealer if the stone is so porous that it's still absorbing or being stained by grout. As for pits in the stone there is not much you can do other than mask them off or use a grout bag since it's a simple problem of grout getting into a recess.

I also use a very firm sponge, lightly dampened to buff and remove as much of the grout off the surface immediately. Not following the old recommendation to allow it to harden before removing the final haze. The key is to use a firm, flat sponge with light pressure that will not get down into the joint and remove the still soft grout but stays on the surface cleaning it before the grout can harden or stain.

Muriatic/hydrochloric acid can be used to clean cement based grouts though care must be taken as it can also attack some stones. A diluted solution dampening a firm sponge lightly rubbed over the surface may remove some residue and color but won't do much to get into pits of stone. And unfortunately many stones used in tile that have pits are readily attacked by acids.

I hate to say it but I very carefully examine any material before choosing it. There are some incredible tiles available these days but some are almost impossible to grout. For a guest bath back splash that gets little use I might pick some tiles knowing the area is small so the extreme labor to grout is not such a big deal or go without grout altogether. For a working kitchen back splash or master shower I give a lot of attention to how it will be grouted before choosing that material.
Old 02-27-14, 09:13 AM
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I think I know the tile you're using, it's very common these days.

But, I believe you're trying to do this wrong. You are supposed to fill those holes and cracks. You don't want holes for all kinds of matter to get in.

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