A:Michael Byrne, a veteran tile installer and consultant, and the moderator of JLC’s ceramic tile forum, responds:
For any type of tile, you need to use proper grouting techniques if you want an attractive finish, but textured surfaces require extra care and more time. “Textured” can mean anything from small bumps on ceramic tiles to the craggy ridges of hand-split paving stones. For most ceramic tiles with a textured glazed surface, normal grouting techniques work just fine, whereas on particularly rough surfaces, I may apply the grout with a grout bag. Slate tiles usually fall somewhere between the two extremes.
One trick is to keep the grout and haze from drying on the tile surface. Grout-release liquids or sealers may be applied to the tile as a barrier, but these products may have to be removed after grouting, which creates its own set of problems. Also, releases and sealers must be allowed to dry before grout is applied, slowing down the installation.
Instead, I prepare all but the slickest tile surfaces in a way that is simple and inexpensive—and especially helpful when the surface is textured. All you need is a bucket of clean water and a sponge. Simply wet down the tile surface with a damp sponge immediately before grouting, and keep the water and sponge close by to keep the surface damp as you grout. This “wash” fills in the tiny nooks and crannies in the textured surface, so the grout doesn’t stick. It’s important, however, not to get the tile so wet that puddles form on the tile or in the grout joint (excess water can significantly reduce the cohesive and compressive strength of the finished grout). Note also that some textured tiles are very absorbent and may need to be washed several times to keep the surface damp.
Depending on the air temperature and humidity, as well as the coarseness of the tile surface, I may grout and clean only 10 square feet or work the entire surface. (Cooler temperatures and higher humidity mean I can work a larger area before the grout starts to set up). If the grout is soft and has yet to set up after packing 10 square feet or so, I’ll grout another 10 square feet and check the starting point again. If it has still not begun to set up, I keep installing more grout—about 10 square feet at a time—until the grout at the starting point has begun to set up. As each 10-square-foot section is grouted, I scrape off any excess grout with a trowel, holding its face 90 degrees to the floor and on a diagonal to the joints (photo, BB PLS LOCATE). This makes cleanup easier and faster.
Once all the joints in the area I’m working on are grouted and the excess grout removed, the next step is damp-cleaning. Start by lightly scrubbing about 10 square feet of the surface with a moderately damp—not wet—sponge in a circular motion to loosen the grout that is beginning to set up. Rinse the sponge, wring it out thoroughly, and then lightly scrub the surface again. Repeat until all visible traces of grout are removed. When the entire installation has been damp-cleaned, the surface may appear to be clean, but it’s actually covered with fine cement particles, which cause the haze that can be so difficult to remove from a textured surface.
For the final cleaning step, rinse the sponge and wring out as much water as possible, then re-rinse the sponge in a bucket of fresh, clean water. Again working in the same small area, slowly wipe the surface of each tile, moving the sponge parallel to the grout joints (see photo, BB PLS LOCATE). After one pass, turn the sponge over and make a second pass that slightly overlaps the previous stroke. Then rinse the sponge and repeat until the area is clean before moving on. Never use the same side of the sponge for more than one pass, to prevent redepositing grout material onto the tile.
If some haze remains once the tile surface is dry, you may need to lightly re-clean the floor with the sponge, repeating the one-pass-per-side step. If after that small patches of light haze still linger when the tile dries, a light rubbing with a soft, clean cloth or towel should remove them.
Crucial to the success of any tile job is staying at the installation until the surface dries and re-cleaning the surface as necessary to remove any lingering haze. If you wait until the next day, the haze will have had time to partially cure, which will make final cleaning difficult, tiring, and time-consuming. If buffing with a soft cloth or towel does not remove all the haze, scrub the affected areas with a fine-grain plastic abrasive pad and a little water. Then clean again with the one-pass method described above. Persistent haze may require a grout cleaner, but first make sure the cleaner won’t harm the tile. Spot cleaning may change the appearance of the tiles, so after checking the cleaner’s effectiveness on a small area, use it on the entire floor.
The last-ditch strategy for removing haze is acid cleaning, which is hazardous work that requires careful preparation, use of safety equipment, careful application, thorough rinsing, and proper disposal of the rinse water. But be aware that cleaning with acid may not be appropriate for some stone tiles.
Once the floor is clean and dry—and before it is opened for foot traffic—seal the grout and tile surfaces with a sealer made specifically for use with stone and approved by the grout manufacturer.