In my previous post, I wrote about how to remove and replace glass mosaic tile to make changes to a mosaic before you grouted it. I also explained why it was good to display the mosaic for a few weeks before grouting so that you had a chance to see the mosaic as a whole with a fresh eye before setting it in concrete.
But writing this got me to thinking about a common problem that isn’t visible until you grout the mosaic, and that got me to thinking about all the ways in which people “ruin” their mosaic in the grouting process. Fortunately, the mosaics aren’t actually ruined, and there are solutions to each problem, at least in the vast majority of cases.
Conventional Grout, Not Epoxy Grout
Keep in mind that all of the mosaic advice on my websites is written for conventional portland-cement grout. If you are using one of the new epoxy-based grouts, then some of what I am recommending might not be possible or might require more work.
Ways Mosaics Are “Ruined” By Grouting
Here are problems commonly reported after grouting a mosaic:
- My mosaic is covered with a dull gray or white haze.
- I let the grout harden on top of my mosaic before I could get it off.
- There are specks of grout in the pits and voids of my glass tile.
- My grout is crumbling and falling out.
- The grout stained my unsealed stone or ceramic tile.
- My grout is not as dark and colorful as it was when it was wet.
- I used the wrong color grout.
- My tiles seem smaller after grouting, or my mosaic isn’t as colorful as it was.
NONE of the above problems mean the mosaic is ruined permanently, and most are relatively simple to fix.
A Dull Gray Or White Haze
Grouting involves pressing wet grout onto the surface of the mosaic, working it into the gaps
thoroughly, and then scraping off all the excess. But that is just the initial phase of the grouting process. The second phase involves cleaning and hazing, both of which must be done with care not to erode the grout from the gaps or moistening it with excess water.
If your sponge or rag contains too much water, then you wipe off the top layer of colored grout in the gaps leaving only the sand, and then the grout will look lighter than intended when it is dry. That is why installers only clean the tile so much when the grout is still wet and curing. They err on the side of caution and leave a thin residue that dries into a haze. That is why the process of buffing a freshly grouted mosaic with a clean rag is called “hazing.”
If you leave a little too much residue, the haze might be more substantial and not wipe off with a rag. If so, no worries. Simply use a Scotchbrite pad or wire brush to scuff away the haze. Do this process wet using a spray bottle to mist the mosaic to avoid breathing dust.
The Grout Hardened Before I Could Scrape It Off
This problem can be thought of as an extreme case of the problem discussed above. If you have excess grout hardened on your mosaic, it can be removed. Concrete can be eroded relatively easy if the total surface area isn’t excessively large. For this situation, we has a wire brush of the type used to clean welds, which has thicker and stiffer bristles than the wire brushes used for cleaning barbeque grills. We mist with spray bottles, and once the excess is worked off, we finish up with Scotchbrite pads and rags as described above.
Specks of Grout In Pits
Sometimes stained glass and even molded glass tile will have pits in the surface that were bubbles when the glass was molten. Naturally grout fills these voids just as it does the grout gaps, and it doesn’t wipe off. Often times, people won’t notice the problem until the grout is cured and lighter. This is a trivial problem. Mist the mosaic with water and use a dental pick to clean out the voids. You can also use a light gauge wire brush if the problem is fairly widespread, but take care not to erode grout from the gaps.
Concrete hardens by binding water, not by drying out. If you doubt this, then think about how concrete can harden underwater. If you let your grout dry out when it is curing, it will be soft and crumbly. Cover your mosaic with a plastic trash bag if the AC or heat or sun is making the air dry. The grout will also be soft and crumbly if you don’t add enough water when you mix it up. Follow manufacturer instructions on the package.
If you have crumbly grout, then scrape it out with the grout removal tool we sell or an old screwdriver and regrout the mosaic.
The Grout Stained My Tumbled Stone or Unglazed Ceramic Tile
Porous materials like tumbled unpolished stone and unglazed ceramic tile can be stained by grout. We prevent this problem by wiping the mosaic with a rag dampened with Tile and Grout Sealer, such as TileLab brand a day BEFORE we grout. We are careful not to get any sealer in the gaps where the grout will need to bond to the sides of the tile, and we have used small artists paint brushes for this purpose.
If you didn’t know to do this, all is not lost. You can sand off the stained layer with 80 grit sandpaper followed by 120 grit and finer grits if needed. Of course, you don’t use sandpaper. Like any craftsperson in the know, you buy the belts used for belt sanders and cut them up. The belts don’t cost much more than sandpaper, but they last literally a hundred times longer.
Also, you should wet sand this using a spray bottle to mist and wear a dust mask to avoid breathing the silica dust.
The Grout Is Lighter Than It Was When Wet
Grout will always be lighter when it is cured and dry, no matter how dark it was when wet, and this is particularly true for dark colors like charcoal black.
There are two solutions:
The first option is to seal the grout with a sealer known as a “stone enhancer” instead of a regular tile and grout sealer. However, enhancers are invisible pore sealers just like regular grout sealers and not a coating that actually forms a gloss layer over the top of the grout. That means there are limits to how much color you can bring out with an enhancer.
If you need an extra dark grout gap, then consider painting it with artist’s acrylic paint instead of sealing it. Glass tile is non-porous, so the paint should wipe right off the glass and stick only in the porous grout. Of course, you should only do this for dry indoor mosaics. I don’t want to get any emails from dodo birds painting the insides of their tile showers.
The Wrong Color Grout
Grout can really change the look of the mosaic, especially if you use wide grout gaps. Grout works best when it serves to separate the tiles visually like a thin pencil line in a watercolor painting. That is why the best choice of grout color is usually a medium gray, unless you are using gray tile. It’s important that the grout color CONTRAST tile color instead of matching tile color. If it matches the tile color, then the tiles will run together visually and not stand out as individual tiles, and the mosaic usually looks poorly as a result.
There are two alternatives when you use the wrong color to grout your mosaic: Scraping the grout out with a grout removal tool or painting the grout with color as described above.
My Tiles Seem Smaller or My Mosaic Isn’t As Colorful
The grout gap always looks wider once it has grout in it. It also has no color until you fill it up with concrete. In an ungrouted mosaic, the colorful sides of the tiles are visible. That means a mosaic with wide grout gaps is particularly susceptible to looking duller when grouted.
Smaller Grout Gaps For Smaller Tile
If you use small tile or small pieces of tile, then remember to use a correspondingly smaller grout gap. Sure, a 1/16 inch gap is standard, but if your tile is 3/8 inch, you probably want to use a smaller grout gap if you are rendering the details of an image instead of merely tiling a wall.
Another solution is to not fill the grout gap all the way to the top. This is particularly important when using tile with rounded corners or a rounded top surface. Think of it this way: If you let only the peaks of the tile show above the grout, then your mosaic’s surface area will be mostly dull concrete instead of colorful glass.
If you haven’t yet grouted a mosaic with wide grout gaps, consider reworking the areas with the widest gaps. Often that isn’t practical because the problem is widespread, so the remaining option is to rub the wet grout off more aggressively than normal when you scrape away the excess and try to erode some of the grout from the tops of the gaps.
If you have already grouted the mosaic, then consider using the grout removal tool to scrape some of the grout from the tops of the gaps. This is particularly effective when the tile used has rounded tops. If you get some of the grout off the slopes of the tile so that more of the faces are showing, then the mosaic can become a lot more colorful. Again, this isn’t as useful an option if the mosaic is wet or outdoors. In those cases, you would have to pay close attention and make sure that enough grout remained to keep the out moisture, and you would need to reseal the mosaic.
Don’t Give Up Hope
It is an act of faith to dump wet concrete on top of a detailed picture that you just spent weeks making by hand from tiny pieces of glass. Not surprisingly, most novices expect the worst when anything goes wrong or appears to go wrong, and they are usually convinced their mosaic is ruined. This simply isn’t true.