The primary reason for grouting tiled surfaces is to prevent water from penetrating behind the tile and weakening the adhesive or the backer and the structure beneath the backer. In mosaic artwork, the grout also has a visual function, and that is to contrast (not match) the tile colors. If the grout color does not sufficiently contrast the tile colors, than all the tiles blend together visually, and much of the “mosaic effect” is lost.Grout Color Should Contrast Not Match
There are some novices who doubt my advice about contrasting grout color and even try to match their grout color to the tile colors. These are the people who later email me in a complete panic. They usually use the words “completely ruined” to describe what grouting did to their once beautiful mosaic, and from the pictures they send, I’m inclined to agree with them. (Note that these mosaics can be saved, but it requires either scraping the grout out with a grout removal tool or painting the grout with acrylic paint or some other ad hoc solution.)A Medium Gray Grout
Since experience has shown time and again that the best grout color is one that contrasts tile color, the question becomes which grout color best contrasts ALL the different colors used in the mosaic. For MOST combinations of tile colors, the best contrast is usually provided by a medium to dark gray, with darker being the better guess if in doubt. Always keep in mind that the color of the grout will be significantly lighter when fully cured compared to how it looks when wet.A Notable Exception: Lighter Blues
There are a few notable exceptions to the rule of gray grout being best. The most obvious exception is when you are using gray tile (duh), but the one that usually catches people by surprise is when tiles of lighter blue colors are used. Unfortunately, these are just the shades of blue that are popular for water and sky elements, so this is a significant exception. In this situation, a warm light brown or sand colored grout might be a good choice for contrasting the blue tile, but what if there are light brown tile used elsewhere in the mosaic? Is there a good standby color of grout for this situation? The answer is no, but there is a quick solution.Go Look At Grout Colors With Your Tile
Building material stores such as Home Depot and Lowes usually carry about 30 or more colors of grout, and they have color swatches on the shelves and/or packaging so that you can pick out grout similar to how you pick out paint, only with much more limited options. The trick or tip is to not to try to do this from memory without the benefit of having your tile with you. Take one or two tile of each color used in the mosaic with you to the store and hold them up against the color swatches. I have even gone into the store with small mosaics, just as I have taken in parts of plumbing I was trying to match or replace. Don’t be self conscious about it. The people who work there are accustomed to seeing professionals at work, and you will be quite unobtrusive compared to the building contractors dealing with emergencies. At least you won’t be covered in dirt and holding a toilet seat or something like that.Some “Advanced” Tips
From the many emails and pictures I have received in the past 12+ years, I can state with some confidence that novices tend to regret choosing grout colors as an attempt to add another color to the mosaic. Matching grout color to tile color tends to be even more disastrous.
If you already have your figures rendered in tile using a relatively small grout gap, and you like how those figures look, then your main objective while grouting should be to not mess up the visual art that was already working, especially if you are a novice at mosaic.
Of course, even a novice can take a few of each color tile and create an abstract experiment on a scrap piece of plywood and try a novel grout color on it.
The monochromatic nature of medium gray grout makes it contrast colors intrinsically, in the same way that back and white contrast colors intrinsically. All three are balanced in hue. The keep-it-simple and less-is-more principles really come into play when you decide to second guess some shade of medium to dark gray when grouting figurative mosaic artwork.
On the other hand, there are all those earth tones to play with…
Just remember to experiment on a piece of scrap before trying it out on a mosaic where 90% of the work was spent cutting and mounting the tile.
This article is about coloring grout for mosaic art before the grout is applied.
This article isn’t about staining grout for bathroom backsplashes. From what I’ve read, staining bathroom grout doesn’t tend to last but has to be refreshed within a year or two. If I wanted to change gout color, I would remove the existing grout with a grout removal tool and then re-grout.
Another problem with grout stains and concrete dyes is that they tend to be limited in color, especially what is available at your local building material store.Coloring Grout With Acrylic Paint
White grout (for dry indoor mosaic art*) can be colored with artists acrylic paint. You should mix the grout up according to manufacturer instructions, and once you have a nice lump of grout with a consistency similar to dough, you can add the paint. Mix in the paint a little bit at a time until you work up to the color you want. (It’s easier to add than remove, as my father would say.)
Make sure you use white grout because white will be easiest to color. If you find that you can’t get a dark enough color with white grout, then consider starting with grey grout. However, if you start with grey grout, you may find it easier to get a darker color, but it might be less intense than what you got with the white grout.*Outdoor And Wet Mosaics
I’ve not used this on wet mosaics. That doesn’t mean it cannot be done. It only means you should test first and be aware that not all pigments are UV resistant and can fade with prolonged exposure to sunlight.Testing For Outdoor Use
I would test my colored grout by placing a hardened lump in water for a week and look for signs of color leaching or softening. I would use a minimal amount of water and look to see if the water was tinted after a week of soaking.
I would also make a few other lumps for hammer hardness testing. I would have a few control lumps with NO paint added so I could compare their hardness to the experimental specimens. Place the head of the hammer in your hand and press down on the sample with increasing weight until it crumbles. The specimens with paint should be more resistant to crumbling. Definitely email me if you observe anything different.Use Studio Grade Pigments For Reds, Oranges And Yellows.
Use studio-grade or student-grade pigments when it comes to reds, oranges and yellows. The artist-grade pigments of reds, oranges and yellows are cadmium oxides, which are toxic. Studio-grade pigments are generally “non-toxic,” which means there isn’t a known toxic effect in the short term.Acrylic Paint Strengthens Grout
Acrylic paint should improve the tensile strength and impact resistance of the grout the same way thinset is fortified with polymers. Of course, all of this refers to conventional grout and not the new epoxy-based grouts. I have no idea what could be done with epoxy grouts.Should You Color Grout?
The most important question about coloring grout is should you color it.
Consider the following:
Novice artists tend to see the choice of grout color as an opportunity to improve their mosaic. Experienced artists tend to see grout color as a potential to screw up their mosaic and thus tend to make a conservative choice for grout color,
Grout color should contrast tile colors not match them. Unless you are using gray tile or light blue tile, a medium gray is usually the best choice of color because it tends to contrast the most colors. If you match grout color to tile color, then your tiles won’t be separated visually, and the mosaic effect will be lost.
The grout line is best used to separate the tiles visually and not as a color field. Think about how a thin pencil line provides definition to watercolor paintings but not color. That is how grout is best used.Wrong Color Grout?
If you realize that you chose the wrong color grout, I wrote an article on fixing grout mistakes, including wrong colors.Test Color Of Hardened Grout Before Applying To Mosaic
Of course you should test the color of your mix before applying the grout to your mosaic. By test, I mean mix up a small amount of grout and color it and allow it to harden overnight. You need to know what the grout looks like when it is hardened and dry before you even consider applying it. Keep in mind that grout always looks less intense and lighter after it has hardened.
If you are worrying about wasting a little grout and paint by testing it in this way, then consider how much you will waste if you apply it to your mosaic and it isn’t right…
This is not a straightforward question because most of the grout does not end up in the gaps between the tiles. Instead, there will be some grout on the sides of the mixing bucket, on the mixing tools, on your gloves and last but certainly not least, on your worktable or floor. This last place is where most grout tends to end up, depending on the skill and experience level of the artist doing the grouting. However, with a little forethought and planning, even a novice can minimize the amount of grout wasted in this way.
Before I explain some practical ways to use grout efficiently, it’s worth the time to talk about what is theoretically possible if all the grout ended up in the gaps.2 Pounds Per 10 Square Feet THEORETICAL
If you are doing large mosaic walls instead of smaller mosaic plaques, then you could THEORETICALLY gout 10 square feet of 3/4 inch glass mosaic with a 1/16 inch grout gap with under 2 pounds of grout, but again, how much grout you actually consume will depend more on your work methods than anything else. Also, the smaller the project, the more grout you will use per square foot because grout tends to be wasted at the edges.Practical Numbers for Novice Artists
If I were to propose a rule of thumb for artists grouting small projects, I would say 1/2 pound to 1 pound per square foot, provided your grout gaps are 1/16 inch.
Here’s a better rule of thumb for novices:
A little wasted grout is better than a wasted mosaic.
The last thing you want to happen is run out of grout before you finish grouting the mosaic. You also don’t want the grout to start drying out before it can cure, and this is more likely when the grout is mixed up in small batches under a pound.Sanitized For Your Protection: Plastics Are The Solution
Grouting requires that you smear grout to the edges of the mosaic and work it in so that inevitably a lot of grout falls off the sides of the mosaic and onto whatever you have beneath the mosaic. If the wet muddy grout falls onto a clean surface, it can be scooped up and reapplied to the surface of the mosaic. If it falls onto the floor or any other surface likely to have traces of dust, lint, hair or other contaminants, then it is best to discard what fell.
At our studio, we keep rolls of construction plastic and use this to cover our worktable before laying the mosaic on it for grouting. You can also use ordinary kitchen plastic wrap such as Saran Wrap to wrap your table. (Note that wrapping may be easier and more reliable than merely trying to tape or tack a layer on top of the table, which tends to get pulled up in all the activity of grouting.)
We also make sure that the worktable we use is large enough so that we have at least 6 inches of surface beyond each edge of the mosaic. This is important for making sure that we can scoop and reuse the clumps of wet grout that inevitably fall of the edge of the mosaic, but also for making sure that we don’t have to stop and clean up a mess on the floor before we step in it.Misting Spray Bottles & Humidifiers
You should never add water to grout once it is mixed up, and you should not wipe the surface of a freshly grouted mosaic with a rag that is too damp because you can leach the pigment out of the grout.
However, it is important to keep the grout from drying out as it cures. For this reason, we often mist the air around our mosaics as we are grouting to make sure the air isn’t too dry if the heat or AC is running. We also run a humidifier if conditions are particularly dry. These same precautions can help extend the life of clumps of wet grout so that they can be reused.
If you ever pick up a wet-looking clump of grout and find that it has started to form a stiff crust on the outside, then it is best to discard it. Misting spray bottles and humidifiers will help prevent this from happening as quickly.Putty Knives (And Serving Spoons) Used In Pairs
The main reason so much grout is wasted in the bucket is that it tends to get splattered and streaked up the sides of the bucket where it starts to dry out, and most people don’t notice it until it’s too late to do anything about it. The key is to be disciplined and remember to scrape down the sides of the bucket during mixing and immediately afterward, and after each time you scoop out some grout or do anything that smears it up the sides of the bucket. Try to keep your grout all together in the bottom of the bucket like a lump of dough.
A putty knife with rounded corners or an old serving spoon from the thrift store are good tools for scraping the grout into a lump, but you should always have a pair of these tools instead of a single tool so that you can use them to scrape grout off each other.
The grout removal tool we sell is typically used to remove grout from between glazed ceramic bathroom tile, but it can also be used on mosaic art made from small pieces of glass. Dental picks and small screwdrivers may be more useful when the tesserae and grout gaps are smaller, such as typically seen in figurative mosaic art.
Here are some tips for removing grout using the grout removal tool and other scraping tools:Always do the work wet. Use a spray bottle to mist your work area and reapply as needed. Scratch the surface of the grout to break through any invisible pore sealers. Re-wet the grout by misting again. Allow the water to soak in. Wait at least 5 to 10 minutes and re-wet. Do not let any crumbled grout go down the drain if working in a shower or bath. Even in powdered form, it is still concrete and will accumulate and plug low spots in the plumbing. If you are working in a shower or bath, plug the drain and scoop out all the material with a spoon. We call them work spoons at my house. Make sure you explain to the spouse that they came from the thrift store and not the kitchen.
A common mistake made in first mosaics is a variation in the width in gaps between the tiles which results in the details of some areas being “lost” in concrete once the mosaic is grouted. The problem is a little sneaky because it isn’t visible until the mosaic is actually grouted, and so an artist can be experienced in other media and still get caught by this. In my opinion, it is one of the most subtle points in the mosaic learning curve.
Consider the detail in the photograph below:Rose detail from artist Dorothy Stucki’s “To Begin and End with Nothing”
The artist wishes to depict the angularity and variability in the shapes of the rose petals, and has done good job in doing so. However, some of the gaps between the petals are almost as wide as the tiles. This means two things in terms of how the mosaic will look once grouted:The rose will not be as colorful because once the gaps are filled with concrete, about 50% of the surface area of the rose will be dull concrete at the same height as the red glass and just as visible. Gaps don’t look nearly as wide when unfilled. That is the crux of how the problem sneaks up on experienced artists. The rose will look conspicuously different from the tiling around it because it will be the only place where the surface area contains so much concrete.
The good news is that the problem is easily fixed. I have written an article about how to remove and replace glass mosaic tile to change a design before grouting.
Another relevant point is the importance of displaying and studying your mosaic before you grout it.
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.Crumbling Grout
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.Rounded Tops
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.Solutions
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.
If you have already grouted your mosaic, you can still use these instructions, but you will first need to remove the grout using a grout removal tool, which is normally used to scrape grout from the gaps between glazed ceramic tile. It may take a little more care with glass, but this tool can be used to remove grout from mosaics made from small pieces of glass tile.How To Remove and Replace Glass Mosaic Tile A Caveat
Glass tile doesn’t usually pry up in one piece. If you are able to get most tiles off in one piece, then there was probably something wrong with your adhesive or mortar. Expect the glass to come up in sharp pieces and slivers and not be reusable. Never chisel the glass off by banging at it forcefully. If your scraping tool slips past the tile being chiseled, your knuckles and wrists will be headed straight toward razor sharp teeth mounted in concrete. Wear leather work gloves. I wear my welding gauntlets.Moisture Helps
If the mosaic in question was made with a white PVA adhesive such as Weldbond, then I use a moistened cotton swab to selectively wet the edges of the tile, taking care not to wet the surrounding tiles too much. Note that if the Weldbond has had several months to cure, it may be more water resistant, but you should still apply water. Keep plastic kitchen wrap such as Saran Wrap over the tile and reapply moisture as needed to let the glue soften for an hour or two.
If the mosaic is an outdoor or wet mosaic made with thinset mortar, moisture doesn’t really help. For thinset mortar, it is best to make any changes within a week at most. Thinset is hard and tough and it really grips the glass once it has had a chance to fully cure.Prying Tools
I usually use a medium size standard screwdriver to pull the tile up with a combination of scraping and prying. Notice that when you attempt to pry the tile up, you tend to use the surrounding tile as a fulcrum on which to rest the screwdriver, and this is a problem. It can crack or even shatter the surrounding tile, and it is likely to do so because the glue is usually stronger than the glass. Fortunately, there is a simple solution: Lay a Popsicle stick or ruler over the surrounding tile and use that was your fulcrum. Of course, you will need to use one hand to keep the ruler from sliding back slightly as you pry. If you let the screw driver slide the ruler away, it will make contact with the tile underneath and damage them.Damage To Backers
Plywood and concrete backer board aren’t as strong as Weldbond and thinset mortar, so they will sometime delaminate when use start prying and scraping and you end up pulling off the top layer of the backer. If this happens, don’t panic. Plywood can be patched with a mixture of sawdust and Weldbond, and concrete backer board can be patched with thinset mortar. However, you can minimize the possibility of this happening in the first place by attacking the tile from multiple angles instead of just working from one side.Safety Requirements
When you pry up glass tile that has been glued down, sharp pieces can break off and go flying across the room. (I try to keep my leather work glove over the tile to prevent this possibility.)
You should wear safety glasses with side shields. You may even want to wear the plastic safety shield masks that are made for working with power tools. You also want to make sure anyone else around your work area has proper eye protection.
Another issue is the tiny sharp slivers of broken glass. Keep a vacuum nearby and use it periodically to clean the work area. It is always the tiny invisible slivers that cut you when you wipe the work surface clean with your hand. Use a vacuum instead.
Wear leather work gloves and be cautious of jabbing forcefully at the tiles. Use deliberate motions and think about where your hand will be headed if the tool slips off the tile: The freshly broken glass is sharper than any steel razor and it is mounted. If you punch your hand or wrist into it, you will be going to the emergency room in all probability.