How To Fix Grout Mistakes

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.


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.







95 responses to “How To Fix Grout Mistakes”

  1. […] you realize that you chose the wrong color grout, I wrote an article on fixing grout mistakes, including wrong […]

  2. Beth Avatar

    My handyman grouted uneven1x1 inch marble tiles. Because they were uneven the grout does not come up to the edge of the tiles. I am concerned about mildew etc. getting into the grooves. Can he add more grout to fill up the deep grooves? The grout was applied 48 hours ago at least. I need advice. I would have worked it in with my fingers or moist stiff sponge to deal with the irregularities and then carefully wiped the access grout away. But, now what can be done? If he mists the old grout to moisten it again could he apply a second round of grout without it cracking? Help!

    1. Joe Moorman Avatar

      It’s best to email websites instead of using blog posts if an urgent reply is needed.
      After 48 hours, the grout is more or less completely cured.
      It would probably be best to scrape out the grout with a grout remover and reapply if the grout isn’t sufficient to fill the gap,
      but it is normal to have the grout slightly less than flush with the face of the tile.

  3. Bonnie Wilkes Avatar
    Bonnie Wilkes

    I am about to do a mosaic piece upon which I plan to place pearls and other jewelry. How can I grout this piece without having the grout get into the crevices of the jewelry?

    1. Joe Moorman Avatar

      I have seen people use things like wax and masking tape to seal off pieces with crevices while grouting. My approach is to grout things and then get the wet grout out with a dental pick and tooth brush. However, things like pearls might be damaged by grout. When I make things that might be damaged by grout, I press the materials into a bed of thinset mortar so that the mortar comes up the sides of the pieces/tiles, and then I don’t have to grout. That was how I made the River Map and the Solstice Door.

      1. Gypsie Huntley Avatar
        Gypsie Huntley

        I have used dry grout and brushed it into where I wanted it when I have very delicate things I use in mosaics. Then I use a spray bottle of water and mist the grout until it has enough water. It takes patients and time..bu it works and is a very clean way to grout.

  4. fusedglasz Avatar

    Hi…I just made a mosaic frame with tiles.The frame is made of wood and I used tiles and garden stones. After grouting, I noticed that there were cracks in the grout. I used unsanded grout, so maybe I did not mix it correctly. But is there a way to fix this?

    1. Joe Moorman Avatar

      If the grout is crumbly, it should be scraped out and replaced. We use the that we sell, but you can use a screwdriver or other metal tool, whatever works. You need to make sure you use adequate water and not allow the grout to dry out while curing. Remember that concrete products harden by binding water, not by drying out. If your gaps are larger than hairline cracks, you need to use sanded grout. I hope this helps.

  5. Mary Avatar

    The glass mosaics that were placed on my kitchen are too dark and the grout is dark too… so I bought white grout . before applying it do you think it is possible to apply white grout on top of the taupe grout that was installed? or would it be better to paint the grout white?
    thanks for your reply

    1. Joe Moorman Avatar


      You can’t go over the top because the grout is already as high as it needs to be in the gap (if properly installed). You can scrape the grout out with a grout removal tool or paint it with artists acrylic paint. However, the paint will not stick if the grout has already been sealed. I recommend removing the grout and regrouting if you want to do it right because the paint will eventually start to peel in a kitchen (damp) environment.

  6. Rose Ann Arteaga Avatar
    Rose Ann Arteaga

    I have recently grouted my mosaic with ivory grout and the pieces of glass do not stand out. However, I already sealed it and then I put a coat of clear shellac over it – soft coat. I want to redo the grout by regrouting or painting. Can this be done at this stage?

    1. Joe Moorman Avatar

      You need to find out how to remove the clear coat first. Find the package and do some online research on removing whatever type of material it was, probably polyurethane. Then you can use the information in this post to go from there. I hope this helps.

  7. Liz Clare Avatar
    Liz Clare

    I have just mosaiced a large bird bath which was very old and uneven and I used glass tiles. Because the last time when I tiled a bird bath I found the gaps looked very large after I applied the grout, this time the tiles are almost touching each other. Will the grout still be able to penetrate through?

    1. Joe Moorman Avatar

      Yes, but you should take extra care and time to make sure that you are pressing the wet grout down into the gaps. Make repeated passes from multiple directions. After the grout is hardened, clean it with a stiff plastic brush and regrout any gaps or holes you see.

      I hope this helps!

      1. Elizabeth Clare Avatar
        Elizabeth Clare

        Thanks Joe, my birdbath turned out really well!
        I did as you suggested and pushed the grout in from different directions.
        It looks great – thanks.

        1. RAY Avatar

          I just finished a birdbath made with glass tiles. Care to share a photo?

          1. Joe Moorman Avatar
            Joe Moorman

            Please email us a picture. We love to see people’s work!

  8. Holly Avatar

    I’m mosiacing a large 12″ diameter terra cotta pot. I did not do a good enough job getting the grout off ALL the GLASS tiles. I’ve tried polishing with a deemed polishing tip. That usually works for me but, the grout is not coming off the glass. Any help, would be appreciated so much. I used polyend sanded grout. I’m going to try a wet rag again but I need advice. Please help. Thank you!!!!!! Holly 🙂

    1. Joe Moorman Avatar

      I’ve always been able to fix those type problems with a little vinegar and a putty knive/paint scraper. You have to be quick with the vinegar and rinse it off thoroughly because it will dissolve the grout between the tiles fairly quickly. I hope this helps,

  9. Nancy Avatar

    Grouted my first mosaic project. I used premixed grout from the craft store over glass tiles on a small tabletop. I worked the grout from different directions to get it between the tiles. I checked on it after sitting overnight and ugh! There are small air pockets at many of the tile corners. Can I regrout a thin later paying attention to the holes in the original grout? It will be about 24 hours from original grout. Help!

    1. Joe Moorman Avatar


      You can always regrout to fill in voids. The trick for doing this with water-based grouts (not epoxy-based grouts) is to mist the mosaic with water several times and let it soak in so that the existing grout is damp and so does not suck the moisture out of the new grout before it can harden.

      I hope this helps!

  10. Patti Milbourn Avatar
    Patti Milbourn

    I did mosaic glass tiles on a cow skull, Hated the grout color when finished. I applied acrylic paint to the dried grout and it looks way better. My question is can I seal the acrylic to keep it from wearing off? and if so, what do I use ?

    1. Joe Moorman Avatar
      Joe Moorman

      The acrylic paint on grout should be very durable. You could put an acrylc clear coat on top of the paint if you are concerned about wear.

      1. Amy Avatar

        Hoping someone can see this, first time trying mosaic have it on top of a wood table, the dried grout with mosaic shells literally separated from the table cracking…idk what to do. I used Un sanded white grout and the shells are very far apart idk if you can do that or not… basically decorative shells in the corners of the table and a turtle in the middle and the rest grout with a few pieces scattered… can I fix this or what am I doing wrong?

        1. Joe Moorman Avatar
          Joe Moorman

          Hi Amy,
          Please email some pictures to our website, and I will take a look.

  11. Shayla Avatar

    I mosaic glass stepping stones and have made several. It seems like the last few I have made that the grout is “sinking” after cured. Can I go over the grout again to even it out? I use liquid nails and sanded grout the only thing different would be sealer. Would that cause it to sink?

    1. Joe Moorman Avatar
      Joe Moorman


      Traditional Grout (portland cement + sand + water) does not contract as it cures (hardens), but thinset mortar does. I am not familiar with the new epoxy grouts, but I wouldn’t think they would shrink too much because they wouldn’t be useful if they did.

      A sealer wouldn’t cause a traditional grout to shrink. Are you sure the reduction in grout isn’t due to erosion?

  12. Teri Barker Avatar
    Teri Barker

    I did a kitchen backsplash of mosaic tiles on the bottom and stone on top. The grouting went fine, and looked nice. When I was done I wanted to make the glass shine in the mosaic, and the color of the stone beautiful, like when it was wet. I tried to use a matte seal, but it made the mosaic dull and did not bring out the color of the stones. The man at the store said the high gloss sealer would do the trick, but now it’s way too shiny, it detracts from the stone color?

    1. Joe Moorman Avatar
      Joe Moorman


      An ENHANCER is the type of sealer to use to bring out the natural colors of the stone. You need to go to the building material store and buy some sort of stripper for the gloss sealer. They sell things like acetone and mineral spirits and some water-based strippers that are very effective on paint and varnish. To find out what you need, you will need to search Google for strippers for the sealer you used, which might be a polyurethane. You can search Google for the brand name and then read the description to figure out what it is chemically.

      I hope this helps!

  13. Chad Avatar

    I have 1 x 1 tiles on 12×12 sheets. The tiles are mostly a beige colour with some brown tones. I used a brownish grey grout “oyster grey” qnd this stained the tile what looks to be 5 shades darker. Please help how can I fix this mh backsplash looks brown now and makes me kitchen look completely different. I did not seal the tiles be free grouting.

    1. Joe Moorman Avatar
      Joe Moorman

      You could probably use muratic acid such as masons use to clean concrete from bricks. It is sold at building material stores. Make sure you read the label and follow the manufacturer’s usage and safety recommendations. Wear safety glasses and be careful scrubbing with a brush because that slings micro-droplets of acid.

      I hope this helps!

  14. dorothy Avatar

    hi this is my first attempt at a pebble backsplash.I hand picked rocks from the beach and applied them on to a mesh and then put thinset on the wall .I have uneven pebbles some are higher in height and iam really not sure if i should seal them first for a wet look which i want and then grout.Most of the pebbles are colorfull and iam not sure what color grout to use also how will i grout since some are larger than others.Personally i am a little scared since this backsplash is very large and i feel intimidated about the next step ,perhaps you can give me some advice thank you

    1. Joe Moorman Avatar
      Joe Moorman


      You are right to be apprehensive or a little concerned because grouting an irregular surface is completely different from grouting a surface of flat tile. However, it can be done, and it can be done with little stress if you plan ahead and know what is involved.

      First, you should seal the faces of the stones with multiple applications of an ENHANCER type of sealer, such “511 Seal and Enhance Stone Sealer and Enhancer” and wipe away the excess. Actually, that won’t give a glossy wet look, so you might want to use some sort of gloss polyurethane sealer, but I am unfamiliar with those and don’t recommend them. (For example, I don’t even know if grouting might scratch them up, but I suspect it is a real possibility.) I prefer an invisible ENHANCER type of sealant, which will deepen and enhance the colors and prevent grout from staining the stones. If you decide to pursue a gloss sealer, it won’t be in the mosaic department, but it will probably be in flooring. You can ask how resistant it is to scratching and make a decision based on that, and by searching Google for the product name and scratching or scratch resistance. Whatever route you choose, please let us know what you learn.

      Found beach stones are usually very porous and highly susceptible to grout staining, so pre-sealing before grouting is important.

      The grouting process is different from grouting a flat surface, and it is best done with a gloved hand. We sell thick grouting gloves designed for this purpose.

      Grouting using a gloved hand is more or less sculpting wet concrete with your fingers. The more narrow the grout gaps, the easier it is because wide gaps tend to get accidentally eroded out.

      The following may seem like extra work, but it will save you work and stress in the long run:

      Take a scrap piece of plywood and attach some stones to it using thinset and practice grouting on that. That way you can discover any problems with your method before you put the backsplash at risk. You can also test whether or not you have the stones sealed well enough to prevent staining.

      I hope this helps!

  15. Sandy Johnston Avatar
    Sandy Johnston

    We installed 2 beautiful tumble stone medallions on our stairs landing. The problem is the grout stained the stone and so far we haven’t been able to remove it. It basically ruined our beautiful medallions. Any tips on how to remove the stain and bring the colors back? Please help me.

    1. Joe Moorman Avatar
      Joe Moorman


      The grout only penetrates the top layer of the pores. I would try using 120 grit sandpaper to remove the stain followed by 220 grit to hone it back to a nice finish. I use piece cut from sanding belts (sold for belt sanders) instead of sandpaper because the belts last many many times as long as sandpaper, especially when you wet sand, which is recommended to control dust.

      I hope this helps!

  16. Anna Protheroe Avatar
    Anna Protheroe

    I bought light sea-green mosaic glass/marble tiles in 1 sq ft sheets for my bath/shower area. The light grey grout has turned the green mosaic into a grey-blue colour. Is there a paint or product that I can use on the grout to make it much lighter, or white?
    thanks very much for your site; very helpful

    1. Joe Moorman Avatar
      Joe Moorman

      I’m not sure if you are saying the grout stained the marble, or if the overall color impact is now wrong. Polished marble shouldn’t stain, but tumbled marble should be pre-sealed with a tile and grout sealer before grouting.

      If you are saying that you don’t like the grout color, then you should remove it with a grout removal tool. If you chip any marble tiles during this process, you can replace them with individual tiles from leftover sheets, which is just another example why it pays to buy slightly more than what you need instead of trying to hold to an exact calculation. I’m not aware of any product that could change the grout color, and I would not recommend any kind of paint or coating since this is a shower.

      I hope this helps!

  17. Anna Protheroe Avatar
    Anna Protheroe

    Sorry, I should have added to my post that the grout has not been sealed… but was done several weeks ago ; thanks again

  18. Paj Tognetti Avatar

    Hi. I did a ceramic tile (plates) on a wood (sealed) shelf. I used Weldbond universal adhesive to attach them. I wanted a white grout, so I was unsure about adding sand-for a sanded grout or leaving it as is-as an unsanded grout. I live in Italy, so not much choice in art supplies. After much research, I went with adding the sand, as everyone seemed to for a more durable and lasting grout. As I mixed my 3 parts sand to 1 part white grout powder, then slowly adding the water, I realized that it was looking way too ‘sandy’ and less white. So, I started adding much more white grout to the sand ratio to give more of a whiter look. Needless to say, the grouting part went fine. The problem I am having is that the finished grout still looks way too sandy, with dark specks in it. Not sure how to use a sanded grout for durability when I really like a more clean white (or light colour) grout in my finished mosaic piece.
    What are my alternatives?
    1. Wait until the grout fully dries, then paint over it with a white acrylic paint? In which case, could/should I use a grout sealer over it or leave it as is? Or
    2. Wait until the grout dries then regrout with just the white grout-maybe a thin layer of it will help cover up the sand specs? Then when dry, use a grout sealer for protection, or since it’s for an indoor mosaic, it isn’t necessary?
    In the future, regardless of the space between my tiles, if I am doing an indoor mosaic project (not a floor), and I would like smooth, clean grout color, should I just mix the grout powder with water and grout-leaving the sand out, then seal the grout for durability verses using a sanded grout? Or do I still use the sand but have to also mix into a white grout more white acrylic paint??

    Thank you for your help!

    Paj Tognetti

    1. Joe Moorman Avatar
      Joe Moorman


      Some people report using non-sanded grout without any problem, but most of the emails we get from people having problems with crumbly and cracking grout are concerning mosaics where non-sanded grout was used. As you have seen, it is very important that the color of sand used matches the color of the grout. White grout needs a white quartz sand, but finding the exact color of sand you need can be as difficult as finding the right color grout. If your mosaic is dry and indoors, the grout can be painted with acrylic paint, which should wipe off the glass tile and stick to the porous grout.

      I hope this helps!

  19. Heidi Avatar

    Left my grout on too long and now my glass mosaic tile looks a a little kid coloring out of the lines and completely uneven.

    Water and a sponge at this point is going no where and scraping it with a small knife is still going nowhere. There has to be something I can wipe down with that will dissolve away some of the excess with less effort to expose more of the rounded nice corners.

    Please help,


    1. Joe Moorman Avatar
      Joe Moorman


      It all depends on whether or not you used traditional grout made with portland cement that is mixed with water or if you used one of those new epoxy-based grouts. I can help with traditional grout. Traditional grout can be dissolved with vinegar. I have used vinegar to clean up grout stains in the same way that masons use muratic acid to remove cement stains from bricks. You need to work relatively quickly and make sure you rinse away any residue thoroughly to make sure you don’t damage the grout down in between the tile.

      I hope this helps!

  20. Kristin Avatar

    I didn’t see my problem listed even after reading the comments I am hoping you will see this and can help!
    I am completing a mosaic tile table for an auction project for my elementary school. We used adhesive to glue the tiles down and I grouted it literally 30 minutes ago.
    Problem: Some of the tiles popped off as I was scraping the grout! I tried to place a few back but when I went to wipe off the excess grout with a sponge pieces were still falling out!
    What should I do? Let it dry and fit a few pieces in and regrout? I’m really at a lost.
    I’ve never used mosaics before and bought the premixed grout from hobby lobby.

    1. Joe Moorman Avatar
      Joe Moorman


      It sounds like the problem is the glue not the grout. I’m fairly certain. White PVA adhesives such as Weldbond do not bond to formicas and plastics and painted surfaces, and so a “glue problem” is often an inappropriate surface problem. You can also have a problem with tiles popping up while grouting if you try to grout before the glue has fully cured. For this reason, I like to wait several days before I grout. I also like to spend a few days looking at the ungrouted mosaic so that I spot any glue residue or last minute changes.

      1. Kristin Avatar

        I see your point!
        I wish I could send you a picture. I guess since I started to grout it was too late to reglue the tile. I had waited a full week after the glue but I assuming my students did not apply enough. I was worried too much would be applied and the tile would be uneven.
        I went ahead and tried to place the tile back in and I let the grout sit. Tomorrow night I am going to do the final touches and clean of the haze. Any suggestions on best way to remove the last bit of excessive grout and haze?
        🙁 I have to turn in our project Friday. Fingers crossed everything comes out good!

        1. Joe Moorman Avatar
          Joe Moorman

          Hi Kristin,

          Hazing can require a bit of rubbing with damp and dry cloths, and so you might still get some tiles that pop off. If so, you will have to reglue them. Grout doesn’t have strong adhesive properties like mortar, and so you can’t use it to mount (attach) tiles.

          1. Kristin Avatar

            Thank you for such a quick response!
            So it’s okay to reglue even if the grout has started to set?

          2. Joe Moorman Avatar
            Joe Moorman

            I have re-glued a tile during grouting, but it didn’t work very well. Grouting requires a lot of wiping and cleaning, and that doesn’t work well if the glue isn’t firmly cured. What you will probably end up doing is gluing that one tile and letting it dry and then regrouting around it.

  21. Cindy Avatar

    Thank you for this article. I am new and really worked hard on a picture of my cat. Looked fantastic until the white grout went on. I’m on the fence about painting or removal. Then I’m stuck with making a decision about what color will work best. I’ll have to think for a while….

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Cindy,
      If your mosaic is dry and indoors, you can wipe artists acrylic paint on a mosaic and wipe it off. The paint to color the grout but wipe off the tile. You can also scrape out the grout with a grout remover:

    2. Cindy Faith Avatar

      Hi Joe. I just now saw your response. Thanks

      Would using a black sharpie work. My background is black shiny tile and the white grout in between washes out my cat. Hmmmm.

      Here’s link to picture.


      1. Joe Moorman Avatar
        Joe Moorman

        Hi Cindy,

        I suppose a black sharpie would work fine, but I don’t think it would be archival and resist fading over the years.


  22. Cindy putman Avatar

    Why does grout seep between my mosaic glass and the vintage window glass? And why does it take forever for my adhesive glue to turn clear. Some pieces still have milky white areas.

    1. Joe Moorman Avatar
      Joe Moorman

      If there is a void in the glue between the tile and the glass you used as a backer, then the grout can press into the void. White PVA mosaic glues such as Weldbond take a long time to dry when sandwiched in between two pieces of glass. For that reason, you might want to use silicone for these glass on glass mosaics. Note that we don’t recommend silicone for traditional mosaics.

  23. Meredith Avatar

    Hi Joe,

    Thank you for posting these tips. I just did my first mosaic on a coffee table and struggled with grouting. The grout is textured and bumpy in places. How can I disguise those flaws? I thought perhaps I could paint the grout with acyclic paint? I probably can’t grout over already dried grout?

    Thank you!!!

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Meredith,

      The grout of dry indoor mosaics can be painted with artists acrylic paint. You can also scrape out the grout with an old screwdriver or grout removal tool and regrout. Make sure you mix grout thoroughly with adequate water to prevent these texture and consistency problems.

      I hope this helps!

      1. Meredith Avatar

        Thank you Joe!
        I used Modern Options Mosaic Grout from Michael’s, so it was pre-mixed. Do you advise against adding more grout on top? There are some areas that do not have quite enough grout and other areas where I could scrape away some before adding more. Do you think it would be a mistake to purchase a different kind of grout to do this last layer?
        Thanks so much!

        1. Joe Moorman Avatar
          Joe Moorman

          Hi Meredith,
          We don’t use the modern epoxy-based grouts. We only use traditional portland-cement grouts. I would scrape out the old before replacing with new, but I don’t know how feasible that is with those new plastic-like grouts. I so wish people would avoid craft stores and people who market heavily on the word “craft. They don’t vet their products well enough from what I have experienced personally and from what many other people have told me. I once had a customer grout his mosaic, and the glass gems he purchased from a chain craft store turned out to be clear glass with a cheap color coating that came off in the grouting process.

          1. Meredith Miller Avatar
            Meredith Miller

            Hi Joe,

            I am not sure it is epoxy based…I was able to clean off a lot of grout that remained on the tiles with vinegar, which I used because of your recommendation in another post. Do you think that means it’s not epoxy based?

            I am so exhausted by ths project that regrouting is really daunting. I am hoping that maybe the vinegar means it’s not epoxy and I can spead a thin layer of new grout over the old grout?
            Also what do you think of caulking a thin layer over the old grout?

            PS I wish I had found your site at the beginning of my project!

          2. Joe Moorman Avatar
            Joe Moorman


            I’m not sure if it were epoxy or not. Epoxy grouts might contain some traditional lime at least for color and body, but I suspect if vinegar cleaned off any thick residue, it wasn’t epoxy. On the other hand, it is definitely something other than traditional grout if it came wet in the package.

            If regular grout can stick to it, I suppose you could cover it with more grout. Caulking probably won’t look right.


          3. Meredith Avatar

            Thank you so much Joe for being so generous with your knowledge. I appreciate it!

  24. Mary Avatar

    I used a transparent yellow glass in a mosaic project with thin set and a charcoal grey grout. During the grouting process, some water seeped in behind the yellow glass and now there are grey shadow areas. Everything is down pretty tight. Is there any way to loosen the piece, remove it, and start again?

    1. Joe Moorman Avatar
      Joe Moorman

      I doubt you could loosen it by prying without breaking the glass. You could use vinegar to dissolve the thinset and reapply that piece.
      I hope this helps,

  25. Audrey Baas Avatar
    Audrey Baas

    I have stained glass a bowling ball. I used a sanded grout but I either wiped
    Too much off and now there are too many sharp edges. Can I regrout the
    ball so it will be more even and cover the edges more so the tiles will be
    more even with the grout.

  26. Rebecca Avatar

    I have created a pique assiette mosaic picture frame using Portland cement based grout. However, the died finish of the grout is not as smooth as I would like. Is there a method by which I could sand or smooth down ridges and bulges in the grout without damaging anything?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Rebecca,

      I have used a marble file to grind down bulges in grout and thinset, but the abraded surface will look different from the surrounding grout. You also have to be careful not to scratch or knock loose any tiles. To make things look uniform once you are done, you could consider painting the grout with artists acrylic paint in a matte finish. The paint should wipe off the smooth tile and stick to the rough grout, and so it is fairly easy to do. The only advice I would give is to use a color mixed with a little white instead of a straight color so that the color isn’t too intense. Grout is usually not as bright or intense as tiles, and the mosaic will probably look better if you keep it that way.

      I hope this helps!

  27. Deb Avatar

    I’ve just grouted an outdoor mosaic house number and terracotta planter. They looked fine but 2 days on and cracks have appeared in both and spoilt them.

    I sealed them for outdoors. I used good quality mosaic sanded grout, I added oxides and mixed with mosaic waterproof additive. I’m working outside. Wondering what went wrong.

    How can I remedy this without dislodging some tiny mossics? Is it possible to grout over the existing grout or not? Some advice would be greatly appreciated.

    Many thanks


    1. Joe Moorman Avatar
      Joe Moorman

      Hi Deb,

      I am thinking that it was the waterproof mosaic additive that caused the cracking. We have never had that problem with traditional sanded grout.

      It is extremely difficult to impossible to remove grout from a mosaic made from very small tile or tile pieces.

      I recommend grouting over the existing grout and pressing the grout down into the cracks thoroughly using repeated passes and rubbing.

      I hope this helps!

      1. Deb Avatar

        Hi Joe,
        Thanks for the reply. I think you’re right about the additive. I’ve never used it before and won’t be again.

        I’ve done as suggested and regrouted over the top. So far so good.

        Thanks for the advice. Appreciated.

        Kind regards,

  28. Laura Avatar

    I just put grout on a mosaic where I had painted the tiles. I had sealed them and everything but all of my color rubbed off now I have a plain white batch of grouted tiles with no color is there anything I can do?

    1. Joe Moorman Avatar
      Joe Moorman

      Nothing other than repaint them. I would probably use a different type of paint because even though grout is abrasive, it should not have rubbed all the paint off if there was any kind of real bond between paint and tile.

  29. Claire Avatar


    Can you help? I’ve recently started mosaics – made a few things i have been pleased with. some of them have been to use/ display outdoors – i used a various things to seal and waterproof them, but it always stains the colour of the grout making it look like it has been tea stained! I used an expensive epoxy that was recommended for this type of thing and have tried clear yacht varnish.

    Is there anything you could recommend?

    1. Joe Moorman Avatar
      Joe Moorman

      A standard silicone-based Tile and Grout Sealer is the only thing to use.

      1. Claire Avatar

        Thank you, Joe.
        I’m assuming that as it is specifically for sealing tile and grout, it will not discolour the grout.

  30. Maggie Carey Avatar
    Maggie Carey

    Hi, I have grouted several of my mosaic art projects with sanded grout and several have small cracks in the grout. This is the first time I’ve had this problem. I am using Polyblend grout. It doesn’t seem to be crumbling or flaking. First, did I use too little water or did it dry too fast? Can I grout over the cracks? In some places the grout was quite thick because I was doing pique assiette and the tesserae is all different heights.

    Thanks for your help

    1. Joe Moorman Avatar
      Joe Moorman

      It sounds like you had some wider gaps or didn’t get the gaps packed well enough, or possibly there was too much water in the grout. The grout should be like a firm dough. The good news is that you can press grout into cracks.

      I hope this helps!

      1. Maggie Avatar

        That’s good news. I will give it a try and hope for the best! Thank you for your time and for a great, informative blog.

  31. Cindy Avatar

    Hi Joe,
    I just grouted my mosaic garden bench. So many hours of work, and now the grout is to light and my work looks washed out….. I am very upset.
    I can only concluded I used a bit to much water when mixing. I have used this grout before and the color was fine.
    If I buy and apply this product (Polyblend #60 Charcoal 8 oz. Grout Renew Colorant), can I still use the bench outdoors?
    I am hoping this will solve my dilemma as I am really rather heartbroken over the grout drying so light.
    Please advise, and thanks once again.


  32. Eliza Avatar


    I have been working on a mosaic project with my students and have just got to the grouting stage. I have realised (after applying the grout) that the colour is too light and takes away from the beauty of the coloured tiles.
    If I apply acrylic paint to the mosaic to create a darker coloured grout, would you suggest I thin the paint with water or another substance to allow it to spread across the whole mosaic? Or do you apply a thick layer of the paint straight from the bottle?
    OR Would you suggest I colour a small batch of grout and re-grout on top of the current white grout?

    Thanks for sharing your expertise!

    1. Joe Moorman Avatar
      Joe Moorman

      The following article has a section explaining how to change grout colors with acrylic paint if you don’t like how it turned out:

  33. Terry Avatar

    Hi Joe! Thank you for this info .. great site! My question is this: I have just finished a very large mosaic on an exterior block wall. I use both vitreous glass tiles and stained glass scraps in the project. I grouted it with Mapei sanded grout, but now that is is dry, I think the color is too light, and I am unhappy. I have read lots of places about using acrylic paint as a stain but they all say for interior only. I could use a penetrating sealer, but I don’t think it would darken it enough to make me happy. The grout dyes I have found seem like they just paint the surface of the grout and may wear off. (They also may be for interior use only.) So is there another option that I am overlooking? Something that would darken the grout, and last in an exterior application? I thought of mixing oil paints with linseed oil (I used to do this with wood carvings and it worked great.) but I am not at all sure it would work on grout. Any advice would be appreciated!

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Terry,
      This is an opportunity to do an experiment, one that could help a lot of people, and I think the risk is low. My inclination would be to use some sort of oil-based paint, and if these paints were made exclusively with mineral oil, there would be no problem according to what I have read. The problem is that most artist-grade oil paints contain vegetable oils such as linseed, and these oxidize and form radicals that disintegrate concrete.

      Your first step would be to find oil paint that is made from mineral oil, which might not be that difficult. I have made a grout and marble stain for my marble engravings by pulverizing sticks of oil pastel and mixing in mineral spirits and mineral oil. I’m sure the pastel sticks contained some vegetable oil, but I figured the overall content of what I made from them was relatively low.

      Your second step would be to test what you find or make on a piece of scrap.

      If you pursue this, please take pictures. I am sure there are many people who are trying to solve the same problem.


  34. Christa Wurm Avatar
    Christa Wurm

    My son’s school recently completed a multi-panel mosaic. There are a few images of the wrong color. It was done by a traveling artist who lives hours away. How can we best remove, replace and regrout the images to look good with the rest of the piece?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Christa,

      Email me some pictures, and I will take a look.


  35. Kelsie Avatar

    I recently put up frosted glass tile, and the grout “haze” seems like it’s pulling off the frost making it look like it has water streaks.. any help on fixing solutions?

    1. Joe Moorman Avatar
      Joe Moorman

      I would wipe it with a rag soaked in vinegar and quickly rinse it off before the vinegar can eat the grout. First I would try scrubbing/buffing with a wet rag. Of course, all of this assumes you used traditional grout and not a new epoxy grout.

  36. Robin Richardson Avatar
    Robin Richardson

    Joe, thanks for all you guidance. I have a lot of questions so I’ll list them. My photos will follow. The sun is abt 2.5×2.5ft. Their are just 3 rays and the head grouted. I stopped when I saw the result in the am.
    1. I was too ambitious and thought I could grout several rays and the head of the eagle in one process. After several wiping down due to haze, the following morning it seemed still hazed and some parts were crumbling.
    Question: How do I remedy this situation. Used Wellbond as adhesive and Unsanded Tan grout and it was still hazed or dull in color and crumbling in places.
    It just didn’t look right( I’ve done almost 25 indoor mosaics but this was the largest)!
    2. I thought the eagle head looked dull; so do you think I can grout over it in black while still leaving the rays in tan? If I do so, I’m afraid the eye won’t stand out.
    3. Can I just scrape off excess grout overhanging it onto the adjacent tile?
    Thanks so much for your assistance. This is a special “Indoor Mosaic Project “

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Robin,

      Please email me pictures using the address on the help page of the MAS website. If the grout is crumbly, it usually means that it died out while it was trying to harden. It needs moisture to harden. In this case, the problem could be that you used non-sanded grout, which is only meant for tiny gaps. I’m not sure what overhang means.

      Please let me know.


      1. Robin Richardson Avatar
        Robin Richardson

        I sent you pics of my sun yesterday via your email address in the MAS Website along with comments. Hopefully you were able to obtain them. Let me know. Thx Robin

  37. Robin Richardson Avatar
    Robin Richardson

    The grout is not smooth in some areas of one part of my mosaic. Can I remove the grout just in these places or due I have to regrout the whole section. Thx Robin

  38. Robin Avatar

    Well, I also noticed most of my tiles .79 inches (20mm) adjacent to each other. It looks great without grout but if I’m going to re-grout ; should I remove all tiles, space them apart and regrout? It’s an indoor lg project. Thx for your help

    1. Joe Moorman Avatar
      Joe Moorman

      Dry indoor projects do not have to be grouted.

  39. Kelly Avatar

    I have just started this art form and made a 10 x 10 mountain/lake scene incorporating a rock wall. I am not happy with the grout in the rock wall and want to add more…will the new grout bond with the old? it will be about 24 hrs between layers. The new layer will be no more than 1/4 inch thick.

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Kelly,
      Yes, grout will stick to old grout. Mist the old grout before working so that the inside of the old grout isn’t dry so that it doesn’t suck too much water out of the new grout.

  40. Deborah L Avatar
    Deborah L

    I grouted (sanded grout) my large clay pot which was sprayed with white primer and glued with Wellbond on Saturday, then left for 5 days. It’s fine except for the top rim. I couldn’t get the grout to stay on. The pot was on a rotisserie-like stand so that I could turn it while grouting without losing the stick out broken plate pieces. When I get back, I’m thinking that I’ll put the pot on a table and add grout to the top rim. I can spray the adjacent grout with water as you suggested for going over grout, but I’m imagining that I’ll just wipe a bit over the edge of dried grout to make it flush. I’ll send a pic.

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