Clear Coatings For Mosaics?

Texture and three-dimensional elements make two-dimensional art much more interesting. Having thicker pieces and pieces that stick out make people want to reach out an touch your mosaic. Why would you want to cover that up with a material that scratches easily, can’t be repaired and turns yellow with age and sunlight?

Even if you do need to cover the mosaic somehow to provide a level surface, there are usually other means of doing so that don’t involve permanently coating the mosaic with these relatively short-lived materials.

My Mosaic Is A Table Top

Most mid-sized towns and cities have a glass shop where you can have a sheet of glass cut to a custom size and have the edges beveled (smoothed and rounded) with a torch. This same shop will also have small rubber pads for sitting under sheets of glass, and you may be able to use these for holding the sheet above your mosaic. If the surface of your mosaic is fairly rough and irregular in height, then you can use larger rubber stoppers and other means of holding the glass above the surface of the mosaic (such as a rim around the table).

I have seen some wonderful mosaic tabletops that were made from all sorts of found stones, shells and artifacts and then covered with a sheet of glass that rested on rubber stoppers. The overall look and feel of the table was like one of those curio coffee tables that have the glass tops over artifact collections, only the artifacts were closer to the glass cover, more visible and seemed to be part of the surface, which they were.

One important caveat: Make sure that the mosaic is evenly supported in multiple places and that no one piece of the mosaic can make contact with the glass if heavy objects are placed on the table. Otherwise you could possibly crack the glass.

My Mosaic Is A Floor

In general, I do not recommend making floor mosaics from materials with different thicknesses due to the potential for them to be a trip hazard and to be damaged by shoes and wheels and vacuums. If you do want to use material of variable thickness in a floor mosaic, make sure you do something that results in a level surface.

Consider Using Mortar Instead

One option is to press these pieces into a bed of thinset mortar similar to how crafters press tile into wet concrete to make garden stepping stones. However, be aware that mortar thins as it cures, so there is only so much height difference that can made up for by mortar when a tile is much thinner than the tile around it. In our studio, we solve this problem by mixing small pea gravel into the mortar underneath the particularly thin tile. We also have thin pieces of stone tile that we coat on both sides with thinset mortar and use as shims under thin pieces. Note that these methods aren’t really practical for large areas or commercial jobs.

Clear Epoxies For Floors

There are epoxy products that will last a long time by standards of flooring and architectural products, but I tend to think in terms of archival standards for fine art and making things as intrinsically durable as the Roman aqueducts. If you put a epoxy clear coat over the top of the mosaic, then you need to carefully review the manufacturer literature on the packaging and Internet. You want to look for information concerning scratch resistance and hardness and durability. You will also want to review the manufacturer’s recommendation for maximum recommended thickness.

Epoxy Not Polyurethane

If you do use a clear coat to make a level surface over a mosaic made from irregular pieces, then make sure you use an epoxy and not a polyurethane. Polyurethanes are not as hard and scratch-resistant as epoxies. They also do not bond securely to glass the way epoxies can.

How To Find Epoxy Clear Coats

These will not be in the tile aisle of the building material store. They are sometimes in the flooring department, but they are more often in the paint department. The important point is that they aren’t specific for mosaic or tiling, so don’t expect them to be sold for that purpose. Also, you should not expect professional installers to know how epoxy clear coats might be used to cover tiled surfaces, at least not in a thickness significant enough to compensate for differences in tile height.

Problems With Clear Coats For Mosaic

  • They cannot be removed or repaired by practical methods.
  • Installation is not very forgiving. You may have bubbles and haze that cannot be fixed.
  • They are not inexpensive and usually cost more than the mosaic tile.
  • They are not commonly used on mosaics, so professional installers don’t have experience with them as far as mosaics are concerned.
  • They scratch easily compared to porcelain, glass and most stone.
  • They turn yellow in ultraviolet sunlight, some much faster than others.
  • They won’t last the millennia that glass and stone mosaics are capable of lasting.

43 thoughts on “Clear Coatings For Mosaics?

  1. Carrie

    I am interested in mosaicing an old window with clear stained glass. My goal is for the colors from the stained glass to throw color into my little nest. Is this possible keeping the backside attractive where the adhesive would be? Would epoxy be the best kind of adhesive to use?

    Reply
    1. Joe Moorman

      Most people use a white PVA adhesive such as Weldbond for glass on glass mosaics. However, it can take quite a while for the glue to dry and be completely translucent when sandwiched between large pieces of glass.
      Thanks,

      Reply
  2. Cindy

    I just finished doing a mosaic on a concrete bench for outside. After I seal the grout lines I would like to put a clear coat of some kind on it. Is that OK?

    Reply
    1. Joe Moorman Post author

      Yes, but you need to attach the tiles with thinset instead of adhesive so that the water doesn’t make them pop off over time. I wrote an article about mosaic bird baths.
      I hope this helps!

      Reply
  3. Doug

    I’m doing some mosaic inserts in some concrete benches. What can I use to seal the tile and grout and not reveal the tiles sharp edges? Clear sealer of some type?

    Reply
    1. Joe Moorman Post author

      Doug,

      Grout or thinset mortar needs to hide sharp edges, not a sealer. Sealers are thin applications the seal pores. I have used small rounds pebbles of a fine-grain stone (found outdoors in different regions of the country) to smooth rough edges between tile when the grout didn’t hide them. The fine side of a marble file such as we sell can be used on outside edges, but it can’t fit between the tile. A small round stone can be dragged down the length of the grout gap and dull any sharp edges higher than the grout.

      Reply
  4. Ann Lebo

    I finished a stained glass mosaic art piece. I included resin peacock feathers
    that I made. I just finished grouting the piece and the resin feathers are not
    level. Could I use ice resin to level them off?

    Reply
    1. Joe Moorman Post author

      Ann,
      I suppose you could, but we are unfamiliar with resin. We only use archival materials and methods.
      Thanks,

      Reply
  5. Naomi LaRue

    I did a “mosaic” of small gravel, some tinted with acrylic paint. It is a butterfly in center of a small round table. The butterfly sections are framed with a soft round rubber. It is surrounded in crushed sea shells. The rest of table top is done in thin pine strips, herringbone pattern and stained with minwax in Honey color. I have not sealed the stain yet. The mosaic has a layer of mod poge over top. I tried to keep the gravel as level as possible with the height of strips. I would like to seal it all with something to create a clear, level finish that is resistant to scratches and water stains. Can you suggest something?

    Reply
    1. Joe Moorman Post author

      I’m not sure what would be compatible with the modge podge and minwax stain and other materials. It sounds like a glass top on rubber feet might be the way to go. I hope this helps,

      Reply
  6. Becky

    Dear Joe: Hi! You have a lot of knowledge here! Thank you! I inverted a glass and mirror tile design on tape and want to put it on top of a wooden box. A lot of the tiles are cut with sharp edges so until I read your blog, I was going to totally cover the tiles with epoxy. This is new to me so I am learning: here is what I have gathered as possible steps: 1. Sand and scratch wood and Seal wood with Weldbond (Weldwood does not hold mirror tiles well but seals wood well). 2A. Glue tile images down (tile images are inverted onto thick celephane type tape that I don’t think will stick to dried epoxy– meaning even if 2B is possible, if the epoxy touches the tape, the tape can be removed after the epoxy dries), glued on top of the dried Weldbond with E6000 OR; 2B. Put a 1/16″ layer of epoxy mixed with Faux Granite-Mauve color (1 part epoxy, 1 part Faux Granite– cool texture look!) over the dried Weldbond and while wet add tile images on the tape so that the colored epoxy seeps up into the 1/16″ to 1/8″ spaces between the tiles, and the Faux Granite then becomes like a grout look. However, I don’t know what kind of epoxy resin to purchase for glass and mirror tiles or if any epoxy resin will hold the mirror and glass tiles down so I am worried about 2B– originally I was going to add clear epoxy resin over this 2B and over all the tiles until I read your blog. I have tested E6000 over the dried Weldbond on wood with my tiles and it is super strong. But I prefer 2B if it is possible because I like the Faux Granite look. I don’t think I can pour the “Faux Granite” colored epoxy resin over the top of the tiles after I glue tiles down with E6000 and remove the tape, because over the top of the tiles might cause too much “Faux Granite” color over the tiles and not just in the spaces between the tiles. 3. If 2B is not possible I will need to grout over the tiles glued with E6000 with colored sanded epoxy grout, I think, one compatible with mirror and glass tiles. Originally I thought I should epoxy over the whole tile image after removing the tape that is over the tile images and after grouting one way or the other because of the many sharp points on the cut 3/8″ glass and mirror tiles. But if grout is sufficient, I think your suggestion is best, to avoid epoxy over the tiles themselves. Can one file the glass or mirror tile point if the point is exposed after grouting? I really thank you for challenging my plans. I have a lot to learn! Becky

    Reply
    1. Joe Moorman Post author

      For mosaics that need extra strength, such as a mosaic on a chest or box, you can use thinset to grout or one of the new epoxy-based grouts. They are stronger than regular traditional grout. Filing clear glass mirror tiles is problematic. Regular vitreous glass tile and recycled glass tile can be filed with the fine side of marble file, but clear glass must be filed more gently because it tends to flake and scratch more, and the flakes are more visible.

      I hope this helps,

      Reply
  7. fred

    Hi there 🙂

    I have a mosaic picture mounted on plywood that I want to turn into a garden table. I don’t want a glass top and it has to be waterproof. Any idea how I go about this?

    My first thought was epoxy clear coat, or do you have a better idea?

    Thanks,.
    Fred

    Reply
    1. Joe Moorman Post author

      Hi Fred,

      For a mosaic to be durable in a wet or humid environment, the first step is to chose a backer and cement that are appropriate. It is very difficult to start with an existing mosaic on plywood and make it durable, but I would use marine varnish/water seal to thoroughly seal the sides and bottom. I would use at least 3 coats, and I would pay close attention to the sides. The face of the mosaic isn’t as vulnerable, but it still needs to be sealed as well.

      I hope this helps.

      Reply
  8. Dave

    I have a mosaic that was produced overseas to a client’s specs. and now some of the individual pieces have fallen out. The attachment method used to adhere the pieces to the substrate is unknown. The mosaic is mounted vertically to a wall. Is there a clear substance that can be applied to the surface of the piece that will keep the individual pieces of glass in place should one or two come loose from the substrate? The coating should keep the pieces together as a unit. I realize this could mean the whole thing could come loose and fall off the substrate but the client is willing to gamble on it. The mosaic cannot be laid flat to allow epoxy to cure the way it could if this was a table. Can you recommend anything? Thanks!

    Reply
    1. Joe Moorman Post author

      Hi Dave,
      We can definitely help. You might be making this more challenging than it really is. You can cement the tiles back into place and use a small piece of clear packing tape to hold the tile in place until the cement cures. The only real issue is to make sure you use a glue or cement that sticks to what is already there. You can test this by pressing a dot of adhesive onto the substrate and allowing it to harden thoroughly and then scraping it off.
      I hope this helps!

      Reply
  9. Lizzie Hughes

    I have a mosaic picture of a lady witth necklaces and bracelets raised above the surface of the mocaic tile. Can I use resin or polyurethane to properly cover the varied levels. It doesn’t have to be level because it is to be hung on the wall
    Many thanks, Lizzie

    Reply
    1. Joe Moorman Post author

      Hi Lizzie,
      The jewelry was raised to give the surface of the mosaic interesting texture, and so I’m not sure why you would want to cover that up, especially on a vertical surface that is decorative. At any rate, the coatings are thin and won’t cover elements that protrude with any significant depth, and so they wouldn’t be effective. I think you should keep the mosaic as is and enjoy the textured elements.
      I hope this helps.

      Reply
  10. Jennifer Blenkinsopp

    Hi Joe,, I have done a mosaic of a woodland scene on a bevelled wood board, The problem I have is in parts of the mosaic I used glass frit which usally bonds in a kiln, it’s in different textures , this frit very close so I cannot grout it , it is glued on the board . Would you just leave the part with frit and grout the tiles , I did think of epoxy resin also , but want the feel of the glass , Do you think I should leave all of it or part grout. .?

    Reply
    1. mosaicart

      Hi Jennifer,
      Indoor mosaics do not have to be grouted, and so if moisture isn’t an issue, anything to make it look right is acceptable. I can tell you that grout tends to overwhelm and cover small chips, and so I would probably leave it ungrouted.
      Thanks,
      Joe

      Reply
  11. Alexis

    I made my first ever glass mosaic top lazy susan, i did not think to smooth the edges of the glass peices before gluing them down. I attempted to sand the edges before grouting but apparently it wasnt enough. I ended up with several cuts on my hand after grouting. I need to put a clear coat of something on it so it wont be dangerous. Any suggestions would be appreciated. Thanks

    Reply
    1. Joe Moorman Post author

      I have seen people put pieces of glass over the tops of mosaics with sharp edges. A local glass shop might be able to cut a circular piece and supply some rubber feet/pads.
      I hope this helps.

      Reply
  12. Lyn

    Do I only need to seal the grout on a glass mosaic lazy susan?
    Does it need to be specifically food safe?
    I’d like to use it as a platter server … Cheeses, dips etc.

    Reply
    1. Joe Moorman Post author

      A tiled and grouted surface isn’t an FDA approved food surface, but it isn’t toxic either. If you want to use it as a serving platter, have your local glass shop cut a piece of glass and put that over the mosaic (with small pads).
      I hope this helps,

      Reply
  13. Karen Kittmer

    Hi,
    I have been advised by a mosaic teacher to seal my mosaic indoor wall hanging with a polyurethane clear sealant. After reading online comments about sealing, I am torn about whether this is a good idea or not. My first project was sealed with rust-oleum clear gloss sealer and the whole thing is very shiny. Can you advise on this? Seal or not? And if so, what product is best. Keep in mind this is indoor art. I understand outdoor is handled differently.

    Reply
    1. Joe Moorman Post author

      This blog article is a complete explanation as to why clear-coat sealers are not a good idea.

      Reply
    1. Joe Moorman Post author

      No coverings, but sealing with a marble enhancer would be the recommended treatment for unpolished tumble-finished marble.

      Reply
  14. Ping

    Hi Joe,

    I realised my black grout on my mosaic piece always left my hand stained even after the finished piece of mosaic art is completely dry after grouting. Pieces sold in the shop with black grout don’t seems to have that issue. Do I need to coat it with something after grouting?
    Appreciate your reply

    Reply
    1. Joe Moorman Post author

      Cured grout should not be leaving any sort of residue on hands. Wash and dry the mosaic and see if you still have a problem.
      Thanks

      Reply
  15. Stephen Carrington

    I did mosaic tiling on the riser part of the steps in my back garden and used Bal superflex wide joint grout for grouting. The grout said indoors/outdoors use, suitable for power showers and swimming pools, frost resistant………..so, I thought it would be the ideal one to use. Three days after i completed the job, we had torrential rain overnight and when I next looked at the mosaic about 2 days later, I noticed a crusty limescale-like film over the surface of all of the ceramic tiles. Is this a substance that came out of the grout or did it come from the stone slabs on the steps? My question is how do i prevent this from happening everytime it rains? One person has recommended using an epoxy based resin over the mosaic and grout on the risers, but I’ve just been told by a technician from Lithofin that might not work . He said i should coat the stone steps and the risers with Stainstop W. Please could you give me your opinion on this.
    Best regards,
    Stephen

    Reply
    1. Joe Moorman Post author

      Hi Stephen,

      It sounds like it was just the normal lime shed by relatively new grout. That problem should stop after a few rains/washes unless the grouts wasn’t mixed with sufficient water or allowed to dry out prematurely before it could properly harden. In that case, no sealing or coating would help.

      Our expertise is in craft and fine art using traditional grouts and mortars, and so we aren’t up on all the different sealing products, but I’m fairly certain that any coating epoxy or otherwise will be prone to the problems described in this article.

      Reply
  16. Carla Cowart

    About 5 years ago I completed large mosaics on my kitchen and living room floors. I used tile adhesive to hold both the broken plates that I clipped into needed shapes and the broken tile pieces I used throughout. I grouted with a charcoal non-sanded grout. Everything has gone very well over these 5 years except that the grout has dulled and small bits are coming up in some places. What can I use to seal the grout so it won’t look dulled after a few years and hopefully it won’t come up? I would like the grout to pop rather than be so bland. Because of the colors I used with the plates I have no problem with those colors popping. Thank you.

    Reply
      1. Carla Cowart

        Thank you so much for the information. Because the kitchen and living is mostly mosaic – approx. 24×15 and most of the grout is sound I think I will take up the unstable grout and then seal it. Trying to find the right sealer is very confusing. The information on the containers aren’t very detailed. So, thank you again for being very precise.

        Reply

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