Can I Use Silicone Caulk as a Mosaic Adhesive?

First I want to clarify that I am not talking about the invisible pore sealers that are used to seal tile and grout. Those are silicone-based as well, but my post about mosaic birdhouses was talking about using silicone caulks and sealing gels as an adhesive for mounting tile. I have serious doubts about these.

glass-on-glass stained glass mosaic

Glass-on-glass mosaics such as this sun catcher use silicone to adhere stained glass pieces to a clear glass backing. However, for any other style of mosaic art, silicone should be avoided.

I have seen some silicone adhesives used on tile sample boards that was so strong that it was impossible to pry off a tile without breaking it, but the tile did come off in pieces. However, with fully cured thinset mortar or Weldbond (white PVA adhesive), the tiles sometimes have to be chiseled off into a powder in order to repair a mosaic.

This may seem like a meaningless distinction if the silicone is strong enough, but over time the difference in strength will show itself in missing tiles.

Also, how well does the silicone product age? Does it become brittle? What else is in it? Will the flexibility of the silicone gel or caulk allow the tile to move and crack up the grout over time? Will it be like the old caulk or old silicone gel on a piece of window glass, capable of being scraped off fairly cleanly?

CLARIFICATION

I’ve done some follow up research, and learned a couple of things. First, a silicone adhesive or caulk may be a good option for people making mosaic mannequins or mosaics on plastic or fiberglass sculptures. Note that I haven’t evaluated this myself.

Another thing that I have learned is that a silicone-based caulk should not get brittle in ultraviolet light or cold temperatures in the same way that acrylic-based caulks will. Silicone is also waterproof.

However, the flexibility of silicone-based products when fully cured is still a problem in my opinion for mounting architectural mosaics. If the grout is to remain intact (and thus protect the substrate from water damage), then the tiles cannot be moving slightly every time pressure is applied to the surface of the mosaic.

7 thoughts on “Can I Use Silicone Caulk as a Mosaic Adhesive?

  1. Nico Morris

    Silicone sucks as a tile adhesive for three important reasons

    I NOTHING will ever stick to a surface once contaminated by silicone,not even silicone!

    (they sell a solvent for it now,but it costs as much as the new product,and needs a double application to work YUK , silicone on wood,or old aluminum(such as trailers,or paint,will eventually move so much, water gets under it expands and contracts with heat..
    it will stick to your tile for centuries ,and getting it off,short of re firing the tile,is near impossible YUK it is a flexible inflexible product good for making aquariums from brand new glass PERIOD (all that being said I have a fiend who loves it see his work Dickens 44 bascom (origination of recycadelic mosaic ).
    Polyurethane is STRONG and flxible ,waterproof and can be colored with oil paint. Epoxy is cool for indoors but shrinks in 20 years if exposed to uv continuously.. can break substrate..and tiles. also can be colored with oil paint my favorite is acrylic, and good ol thinset.. cement for brittle strong stone, acrilic for junk and weird substrates or Silicone for things like flexible marble towers!

    Reply
  2. Jane

    What about silicone to apply glass tiles to fiberglass statues??? Using silicone grout??
    I am desperately looking for a bond that will last outdoors but will not weigh as much as mortar/concrete.
    They use silicone in fiberglass swimming pools…
    Please help!

    Reply
  3. Patricia Lane

    I did a ceramic mosaic on mesh then used a cement glue to stick it on a plastic table. The whole thing can now be lifted off. Will silicon work?

    Reply
    1. Joe Moorman Post author

      Hi Patricia,

      It might. You can test the silicone by applying some and allowing it to harden and the scraping it off. You can improve bonding by scuffing the table with coarse-grit sandpaper. A better approach would be to glue the mosaic to a table top made from cement backer board or foam-core tile backer board. Plastic isn’t a good surface for mosaic because it flexes, and as you have seen, it doesn’t bond well to mosaic adhesives and grout.

      I hope this helps!
      Joe

      Reply
  4. Jane

    I’ve used silicone glue for outdoor projects.ButI recently read that you can’t use grout over it??
    Not even silicone or epoxy grout?
    So the only option is thin set? I use very small pieces and a lot of detail do thin set is difficult.
    But if no type of grout sticks to silicone I guess it’s no longer an option?

    Reply
    1. Joe Moorman Post author

      Hi Jane,

      Even if you got the Silicone on the bottom of the grout gap, the grout could still stick to the sides of the tiles. People do glass-on-glass mosaics all the time with silicone and still grout with traditional grout. Keep grout gaps smaller to make it less of an issue.

      Reply

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