Miniature Mosaic: Mountain Valley Twilight

I continue to work on a series of miniature mosaics mounted on what I call my “mortar stones,” which are irregularly-shaped backers made by spreading thinset mortar on 3 or 4 layers of hardware cloth (steel mesh).

My latest in the series is my mosaic Mountain Valley Twilight, which is 9 x 6 x 1/2 inches and made from our American-made stained glass and black non-sanded grout.

Indirect Method

Here is the photo of the mosaic after the tile was laid out over a pattern and picked up with Mosaic Mounting Tape.


There was clear contact paper taped over the pattern with the sticky side up, which keeps the tiles from sliding out of position as they are arranged

This temporary surface of sticky contact paper allows you to arrange tile by trial and error before glue is involved.

The Mosaic Mouting Tape has a stronger adhesive than contact paper, and so it easily lifts the whole mosaic off the temporary surface.

Or at least that is the case when you are using whole uncut tiles.

When your mosaic is made from smaller pieces of glass, the Mosaic Mounting Tape might not securely grip every little piece.

For this reason, it is safer to flip the whole thing over and carefully peel the contact paper from the bottom of the mosaic while it sits face-down on the Mosaic Mounting Tape.


Mounting the Mosaic

Mounting the mosaic was done by spreading about 3/16 inch of thinset mortar on the backer, and then placing the backer on the back of the mosaic while it sits facedown on Mosaic Mounting Tape.

Then the mosaic is flipped face up as shown in the photo above, and tape is rubbed and pressed so that the mortar presses up between the tiles.

The goal of rubbing and pressing the mosaic is to make sure that each tile is embedded in the mortar and

The goal is not to completely fill the grout gaps with mortar, but that happens in places. It’s unavoidable if the mosaic is rubbed and pressed into the mortar sufficiently.

If I don’t see mortar pressing all the way up to the Mosaic Mounting Tape at the tops of the gaps in some places, I can be sure there will be some place in the mosaic where I didn’t rub sufficiently to seat all tiles.


Cleaning Grout Gaps

Before a mosaic can be grouted, any mortar that fills the grout gaps needs to be cleaned out using tools such as dental picks, boxcutter blades, embroidery needles, or some other small metal stylus.

Care must be taken to avoid chipping and flaking the faces of the tiles, which can easily happen if the metal stylus is forced or twisted in tight cracks between tiles.

Before grouting, I also filed away excess backer in places where it extended more than 1/4 inch beyond the edge of the mosaic. For this shaping process, I used a Diamond-Grit File.

Non-sanded Grout

The grout gap was only an incidental gap, meaning whatever tiny irregular cracks that remain after positioning the glass pieces together as tightly as possible. For this reason, the grout I used was non-sanded.

Grout Color

For grout color, I used black as always.

Consider the photo above of the mosaic before grouting. Notice how the light-colored mortar shows in the cracks between the tiles, giving us some idea what the mosaic would look like with a light or medium gray.

I think mosaics look better when those tiny cracks are black, like most cracks in real life.

The black grout line also resembles the lead-channel seams in a stained-glass window.






2 responses to “Miniature Mosaic: Mountain Valley Twilight”

  1. Annette Avatar

    I was wondering if you could use contact paper with the tiles face down. Then add adhesive and not thinset on the backer. Turn the backer around and place on top of the tiles that are facing down on the contact paper. When dry, peel the contact paper off and then grout.

    I’m not sure when to use a glue adhesive and when to use thinset. Is it glue for inside and thinset for outside projects?

    1. Joe Moorman Avatar
      Joe Moorman

      Hi Annette,

      That is correct: Weldbond or another HIGH-quality PVA adhesive is used for dry indoor mosaics, but thinset mortar is required for outdoor and wet mosaics.

      The method you describe is one that I have used many times. It’s good if you don’t mind looking at the design reversed and upside down while you work.

      If you want to look at the mosaic as it will be, then you can work right-side-up and then pick the mosaic up with Mosaic Mounting Tape.

      I prefer Weldbond adhesive over thinset mortar when there are many tiny pieces of glass, which is common for small fine-art/icon mosaics.

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