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These DIY instructions are based on my mosaic-making expertise (such as it is). They're intended for home crafters who probably don't have access to workshop space, fancy powertools, etc.

Cleaning up glass shards

Large shards or fragments of glass can be swept up using a small hand broom.

 

The best way to clear small shards or fragments is to wipe the surface off with several layers of damp paper towels.

Cutting Cement Backer Board

I use cement backer, such as Hardie® Backer Board, for all of my coasters and most pieces smaller than about 8" x 8". Once you get the hang of it, cutting backer board is relatively easy at home. Below are instructions for the score and snap method.

Materials

  1. Cement Backer Board, such as Hardie® Backer Board
  2. Carbide-tipped Scoring Blade
  3. Tape measure or ruler
  4. Pencil
  5. Scrap towel and/or cardboard

Steps

  • Gather and lay out materials. To avoid denting or chipping your work surface, lay down a layer or two of scrap cardboard and/or rags.
  • Mark where you want to cut. When using this method, straight cuts work best. Don't forget to measure twice and draw once!

  • Using a ruler or other straight implement as a guide, score where you want to cut using a scoring blade. To make accurate scores, use a decent amount of pressure and don't try to move the blade too fast. After the first score, you likely won't need to use a ruler to guide the blade, it should glide along the existing scores.

  • Continue to score until you've reached about a third of the way through the backing board. There is no need to score all the way, or even most of the way through the board.

  • Place the backing board on the edge of your work surface with the score facing up. With one hand, hold the board to the work surface. Quickly break off the desired piece by quickly snapping downward.

  • If your work surface has rounded corners, or you're working with large sections of backer board, it can be easier to snap pieces off on the ground. In this case, place the score facing down, and snap upwards.

Mortar vs. Grout

What type of grout should I use?

There's two types of grout you'll likely end up dealing with as a mosaic artist: sanded and unsanded grout. Both types can be purchased at your local home improvement store, since they're the same types of grout you'd use if you were tiling your bathroom or kitchen. In my experience, the decision of which to use comes down to the size of the gap left between the tiles and whether or not the mosaic will be exposed to the elements (e.g. water).

 

Generally, follow these rules-of-thumb to decide which to use:

  • Sanded: for larger gaps between tiles and for pieces that won't be exposed to much water
  • Unsanded: for smaller gaps between tiles and pieces that will be exposed to water

 

For example, I now only use unsanded grout for coasters since that results in a piece that's more resilient to constant spills and wiping. For larger wall pieces, sanded usually works well. However you MUST pay attention to the spacing between the tiles. If you've placed tiles closer together than about 1/8", you'll need to use unsanded grout. Sanded grout will have difficulty filling in the spaces.

How to use unsanded grout

Note: the particular proportions of water/grout/etc. may vary depending on the brand of grout, the ambient humidity, and more. As always, practice makes perfect when it comes to knowing what consistency wet grout ought to be!

 

  • I'm currently using Polyblend Non-Sanded Grout

 

Steps

  1. A FULL 24 HOURS after finishing gluing, prepare your materials.
    • Mosaic to grout
    • Bin/container/bowl/recepticle for grout mixture (e.g. I use old take-out containers, which can be reused many times)
    • Stirring implement (e.g. plastic spoon or similar)
    • Water
    • Scale (optional but very handy)
    • Paper towels
    • PPE (gloves and mask)
    • Newspaper/cardboard/surface coverings
  2. Mix grout and water.
    • Wear a mask while working with dry grout!
    • In case it isn't obvious, unless you're grouting something truly HUGE, you do not need to use a whole box of grout. 
    • Once wetted and dried, grout cannot be reconstituted. So don't make a big batch thinking you'll use it up next time.
    • For Polyblend Non-Sanded Grout, this is the correct proportion: Weight Water * 3.24 = Weight Grout
    • Mix the water and grout together thoroughly to make a stiff paste then let sit for 3-5 minutes.

Example grout and water weights. Here, I'm mixing white and black grout together to make gray. Make sure to mix the grout powders together extrememly thoroughly before adding water.

  1. Smear grout onto your mosaic using a gloved hand, plastic utensil, or palette knife.
    • Get as thorough and thick a coverage as you can.
    • You want to make sure to get grout into each crack, crevice, and gap.
  2. Start pushing grout into the gaps.
    • Small scraps of paper towel are useful here rather than stiff tools.
    • This is also the time to start removing excess grout in small amounts.
    • Unsanded grout is sometimes a bit like plastic wrap: it sticks to everything except what you want it to and often to itself. 

 

  1. Oh no! A tile popped off!
    • It happens to the best of us. Don't panic and remember: grout is filler not glue.
    • Take the tile all the way out. If grout fills the gap, gently scoop it out. Glue the tile back in place and gently heap oodles of grout over it.
    • Keep working on the rest of the mosaic, and come back to the piece later.

 

  1. Let the grout dry for a few minutes.
    • The length of time will vary depending on the temperature and humidity, but ~10-15 minutes usually works.
    • For large pieces, I find working in increments eliminates the need to simply step away for this time: perform steps 2-5 on portions of the piece, then go back to the beginning and continue.
  2. Keep pushing grout into gaps and wiping off the excess with paper towels.
    • If you had to glue pieces back in, avoid those areas for as long as you can.
  3. Once most of the excess grout is removed and the gaps are filled, clear the "haze" from the tiles
    • If the grout has started to dry, use slightly (SLIGHTLY) damp paper towels.
    • Once fully dry, the haze is impossible to remove completely, so don't skip this step.
  1. Finish with a polish with a lint-free cloth.
    • At this point, nothing should have grout that you don't want to permanently have grout: gaps, tiles, etc.
  2. Wait a full 24 hours before sealing with a grout and tile sealant.