This is my step by step explanation (for anybody who might find it useful!) of how I made a mosaic on a building block for placing into an existing garden wall:
1. Source a breeze block that can be easily fitted into your garden wall.
2. Draw out guidelines for the design on a piece of brown craft paper, within a rectangle the size of the block. Tape it down to a suitable piece of board. In my case, I was recreating the same fish mosaic that I’d made before on cement board because the client had seen it and commissioned one for her garden wall, so I had a photo of my previous mosaic to work from.
drawing on brown paper taped to board
3. Begin making the mosaic upside down on the paper, sticking the tesserae down with a soluble adhesive. Some mosaic artists use PVA, but I prefer to use wallpaper paste, as in my experience it works better for this process.
working on the background
4. Once complete, use a craft knife to cut the mosaic out from the surplus brown paper. Check that it fits the block!
5. Prepare the block by sealing the surface with a coat of diluted PVA (approximately 1 part PVA to 5 parts water).
6. Mix the grout that you have chosen. For this project, I’ve used a light grey (BAL wide joint)
pre-grouting the mosaic
7. Pre-grout the mosaic so that the gaps between the tesserae (interstices) are filled. Remove grout from the tesserae by carefully wiping it away with a well wrung damp cloth.
carefully remove grout from surfaces of tesserae
8. Now mix the adhesive. This should be a cementitious tile adhesive. Apply the adhesive to the prepared surface of the block as evenly as possible and rake with a notched trowel.
9. Lift the mosaic, still on the brown paper, and hover it over the block, (paper side up!!) When you are in the correct position, lower it gently into place.
10. Pat down over the brown paper firmly with a grouting trowel. (I think it is useful to put a flat board over the mosaic and tamp down over the board, as this helps to ensure a flush finished surface) Allow the adhesive to set.
sponging the brown paper prior to peeling off
11. Sponge off the brown paper. Allow water to thoroughly soak into the paper for quite a few minutes before carefully peeling it away.
12. Re-grout the mosaic, clean off and allow to set. Grind away any rough edges and then seal the surface with a stone sealant. The mosaic block is ready to be fitted into your garden wall.
As you might have noticed, I didn’t remember to photograph every stage but I hope that this is still a helpful guide. I will post a photo of it in situ once it has been fitted into the garden wall as soon as possible…………….
and here it is ready to be fitted into place