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Outdoor mosaics: four principles for successful work

Outdoor mosaics: four principles for successful work

How to make outdoor mosaics that last

Mosaic of a leopard and plant
Leopard mosaic, Hackney Downs Mosaic by the Hackney Mosaic Project

Mosaics are defiant in their making and profoundly human. There is something verging on the insane about placing countless pieces of things next to each other to create something new and whole. If not insane, then at least belonging to a different era. Nowadays we do things fast and virtually. Mosaics are too tactile, too slow and in a funny way too permanent for our 21st century hyper-mobile way of living.

Photo of an outdoor mosaic on a wall with rosesOutdoor mosaics add an extra layer of not-quite-belonging to the art form. In addition to the absurd amount of time they take to make they are also a declaration of temporal optimism. They are not just a squandering of resources (why not just buy some pretty tiles or employ a mural painter?) but they announce that they are here to stay despite whatever the elements can throw at them. Every mosaic, whether it wants to or not, quietly refers to its ancient predecessors. They have been around for thousands of years, so there is a chance that this mosaic will be too.

Mosaic of a stalk and leaves

The trick, however, is to make sure that that declaration does not ring false. When making mosaics for outdoors it is important to pay attention to four fundamental principles so that your mosaics will, quite literally, stick around.



Outdoor mosaics 101

  1. Materials

Check your materials are suitable for outdoors. I know it sounds obvious but things can slip in that aren’t suitable for certain weather conditions. Lots of things will work just fine: stone, shells, plastics, Winckelmans unglazed ceramic and glass, both vitreous and smalti. But what about crockery? Well, it depends. China that is printed – that has had a design transferred onto it in a similar way to applying a sticker, is not going to fare well under repeated freeze-thaw conditions. It won’t be long before the transferred design will crack and simply peel off. Bone china, on the other hand, will last.  How do you tell? Check the stamp on the bottom of the cup/plate and it will say ‘bone china’.

Substrates for outdoor mosaics2. Substrates

Not all substrates are created equal. Wediboard/Jackoboard, a compressed foam board used to line bathrooms, is a superb choice for outdoor mosaics. It is lightweight, it’s easy to apply hanging fittings and it has a concrete skim over the surface which protects it from the elements. Slate and concrete forms (pictured left) are also great for outdoor mosaics. However, terracotta and wooden bases are more problematic. Terracotta pots are sold in plant nurseries with the clear implication that they will be suitable for outdoors but some crumble away after a few winters while others are robust whatever the weather throws at them, so choose with care. Wood is best avoided outdoors. Water is likely to permeate even sealed and treated wood over time so try to find a suitable alternative.

Photo of tile adhesive packaging used for outdoor mosaics3. ADHESIVES

Getting the right adhesive for your outdoor project is imperative. For outdoor mosaics you need to use either a strong outdoor glue (like Titebond II Premium Wood Glue) or tile adhesive /thin set that is specially manufactured for outdoor use. There are a number of different tile adhesives/thinset options on the market – just make sure that the packaging says it is for exterior use. Also, be sure to follow the instructions about how and when to apply the adhesive. For example, the Mapei adhesive pictured right can only be used when the surface to which the mosaic is being applied is above 5 degrees centigrade both at the time of setting and for two weeks afterwards. PVA is not recommended for outdoors.

Cross section view of a Byzantine pebble mosaic4. Thickness of adhesive

When using tile adhesive you want to make sure that the adhesive covers half to two-thirds of your tesserae. In other words, half to two-thirds of the thickness of each tessera is embedded into the adhesive bed. Not making a thick enough bed is often the reason that outdoor mosaics don’t last. This is where the early mosaic makers really knew what they were doing as you can see from this cross section of a Byzantine era pebble mosaic. I’ve made a YouTube video about making outdoor mosaics and if you watch from the 9:55 point you will see this principle applied in practice.



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