Mosaic has been used as surface decoration for buildings and other outdoor environments for centuries. Creating mosaic for exterior locations presents a new set of challenges as the weather conditions can greatly affect their longevity. Tiles that work in sunny Florida may not last in Wisconsin where we experience extreme variations in temperature and extended freeze/thaw cycles.
The most important aspect of making mosaics to be sited outdoors is to be sure that the materials you plan to use can withstand your weather conditions. Mosaics take a lot of time, and you are guaranteed success if you keep in mind the marriage of appropriate substrate, adhesive and mosaic materials (tiles, glass, etc.).
You can mix different materials, but be sure each is rated for your climate. It is essential your substrate is clean and in some cases will benefit from a scratch coat of mortar or specialty primer. The appropriate adhesive for most exterior mosaics is thinset mortar. There are a few exceptions, but they are rare and those alternatives include an epoxy-based adhesive or silicone and or rubber adhesive. All adhesives for exterior mosaics are in the “construction trade” world. You would NEVER use PVA glue outside (it is water-soluble).
