Mosaics made with the direct method involve gluing tesserae face up on to a firm base allowing the pattern/picture to emerge as it will finally appear. Once completed the mosaic is then grouted and any excess grout removed once dry. This is ideal for small pieces of art work, however, it is difficult to keep an even surface level if using varying depths of tesserae.
In the indirect method tesserae are glued face down on a temporary supporting medium. Once completed the entire mosaic is turned over and fixed in its final position. The initial support is then removed. If required the mosaic can then be grouted and cleaned up as above. This is a useful method for creating larger art works such as those made up in sections away from the eventual site of installation.
Mosaic Artist (UK based)