SMALTO — Smalto (plural - smalti) refers to opaque, coloured glass tesserae.

These smalti are created by fusing a mixture of vitrifying and stabilising substances, flux, and other additives at temperatures ranging from 1200°C to 1400°C. The molten glass is poured into flat slabs, which are subsequently broken into individual smalti pieces with rough and irregular surfaces.

For the inclusion of gold tesserae, a thin layer of gold leaf can be embedded within the smalti. Originally developed for Byzantine mosaicists, smalti contains metal oxides that offer a vast array of colour possibilities.