HALF-GROUT — A layer of cement-based tile adhesive or cement/sand mix laid over the base to a depth of around 5mm – it will vary depending of the thickness of the tesserae – into which the tessarae can be pushed if they are not suited to grouting in the standard way.
HARDIBOARD — Cement-based backerboard manufactured by the James Hardie® company and available in 6mm and 12mm thicknesses.
HARDIE — A tool with a steel or iron cutting edge, rather like a stonemason's chisel; the hardie is fixed into a log and used together with the mosaic hammer to cut tesserae.
HELLENISTIC TECHNIQUE — The mosaic techniques developed in the Hellenistic period, that is, between the death of Alexander the Great in 323 BC and the Battle of Actium in 31 BC.
Hispano-Moresque — A term used for pottery and tiles produced in Spain (in places such as Malaga and Valencia) during the 14th and 15th centuries under Moorish influence. It is characterized by the use of lustre often combined with cobalt blue on a white tin glaze.
HYDRAULIC LIME — Hydraulic lime is produced by baking and slaking limestone and clay. When mixed with sand, it is used for plaster coats and interior foundations. Lime is used in traditional buildings.
HYDROCHLORIC ACID / muriatic acid — A powerful acid, an aqueous solution of hydrogen chloride, used as a cleaning agent to remove unwanted cement and cement–based products from the surface of a tile or a mosaic.
