The intonaco is the top layer of plaster in a fresco. The intonaco is the layer that is applied in sections called giornate(a) and can be painted on either wet or dry.
When attaching small portions of the intonaco, restorers used a watery emulsion called CEF 10 Wacker. CEF 10 Wacker s a dispersion in very fine particles on the basis of a trypolimer of ethylene, vinylacetate and vinyl chloride. Larger pieces of intonaco are attached using Ledan TB1 CTS, which is a mortar composed of binders such as cement and hydrated lime, of inert substances, such as slate and quartz, and of fluidifying additives, retarders, and aerating and antisedimental agents. What both of these do is recreated an extremely thin layer of plaster like material that hardens and chemically binds the underlayer (called the arriccio) and the detached intonaco.