Did you wonder how Pompeians did those deep seamless backgrounds of their frescoes? It was not that complicated - a thin coat of colored lime putty was trowelled over fresh Intonaco creating mottled look of the sky...
 

The "Pompeian Sky" background for the first giornata of the Dolphin Fresco is ready - now it is the time for the painter to transfer the cartoon and complete the giornata (painting day) with the rest of the composition. There is no time to waste - highly polished intonaco is a very temperamental surface to work on as well as it would allow for shorter working time...