Fresco - The Intonaco

Fresco colors will hold only if they are applied to the intonaco while it is fresh. Once the lime crust forms on the intonaco, all painting must cease. Therefore the size of the area over which the artist lays the intonaco must be limited by the amount of painting that can be finished before the plaster begins to dry solidly. It is usual to work in sections, starting at the top of the wall, to avoid spattering finished work.

The sand finish on the section of the wall to be painted is wet thoroughly several times. After a brief wait for the water to be absorbed into the plaster, the wall is ready to receive the intonaco. As in the preceding coats, the intonaco mortar may be applied in two or even three very thin layers, their total not to exceed 1/5".

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1. The very thin skim coat is laid on and scoured with the float to cut into the lime crust of the sand-finish coat. The upper coat of intonaco must be laid on before the skim coat has hardened completely.

2. The mortar is surfaced like the sand finish with a float. It may be smoothed still more by means of a metal smoothing trowel if the artist desires a highly polished surface. After the area has been surfaced, it is ready for the painting.