Editing Fresco (section)

==Other types of wall painting==
[[File:Giotto di Bondone - No. 18 Scenes from the Life of Christ - 2. Adoration of the Magi - WGA09195.jpg|thumb|Fresco by [[Giotto]], [[Scrovegni Chapel]] in Padua. Sky and blue mantle of Maria were painted ''a secco'', and large part of the painting is now lost]]

A [[fresco-secco|secco or fresco-secco]] painting is done on dry plaster (''secco'' meaning "dry" in Italian).  The pigments thus require a binding medium, such as [[egg (food)|egg]] ([[tempera]]), glue or [[oil painting|oil]] to attach the pigment to the wall.  It is important to distinguish between ''a secco'' work done '''on top''' of ''buon fresco'', which according to most authorities was in fact standard from the Middle Ages onwards, and work done entirely ''a secco'' on a blank wall.  Generally, ''buon fresco'' works are more durable than any ''a secco'' work added on top of them, because ''a secco'' work lasts better with a roughened plaster surface, whilst true fresco should have a smooth one.  The additional ''a secco'' work would be done to make changes, and sometimes to add small details, but also because not all colours can be achieved in true fresco, because only some pigments work chemically in the very [[alkaline]] environment of fresh lime-based plaster.  Blue was a particular problem, and skies and blue robes were often added ''a secco'', because neither [[azurite]] blue nor [[lapis lazuli]], the only two blue pigments then available, works well in wet fresco.<ref>All this section - Ugo Procacci, in ''Frescoes from Florence'', pp. 15–25 1969, Arts Council, London.</ref>

It has also become increasingly clear, thanks to modern analytical techniques, that even in the early Italian Renaissance painters quite frequently employed ''a secco'' techniques so as to allow the use of a broader range of pigments.  In most early examples this work has now entirely vanished, but a whole painting done ''a secco'' on a surface roughened to give a key for the paint may survive very well, although damp is more threatening to it than to ''buon fresco''.

A third type called a ''mezzo-fresco'' is painted on nearly dry intonaco—firm enough not to take a thumb-print, says the sixteenth-century author Ignazio Pozzo—so that the pigment only penetrates slightly into the plaster. By the end of the sixteenth century this had largely displaced ''buon fresco'', and was used by painters such as [[Giovanni Battista Tiepolo]] or [[Michelangelo]].  This technique had, in reduced form, the advantages of ''a secco'' work.

The three key advantages of work done entirely ''a secco'' were that it was quicker, mistakes could be corrected, and the colours varied less from when applied to when fully dry—in wet fresco there was a considerable change.

For wholly ''a secco'' work, the intonaco is laid with a rougher finish, allowed to dry completely and then usually given a key by rubbing with sand. The painter then proceeds much as he or she would on a canvas or wood panel.