Two wall cross-sections, each with a wall, a base plaster and a top plaster. In buon fresco the pigment sits in the top of the wet plaster and is locked in as it sets with carbon dioxide from the air. In secco the paint sits on dry plaster and a piece is shown flaking off.

Concept · Paint and Its Surface

Fresco

In fresco the painter works on lime plaster while it is still wet; as it sets, the color becomes part of the wall.

Follow the arrows: carbon dioxide from the air turns the lime back into a kind of stone, with the color inside it. Paint added once the plaster has dried, called secco, rests on the surface and may flake off.

  • Each day's patch of fresh plaster, a giornata, was only as big as the painter could finish before it dried.
  • Not every color suits wet lime: Pliny says indigo does not.

See

Image: Made for this site · Original work

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