Alla prima

Wet-on-wet, or alla prima (Italian, meaning at first attempt), is a painting technique, used mostly in oil painting, in which layers of wet paint are applied to previously administered layers of wet paint. This technique requires a fast way of working, because the work has to be finished before the first layers have dried. It may also be referred to as direct painting or the French term au premier coup (at first stroke).

Traditionally, a new layer of oil-based paint is applied to most parts of a painting only after allowing a previous layer to dry completely; this drying process can take from several days to several weeks, depending on the thickness of the paint. In contrast, work performed using "alla prima" can be carried out in one or more sessions (depending on the types of paint used and their respective drying times), and it is common for such a work to be finished in only one session or "sitting".

In the medium of watercolors, wet-on-wet painting requires a certain finesse in embracing unpredictability. Highly translucent and prone to accidents, watercolor paint will bloom in unpredictable ways that, depending on the artist's frame of mind, can be a boon or a burden.

Wet-on-wet painting has been practiced alongside other techniques since the invention of oil painting, and was used by several of the major Early Netherlandish painters in parts of their pictures, such as Jan van Eyck in the Arnolfini portrait, and Rogier van der Weyden. Among the many Baroque painters who favored an alla prima technique were Diego Velázquez and Frans Hals. In the Rococo era, connoisseurs appreciated bold alla prima painting, as exemplified in the works of artists such as Jean-Honoré Fragonard, Francesco Guardi, and Thomas Gainsborough.

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