Alla prima (Italian: 'at first attempt') — also called 'wet-on-wet' — is the technique of completing a painting in a single sitting before the underlying paint has dried. It contrasts with the traditional layered approach of painting over dried layers to build depth and complexity. Alla prima became possible as a serious technique in the 17th century, when Frans Hals demonstrated that an entire portrait's vitality and freshness could be captured in a single session. The technique requires absolute confidence — there are no corrections, no second thoughts. The Impressionists adopted it enthusiastically for plein air work, valuing the spontaneity and the way wet paint would blend at the edges of strokes. Modern portrait painters from John Singer Sargent to Lucian Freud have made alla prima their primary method.