Gouache is both a technique and a product. The technique, dating back to before the
renaissance, refers to the use of white to achieve opacity in water based colours.
Opaque techniques were popularised by the Impressionists and Post-Impressionists,
in their use of pastel, lithography and wood cuts.
Gouache, the product, was a result of this interest in both opaque and water based products.
Poster color appeared after the first world war and this was significantly improved upon with the
introduction of DesignersÆ Opaque Water Color in the 1930Æs.