The watercolors are obtained by agglutination of dry powdered pigments mixed with gum arabic, which is extracted from the acacia and which solidifies by evaporation, but which is soluble in water. The watercolors, in solid state, dissolve in water and are applied to the paper with a brush. Although watercolor is a relatively modern type of painting, different water-based paints have been used throughout history. It can be considered that the first watercolors are the papyri of ancient Egypt, and the early Oriental drawings in ink are a monochrome watercolor form. In Medieval Europe, water-soluble pigments bound with an egg-derived densifier were used for miniature manuscripts; in the same way, the medieval frescoes were painted with pigments mixed with water thickened with opaque white paint. Subsequently, other types of opaque water-soluble paints emerged, very close to watercolors, such as gouache, which is still used today.