It can be inferred from the passage that gouache paints ……….. .

Painting is the application of some coloured pigment to a surface and has developed into an expressive art form. The most common types of paints used today are oil paints and water colours. Most oil painting is done on a prepared canvas or wooden board. Oil paints take several days to dry, which allows the artist to work and rework on the canvas or other surface in the meantime. Water colour painting requires a totally different technique. As the name implies, water is the fluid mixed with the pigments, while paper is the only surface suitable for the paints. Because the water dries quickly into the paper, the work itself has to be done quickly, and it is difficult to correct mistakes. Gouache paints are also water-soluble, but stronger in colour and tone than true water colours.