Answer: — It lets viewers know that (insert artist's name here) painted that painting. It helps us artists to have a cohesive body of work. That doesn't mean though that your technique must stay the same your whole life.

Explanation: The five main painting mediums used in the book are acrylics, watercolors, oils, pastels and tempera. The lessons in the book show you how to use these various painting media in combination with each other, and also with other materials, such as wax, gels, powders, gelatin, conte and more.