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There are two types of fresco - wet and dry (secco). Wet fresco ('true' fresco) is a unique technique, where a wall is plastered and painted at the same time. The 'paint' really is thick colored lime...
Line, Shape, Space, Color, Texture, Composition, Light,Tint, Shade, Tone
Those are the basics. From the basics stem the more complex and detailed techniques. [Some examples are: shading, proportions,...