Drawing Techniques: a Guide
Dry Media: Fabricated Chalk and Pastels  
Ochres, yellows, browns and other natural colored chalks were available by the sixteenth century. Early in the century Milanese artists like Bernardo Luini, following Leonardo's example, were using them for flesh tones and for details. Jacopo Bassano and Federico Barocci of Urbino developed a sophisticated technique of combining them, blurring the contours by rubbing the chalk with the finger or a leather stump. By the eighteenth century French artists had formalized the medium for highly finished portraits which duplicated in their own way the effect of finished oils.  
Black, Red, and White Chalks