Free technical guides for artists

Both Winsor&Newton and Reeves have free downloadable pdf guides to various materials and techniques. These are available at the links below. Obviously these heavily emphasize their products but the information is still useful and can be applied to other brands.

http://www.winsornewton.com/resource-centre/the-oil-colour-book

http://www.reeves-art.com/guides-and-tips


This is a guide to historical painting techniques, materials and studio practice from The Getty Conservation Institute, http://www.getty.edu/conservation/index.html.  Although the guide is done through the prism of conservation, that requires a considerable understanding of the original process involved, which is well explained. They have many other documents available.
 
http://www.getty.edu/conservation/publications_resources/pdf_publications/historical_paintings.html