The Artist's Handbook of Materials and Techniques (fifth edition) by Ralph Mayer The "Mayer" has been a standard art reference text in America since its first edition in 1940. Mayer covers a stupendous range of issues related to painting and drawing primarily, with compact but insightful chapters or sections on related techniques such as printmaking, etching, lithography, and collage.
Mayer takes the tone of the scholarly craftsman: he has seen what different artists do, describes their procedures, and inserts an occasional clarification based on experimentation or technical research. The main focus is on painting techniques, with a solid section of technical information on individual pigments (including reflectance curves) and a useful section on historical paint names. The watercolorist will learn a lot by reading these chapters carefully, as insights are scattered on almost every page. The discussion of etching, for example, is lucid and evocative: you learn how etchings are done in a way that helps you appreciate these works with a knowing eye.
Minor errors or omissions turn up occasionally, and the seven page chapter on acrylic painting is obviously written without enthusiasm for the medium. Egg tempera gets more discussion, and this is a specific instance of Mayer's evident belief that the old masters had it right and we should all learn the methods that they used.
The main drawback is that the book is text heavy, with no pictures and almost no illustrations. So although art procedures are clearly described, the descriptions may not be sufficient to teach you how to do it yourself.
Nevertheless this is an invaluable and classic text. Mayer asserts that art has historically been a craft based on a very deep technical understanding of materials. His book is a model for artists who aspire to know their tools thoroughly.
Painting Materials: A Short Encyclopaedia by Rutherford Gettens & George Stout This is a compact yet amazingly detailed overview of all aspects of painting by two museum curators with a staggeringly detailed understanding of the materials and tools used in European painting traditions. "Encyclopedia" is exactly the right word for it.
The titles of the six chapters mediums and adhesives, pigments, solvents, supports, tools and equipment, and glossary confirm that there's nothing here about painting technique. You won't find a recipe for watercolor vehicle or egg tempera, or how to do a fresco (for that you have to go to Mayer or Gottsegen). But you will find a detailed discussion of when the various painting techniques appeared, the painters who used them, and their relative strengths and weaknesses. You learn more about the why than the how.
The current edition is a 1966 revised reprint of the original 1942 text. Though some modern materials, such as acrylic binders, find their way into the discussion, most of the modern synthetic organic pigments (apart from phthalo blue, introduced in 1936) are omitted entirely. And the information can get pretty technical drying curves for linseed oil, cross sections of beechwood panels, the solubility and refraction indices of resins. But the expertise, concision and clarity of the book is utterly invaluable to have at hand. Especially for appreciating historical works of art or selecting your own materials, this book is an invaluable help to understand why you're taught to paint the way you do.
The Painter's Handbook by Mark David Gottsegen A solid, up to date and concisely written text that is designed for quick reference on specific topics. As the title indicates, this is a book that does not delve into related techniques such as etching or lithography.
Gottsegen's treatment of materials and methods is somewhere between an encyclopedia and a cookbook. Specific topics, such as papers, tend to be placed as subsections of omnibus chapters; these topical sections are very concise and often focus on defining terms. How-to information on making paints, doing your own lightfastness tests, or preparing a wall for a mural are laid out in cookbook style: list of ingredients first, then step-by-step instructions. There is never any mention of higher purposes, so that a reader without any awareness of art might conclude it is an activity similar to home repair.
Gottsegen appears to be the most up to date handbook available for painters, but his focus solely on current materials and their physical manipulation with a heavy dose of documentation on the ASTM testing standards left me wanting a better historical background and integration of the materials into their artistic purposes.