After discussing the difficulties associated with finding and interpreting artists' correspondence as a source of information on their oil painting techniques, this study evaluates the authority, relevance, and accuracy of instruction manuals, handbooks, or reference manuals on materials that describe the sources and manufacture of mediums, varnish ingredients, and pigments, and various kinds of compendiums of the arts. Questions whether this literature was influential or offered an accurate reflection of the use of materials and practices of British 19th-century painters. The information collected here has been entered in a computer database and will be made available to conservation and art history research.