There are two methods of gaining access to bygone technologies used in art: to study literary sources and to evaluate the results from scientific examination of the objects of art. The findings of scientific examination can help interpret old art technological terminology. A good deal of printed technical literature, as well as published archive material (bills, contracts, etc.) about individual works of art are available as sources about 18th century South German decorative painting. Besides German originals there are an increasing number of tranlations from French, Italian and English in the second half of the century. With the establishment of technology as a science (at the University of Goettingen in 1772) the literature on painting techniques becomes more precise and more practicable. Archival sources of individual works of art can be compared to findings of scientific examination. The philological problems of the old painting terminology, which sometimes differs from the language in the printed literature, have not yet been examined. possible changes in meaning of certain 18th century terms that were already used in the late Middle Ages dialect forms must still be checked. Examples of techniques of applying leaf-metal and such cases where historical literary sources and scientific data are available for the same work of art demonstrate this difficulty.