PREFACE
This was not started as a book. It was begun as a series of notes
and was published as separate sections in Technical Studies in the
Field of the Fine Arts from 1936 until 1941. At the start those data
were assembled about which little information was available, par-
ticularly those on supports and mediums. As more were put together
and a book was suggested, a question came up about discarding the
sectional arrangement and putting all of the entries in a single alpha-
betical sequence. In the end it was decided to keep the five sections
intact and to print them as they are. The grouping is, perhaps,
slightly awkward and is certainly unusual in any volume that calls
itself an 'encyclopaedia/ but that word seems open to some variety
of definition, and practically there appeared to be good reasons for
leaving the data arranged as they were.
Chief among those reasons is that custom has made such an
arrangement habitual. Painters and all workers in the materials of
paint have grown familiar with handbooks and texts in which pig-
ments, mediums, and the others are treated separately. Individual
names are apt to be unknown and information about a general kind
of material can probably be got more handily when that kind is
segregated. Time and trial will show whether or not a change might
have been better and whether or not it should be considered at some
later date.
Those who have occasion to use this book will find it uneven as
to quantities of information set down. That is because so much study
has been made of certain kinds, and so little of others. Pigments, for
example, have been explored by painters since the beginning of the
art and by scientists for many generations. Solvents, on the contrary,
are most of them new things, recent developments in industry and in
the painting trade. Their utility is limited and knowledge about them
is only beginning to work its way into the arts. The section on tools
and equipment has only a small amount of previously published
reference data. Much of it, in contrast to other sections, is assembled
directly from sources. Headings or titles of the sections may need
some explanation. The word, support, as defined in a publication on
museum records by a committee of the American Association of
Museums (Technical Studies, III [1935], p* 204) means 'the physical
structure which holds or carries the ground or paint film/ This would