286 PAINTING MATERIALS

pencils. Their use goes back to the earliest antiquity of the art, and they were very
common during the Renaissance. Cennino Cennini (C. XXXIIII, Thompson, p.
20) speaks of a certain black stone from Piedmont soft enough to be sharpened
with a penknife, very black, and good for drawing. Meder (p. 122) says that
Leonardo da Vinci was the first to use chalk throughout for a complete and
finished drawing.

FIGURE 6. Equipment for use with painters' canvas. At a is shown a corner section of the
common stretching frame. These pieqes, made so that they can fit together to a mortised
and mitred corner, form a complete frame by a combination of four and are sold as
single pieces of various lengths by artists' colormen. They are usually of pine and are
about 1X3 inches in section. At I is a type of pincer or plier used for stretching canvas
over such a frame. The fabric is gripped between the two broad jaws and the spur be-
neath serves as a fulcrum, acting against the edge of the stretcher frame.

Channel Edge Support. This name is given arbitrarily to a wooden channel
occasionally seen attached to the end grain edges of thin panels in paintings of
the studios particularly of Dutch artists of the XVII century. One is found in a
work attributed to Rembrandt, 'The Painter in his Studio/ formerly in a private
collection in England (Burlington Magazine, CCCLXXII [1925], p. 264). This
channel was undoubtedly fitted without nails or screws over the end grain in
order to hold the panel itself flat while the painter was working on it and before
it could be supported in the frame. Painters of this period who chose to work on
wood often had panels that were thin, less than f inch or 6 mm., and these were
in danger of warping or even of splitting while still in the studio.
Charcoal. Like chalk, this universal drawing material has probably been used
from primitive times. (See figure 7, J.) The kind usually favored is made from
the willow twig, and the description of its manufacture by the painter himself is
adequately given by the early XV century writer, Cennino Cennini (C. XXXIII,
Thompson, p. 19). According to this, a dry willow stick is cut into slips as long
as the palm of the hand and then split or divided like match sticks and these done
up in bundles. The bundles are put Into a baking dish and left in a baker's oyen
overnight. The coals should then be quite black and, if they are too much roasted,
will break easily in the hand. Far Eastern painters are reported to have used
charcoal for preliminary outlines, particularly in ink painting on paper (Bowie,
P- 32)-
Claude Lorraine Glass. For reflecting a landscape in miniature, a black convex
glass was said to have been developed and used by the painter whose name it