308 PAINTING MATERIALS

linseed, which has been dried over the fire and ground to a powder, is heated with
water, wrapped in linen, and put into such a press as was used for extracting the
oil of olives, of walnuts, or of the poppy.

Proportional Divider (see Compass, Divider, and figure 9, r).

Punch or Stamp. During the centuries when painters were occupied with
making altarpieces that had backgrounds of gold leaf, there was a varying but
general use of small instruments for stamping figures in the haloes and other details
that were described in the gold. Few references to the nature of these instruments
occur in contemporary literature, Thompson (The Practice of Tempera Painting,
p. 69) suggests that a variety of punches could be made with brass rods as the
shafts, the ornaments to be filed or incised at one end.

Quill, the tube or barrel of a feather; this has had much use in painters' tools
(see Brush, Pen, and figures i and 19).

FIGURE 20. The ruling pen: (a) as seen from the side, showing the general shape of the
blades; (jK) a compass with a ruling pen, showing the slot between the two blades of the
latter.
Rack. Small strips of ivory or wood, cut with short, semi-circular grooves in
the upper edge, have been used as a place to lay brushes during painting, par-
ticularly of water color and miniatures. The purpose is to hold the fine tip of the
brush away from the work-table and to keep it from rolling. These no longer ap-
pear in catalogues but were frequent in the middle of the XIX century and prob-
ably had been used for an indefinite time before then.
Reducing Glass, a double concave lens which diminishes the appearance of
size in objects viewed through it; often used by painters as an artificial means of
getting a distant point of observation of their work.
Rest Stick (see Mahlstick).
Ruling Pen. Developed evidently during modern times as an instrument of
precise draughting, this differs from the typical pen made from reed, quill, or
steeL Instead of being a section of tubular shape, tapered to a point or nib, it has
two parallel sides and the drawing edge is between the ends of these (figure 20).
The width of the line described is regulated by their distance apart, and this is
adjusted by a small set screw. A variety of sizes is manufactured. Most ruling
pens are straight, but a curved pen for particular purposes is available, and ruling
pen attachments for compasses are now the usual means of drawing circles with
ink.