Page 246

246                            PAINTING            IN  FRESCO.
is the last or finishing coat of plaster, and requires to be very thinly
and evenly laid upon others
of substantial mortar, which should be previously applied and finished in
the usual manner of a
carefully-prepared wall.
     66. The durability of fresco-paintings is so dependent upon the preparation
of the wall, that
the utmost care in this particular is necessary.  The quality of the lime,
sand, and all the materials
employed, should be unquestionable; and none but the most skilful and reliable
workmen should
be trusted in the work.  The final coat of plaster should be laid under the
artist's eye, if not by
his own hand.
     The progress of a work in fresco being thus by portions, each of which
n~ust be completed at
once, renders it necessary that a cartoon or drawing of the whole should
be previously prepared,
as well as that the arrangement of color and general effect should be decided
beforehand.         These
cartoons require to be made on strong paper.      Over the last rough plastering
a general indication
of. the whole subject should be traced.  This may be done in various ways.
The most common
method, in small works, is, to prick the outlines through with a needle to
a separate sheet of paper.
and, by means of a small bag of thin muslin with powdered charcoal, to pounce
the outline through
to the wall; or to trace it thereon with a blunt point or style, which is
the most common prac-
tice.   This serves as a guide to the final coat of plastering, which is
to receive the painting,
so that the artist can proportion eac[i day~s work with cxactness, and receive
assistance in his
operations.
     The final coat of plastering laid over just sufficient space for a day~s
work, a more elaborate
tracing is made thereon, and the artist proceeds, with all possible celerity,
with his work, in which
a greater difficulty occurs with regard to the appearance of the colors in
a Wet state than in tem~
pera; for allowance has not only to be made for the variation between a pigment,
or tint, in a moist
or dry state, but for the peculiar action thereon, both by the lime and absorption
of the wall. Fresco-
tints may be fully developed on an old or dried wall in a few days, while
on one recently plastered
as many weeks may elapse before they assume their permanent appearance.
     67. The colors are ground in water and kept ready for use in pots. 
No size is necessary,
except perhaps a very little for such pigments as ultramarine, charcoal black,
etc., and even then
with very questionable propriety; the adhesive property of lime combined
with water being the
only reliable medium for coloi' in fresco, and its durability dependent upon
its perfect incorporation
with the plaster.
     Not only the original pigment9, but also as many tints and combinations
as may be required,