Of Painting in Tempera,[198] or with egg, on Panel or Canvas, and how it
is employed on the wall which is dry.
§ 82. _Painting in Tempera._
Before the time of Cimabue and from that time onwards, works done by the
Greeks in tempera on panel and occasionally on the wall have always been
seen. And these old masters when they laid the gesso ground on their
panels, fearing lest they should open at the joints, were accustomed to
cover them all over with linen cloth attached with glue of parchment
shreds, and then above that they put on the gesso to make their working
ground.[199] They then mixed the colours they were going to use with the
yolk of an egg or tempera,[200] of the following kind. They whisked up
an egg and shredded into it a tender branch of a fig tree, in order that
the milk of this with the egg should make the tempera of the colours,
which after being mixed with this medium were ready for use. They chose
for these panels mineral colours of which some are made by the chemists
and some found in the mines. And for this kind of work all pigments are
good, except the white used for work on walls made with lime, for that
is too strong. In this manner their works and their pictures are
executed, and this they call colouring in tempera. But the blues are
mixed with parchment size, because the yellow of the egg would turn them
green whereas size does not affect them, nor does gum. The same method
is followed on panels whether with or without a gesso ground; and thus
on walls when they are dry the artist gives one or two coats of hot
size, and afterwards with colours mixed with that size he carries out
the whole work. The process of mixing colours with size is easy if what
has been related of tempera be observed. Nor will the colours suffer for
this since there are yet seen things in tempera by our old masters which
have been preserved in great beauty and freshness for hundreds of
years.[201] And certainly one still sees things of Giotto’s, some even
on panel, that have already lasted two hundred years and are preserved
in very good condition. Working in oil has come later, and this has made
many put aside the method of tempera: in so much that to-day we see that
the oil medium has been, and still is, continually used for panel
pictures and other works of importance.