ensions, so that the painter could lay them against the fresh stucco
and rub the design through, or pounce it, as we should say, with
charcoal dust, like a stencil. He then coloured it as quickly as he
could. If he made a mistake, or was not pleased with the effect, there
was no remedy except the radical one of breaking off the stucco, laying
it on fresh, and beginning over again. It was clearly impossible to
paint over the same surface again and again as can be done in oil
painting.

No one knows exactly when eggs were first used in fresco painting, nor
does it matter much. Some people used the yolk and the white together,
some only one or the other, but the egg was, and is, always mixed with
water. Some artists now put gum tragacanth into the mixture. It is then
used like water in water-colour work, but is called 'tempera' or
'distemper.' The effect of the egg is to produce an easy flow of the
colour with so little liquid that the paint does not run on the surface,
as it easily does in ordinary water-colours. The effect of the yellow
yolk of the egg upon the tints is insignificant, unless too much be
used. By using egg, one may paint upon ordinary prepared canvas as
easily as with oils, which is impossible with water-colour.

As for the early paintings upon panels of wood, before oils were used,
they were meant to be portable imitations of fresco. The wood was
accordingly prepared by covering it with a thin coating of fine white
cement, or stucco, which was allowed to dry and become perfectly hard,
because it was of course impossible to lay it on fresh every day in
such small quantities. The vehicle used could therefore not be water,
which would have made the colours run. The most common practice of the
Byzantine and Romanesque schools seems to have been to use warm melted
wax in combination with some kind of oil, the mixture being kept ready
at hand over a lighted lamp, or on a pan of burning charcoal. There are
artists in Europe, still, who occasionally use wax in this way, though
generally mixed with alcohol or turpentine, and the result is said to be
very durable. Sir Joshua Reynolds painted many pictures in this way.

With regard to using oils on a dry surface in wall painting, instead of
fresco, Lionardo da Vinci tried it repeatedly with the result that many
of his wall paintings were completely lost within thirty or forty years
after they had been painted. The greatest of those which have survived
at all, the