114
On cloth and sindone it is more necessary that this colour should be layd
on twice, wile tempered with size, bif
ore it is put on Jor the last coat
tempered with white oj egg. And this is because sindone and cloth, owing
to their porosity, are too absorbent, flowing, flexible, and unstable, and
theri
f
ore soak up the colour, so that there does not remain a good and firm
substance oj colour upon the cloth or sindone, unless, as usi
f
ul experience
tells us, it is laid on several times.After the first layer was applied, the surf ace of the canvas was burnished to
receive the second layer and finally a last layer and gilding (21):Let those things dry which you have drawn and painted, and when they
are dry burnish them, that is, polish or smooth them gently with a tooth
oj a horse or a boar, or with a polished hard stone fitted Jor this purpose,
in order that all the roughness may be softened down, ... and again paint
over and draw upon those same places, with this colour, as bi
f
ore, and
af terwards let it dry, and then polish and burnish it as bif
ore. Af terwards
go over and repaint those places which you did bifore, with the same
mordant or colour, but let this third and last coat oj colour be tempered
with white oj egg ....Sometimes painters tried to prepare the medium in such a way that it retained
a workable consistency without being heated. This is why some recipes, in
cluding the fo llowing two recipes, survive fo r keeping glue fluid during prep
aration without heating it: "If you have the time, allow the mordant to get
stale, fo r several days or weeks, fo r it will be better putrid than fresh" and "if
you want to keep it liquid, put in more plain water, and let it stand; and after
a few days it will stay liquid without heating. It may smell bad, but it will be
very good" (22, 23).Others describe adding more water and vinegar with honey to the dissolved
glue (24). The next day the vinegar is poured off, and clear water is added
and heated. When it cools, the glue is stored and eventually becomes liquid.
The small amount of vinegar soaked up by the glue also seems to help pre
serve it. The De Arte Illuminandi says, "And know that it is a very good plan
to soften parchment or stag's horn glue with the best vinegar; and when it
is softened, and the vinegar poured off, add plain water and melt it, and
proceed as has been said" (25). Pigments were mixed with this medium in
much the same way as with egg tempera, presumably by first grinding them
in water and then adding the medium.Painted on fine linen, the Adoration measures 54.6 em X 69.2 em. Judging
by the age and type of strainer, it is reasonable to presume that the painting
was removed from its original support, which could have been a panel or
another strainer as described in the Alcherius manuscript. This would pre
sumably have been carried out in the early nineteenth century fo r the pur
pose of mending two horizontal tears. Presumably to repair this damage, a
lining canvas was applied to the back with an animal glue or starch paste. In
what is preserved of the original canvas, no tack holes or pronounced stretch
marks (called "scalloping") are visible. This might indicate that the canvas was
glued to its support, either a panel or a strainer (26). Two paintings by Man
tegna with their original supports still exist. One is the Ecce Homo at the
Musee Jacquemart Andre in Paris, which is glued to a panel, and the other
is the Presentation at the Staatliche Museen in Berlin, which has its original
strainer (Fig. 3) (27). A slightly raised edge on the top might indicate that
the Adoration had an engaged frame, such as the Berlin Presentation, which
has a series of splinters adjacent to the painted frame with the color con
tinuing up along these splinters. An example of an engaged frame survives
(Metropolitan Museum of Art, Lehman Collection) that has a remnant of the
original canvas by an unknown artist sandwiched between the strainer and
the frame (28).Historical Painting Techniques, Materials, and Studio Practice