Historical Painting Techniques, Materials, and Studio Practice

16

products in the dried oil film (19). These short-chain scission products, by

giving the structure a swollen matrix, confer flexibility to the oil film. Earth

pigments are then particularly suitable as grounds on flexible supports. To

speed the drying process of these grounds, artists advocated the use of pre­

polymerized oil (20).

Most of the inorganic components of these colored grounds are hygroscopic

and are not easily wetted by organic media. Free fa tty acids in the oil would

act as surface active agents, and therefore an unpolymerized oil would be

preferable to ensure wetting of the particles and pigment aggregates.

Groen and Burnstock have fo und air pockets with earth pigments bound in

unpolymerized linseed oil (21, 22). This problem can only be aggravated by

the use of an oil with a reduced proportion of free fatty acids (23). The

presence of air pockets makes the ground porous, causing the paint layers

above to "sink in" as the paint medium is drawn down into the absorbent

ground.

Speedy drying achieved by applying the ground as an emulsion, as advocated

in Pierre Lebrun's Treatise, would also result in a porous film because of the

voids formed during evaporation of the aqueous phase (24). The absorbency

of the ground would be particularly problematic with artists such as Guercino

who, in his first phase, painted aUa prima, using the dark ground fo r his

shadows and often applying only one layer of paint. Malvasia, describing

Guercino's technique before the artist left fo r Rome, says that Guercino had

"an extraordinary speed of execution, in one go laying-in (bozzando) and

finishing" (25). In the case of Guercino, the complaints came from his clients

who felt that since they paid Guercino by the figure, they wanted to see the

whole figure, not one in which more than half was drowned in shadow.

Lanfranco and later Giordano were also known fo r their speed of execution.

This speed was castigated by most art theorists, because it was seen as pratica,

simple manual fa cility rather than the fr uit of matured intellectual thought

and skill.

Exposed or thinly covered porous grounds would pose a problem when it

came to varnishing (for the restorer as well as the artist), but grounds suffering

from what the French call lithargeage present a similar problem in appearance.

The coarsely ground lead white would present a less absorbent ground, but

the rough granular surface scatters light, obscuring detail in the worst cases

and flattening the composition. Many seventeenth-century paintings suffer

from this problem (26).

Viewing distance and lighting

It is clear that in a painting such as Guido Reni's Abduction of Helen (Louvre),

which does not depend on the warmth of its shadows fo r the depiction of

depth and its illusion of space but rather on what Leonardo termed aerial

perspective and the diminution of colors, the impact oflithargeage is minimal,

and saturation of the picture surf ace not essential.

This is the case with paintings of what I have termed the "high finish" school;

that is, those by painters who did not paint alIa prima, nor availed themselves

in the Venetian manner of the artifice of large areas of shadow and light, but

rather achieved the illusion of space through "the diminution of the hues, as

much through their quality as through their strength" (27).

The relative importance of saturation in paintings that rely on their dark

ground fo r illusion of space was especially visible in a recent exhibition of

Neapolitan painting in Bordeaux. Two paintings by Caravaggio were hung

next to each other. One was a privately owned Doubting Thomas, with a high

gloss varnish, and the other painting was a Salome with the Head of St. John

the Baptist (National Gallery, London), which had a much more matte ap­

pearance (28).

Historical Painting Tech niques, Materials, and Studio Practice