Colnaghi Foundation Journal 03 - Page 175



172
Scientific intervention in two major Murillo canvases
Scientific intervention in two major Murillo canvases
The areas containing figures worst affected coincided with
the losses in preparation and the paint layer, mentioned
above in the radiographic study.
The treatment of the stretcher involved cleaning the
wood surface, preventive measures against insects,
and strengthening and repairing the wood. The
considerable accumulation of surface deposits on both
sides of the work was eliminated through controlled
suction. The losses of shape in the support were treated
with the canvas in a horizontal position, protecting the
area to be treated and alternating weight, damp, and
controlled heat.
The Miracle of the Loaves and Fishes was in a delicate state,
with the ground, priming, and paint layers in danger of
becoming detached. Certain areas were therefore fixed
before removing varnishes and earlier re-touchings,
and a second fixing applied across the whole work after
cleaning. In Moses and the Water from the Rock of Horeb
fixing was done after the paint layer was cleaned.
Using the solubility test and micro sampling in strategic,
barely visible, areas, the most suitable solvent was
selected for cleaning the paint layer, removing varnishes
and earlier re-touchings, whilst avoiding alterations and
reactions with the original (fig. 17).
Fig. 17 / Witnesses of cleaning
Fig. 18 / Coating phase.
The layer of varnish in both pictures was three times
thicker than normally found in other canvases, being 80
um thick in some places. This indicated the re-touchings
of previous interventions in the induced ultraviolet
light fluorescence study (figs. 15 & 16). The varnish,
though, appeared as an opaline, greenish veil applied
unevenly, forming a screen obscuring the colours of
previous periods. It was therefore necessary to resort to
radiography to determine the exact size of the losses.
In the vertical side edges of both pictures, a chromatic
reintegration with even tones and vertical lines coincided
with the stuccoed area of previous interventions, whose
width in some places could be as much as 9 um.
Removal of the thick layer of varnish and overpainting
revealed areas of wear in the paint layer previously
hidden. Of particular importance were the chromatic
variations typical of pigment alteration, as in cobalt
blue or smalt, which had lost their original colour and
turned into a brownish-grey layer giving a very different
appearance to a large part of the cloudscape. The loose
and quick brushstrokes in this area, where the marks of
the brush are quite broad, also became apparent.
After the first application of varnish to the surface,
the losses were filled, with a greater number in the
Moses and the Water from the Rock of Horeb (fig. 18). The
new in-fillings were attached firstly with a water-based
technique and then with pigments mixed with varnish,
aiming at a harmonious and balanced formal reading
and aesthetic perception of the painting. Finally, a
protective layer of pulverized varnish was applied.
173

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