Further moisture treatment from the back was necessary, but a
slower, more even drying process was desired. Therefore, moisture was
sprayed onto the back with a pressurized fine-spray humidifier, and the
panel was placed facedown on a Melinex interleaf. Fine linen canvas
and then hessian (burlap) webbing were placed over the back to form a
moisture-retention layer as well as an evacuation layer, which allowed
a slower drying under a slight vacuum. The procedure, which was con-
tinued for a day with the dehumidifier, brought the room RH back to
55% at 21 °C. Afterward the panel showed a flatter plane.
Under raking light the uneven thinning of the original panel
showed ripples and distortions. Two suitable interleaf materials were
required. After the application of the first interleaf, the undulations in the
panel were evened out with a filler and then isolated with a second inter-
leaf before attachment to the balsa-wood buildup. A combination of
muslin and then Stabiltex (a very finely woven polyester) was used. Fine
muslin was prestretched on a strainer and coated on both sides with three
coats of Beva 371. The panel was put facedown on Melinex over thick blot-
ting paper on a board on the low-pressure table, and the strainer with the
impregnated muslin was placed over the back. A sheet of silicone Melinex
was placed over the Beva-coated area of the panel, the whole was covered
in Melinex, and a vacuum was applied.
With a heated spatula, the muslin was then bonded to the back
ofthe panel through the silicone. When it had cooled, the vacuum was
released. Now the panel was attached and could be easily handled on
the strainer.
During these treatments, the table was usually at about 30 °C; the
table’s built-in dehumidifier helped maintain the temperature by control-
ling the RH level. An overall infill of Fine Surface Polyfilla was applied on
the back ofthe hessian webbing and sanded flat when dry.
Acoat of Beva 371 was applied over the leveled layer of Polyfilla;
a second interleafwas prepared by prestretching Stabiltex on a strainer
and applying three coats of Beva 371 on both sides.
The first strainer on which the muslin and panel had been
attached was detached. To make sure the painting had adopted a satisfac-
tory surface, it was placed faceup on the board, with webbing under the
muslin up to the edges of the panel, and covered with Melinex. A vacuum
was then applied and the surface observed: the improvement was marked.
For the application of the Stabiltex layer, the painting was laid
facedown on Melinex, and blotting paper and webbing were laid up to the
edges of the panel over the visible edges of the muslin. The new strainer
with the Stabiltex was laid over the painting; silicone was laid over the
panel; and then the whole was covered in Melinex and a vacuum applied.
The Stabiltex layer was then attached with a heated spatula.
The picture was then taken offthe table and kept on the strainer in
preparation for the next step, a balsa-wood buildup. Planks of balsa measur-
ing 12.7 3 63 cm were prepared on the table. In this instance, it was decided
to put two layers of balsa running with the grain of the original—as
opposed to the normal practice of putting the first with the grain and the
second against the grain. This variation was chosen because it was thought
to reduce slightly the strength of juxtapositioning, as well as to reduce the
chance ofany restriction if the panel should move. The balsa wood in this
instance was cut across the grain at 2.5 cm intervals to half of its depth, so414 Reeve