October 1999
Painting Techniques and Materials
The
murals were painted directly on the gray plaster exterior walls (Portland
Cement). The wall surfaces were prepared with a glue sizing and white lead
oil-priming layer prior to execution of the mural. The artwork was smoothly
painted with an oil-like medium paint with no impasto except for the somewhat
gritty texture of the wall surface beneath. Burnt sienna colored under drawings of the bold design forms are visible
in areas where the upper layers of paint have weathered and flaked away. To
develop the design, one to three coats of oil paint were employed. Upon completion, a natural resin varnish was then applied to the surface.
Condition:
The
somewhat impermeable, embrittled white lead ground layer exerts tension on the
inherently weaker hygroscopic glue size layer. This has contributed to the weakened bond between the paint and ground
layers from the wall leading to eventual paint loss. From the cross section
analysis, it appears that some restorations were made to the murals prior to the
first overpaint application. This
finding substantiates early reports of attempts to consolidate insecurities in
the mural soon after it was completed. The
painting was subsequently overpainted entirely with an oil paint which is
extremely cross-linked and difficult to remove. A synthetic resin type of
coating was applied selectively to this first coating. One to three coats of latex overpaint was subsequently applied.
Evidence of a clear synthetic resin coating was found to be applied
between the multiple overpaint layers. Wolbers concludes that the tension
exerted by the multiple layers of overpaint is resulting in shearing of the
overpaint from the mural’s surface. (Click here for
Wolbur's report)
The
majority of the surface of the murals lie under one to four layers of overpaint.
Many areas are characterized by active cleavage, flaking paint, paint loss (both
inter-layer and from the wall substrate), shearing overpaint and fading of
exposed original paint.
While
fading from prolonged exposure to intense sunlight and damaging ultra-violet
light and heat is present, it is impossible to determine to what extent the
artwork has been altered. Where original paint has been exposed, fading is
evident and appears extreme. Where
the original paint has been protected by overpaint, the colors are much more
vibrant.
Not
only has light caused damage, but also the exposure to harsh climatic conditions
has taken its toll. On the murals with the most direct and prolonged exposure to
sunlight, the layers of overpaint and the original paint layers have been
unevenly and sporadically weathered away.
Condensation
on the surface of the murals is another factor leading to deterioration. The Star report of 1996, noted “significant condensation on the mural
surfaces on foggy, humid days”, both summer and winter”(4). This condition,
on the unprotected damaged surfaces has undoubtedly resulted in active response
by the Portland Cement, leading to delamination.
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The
examination involved a direct inspection of the entire surface of all of the
murals to ascertain the security of the paint films and their condition.