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Subject: Weeping oil paint

Weeping oil paint

From: Andrea di Bagno <adibagno>
Date: Wednesday, November 21, 2007
Jenny Schulz <jennyal [at] gmx__li> writes

>Contemporary paintings in danger. I am working on a painting by Otto
>Piene from 1993 where white oil paint became liquid within a few
>months and has created sticky drips up to 20cm long. ...

We have in our lab at this moment a painting by John Alexander
painted in 1983 where some, not all, of the black paint is
deliquescing. This phenomenon is occurring in a greater extent in the
larger impasto and just beginning in some of the smaller ones. The
phenomenon seems to start in the center where the paint is thickest.
It is not occurring at all in some of the thinner areas.

It would be wonderful to understand why this is happening. Better
yet would be to figure out if there is anything that can be done to
avoid this from happening.

The only analysis was performed so far is FT/IR. The only
conclusions that were made were that the paint media is likely to be
a mixture of pure oils with alkyds or alkyds with amounts of added
alcohol. The only significant spectral differences between the
deliquescing and stable blacks occur in C=O and C-O bonding regions.
The stable blacks may contain a higher amount of alkyd based upon
the correlation of the main C=O peak with alkyd standards.

There are two main possibilities: first that the dripping blacks are
converting slowly to the dripping blacks via chemical rearrangement
(hydrolysis?) the second that the artist used different proportions
of paint to create his blacks one of which is inherently flawed and
prone to degradation (by hydrolysis?).

Clearly we need to research this further. I am looking into
analysing our samples by GC/MS but we do not have the capabilities
at the moment. Any information would be greatly appreciated.

Andrea Guidi di Bagno
Chief Paintings Conservator
Museum of Fine Arts, Houston

                  Conservation DistList Instance 21:33
                Distributed: Wednesday, December 5, 2007
                       Message Id: cdl-21-33-005
Received on Wednesday, 21 November, 2007

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