الفهرس 
Solubility parameter of HildebrandOnly 14 pages are availabe for public view
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Abstract
Cleaning of oil paintings is a delicate conservation procedure through
which the conservators aim to enhance the readability and appearance of
paintings to their original states. For this purpose, cleaning procedures as
the removal of discolored varnish layers and any extraneous material
deposited on the painted surface over time may be required. Organic
solvents are widely used for conducting this procedure. An important
start to estimate the impact of oil painting cleaning is to well understand
the solubility changes of oil painting materials with aging. However, the
natural chemical alternations of oil painting materials are already
complex, the possible additional alternations could be induced by solvent
exposure. In this context, systematic studies were carried out to evaluate
the tangible and intangible solvent effects on oil paint formulations.
Besides, the controversial concerns of the conventional organic solvents
used for oil painting cleaning, their potential hazard emissions have a
potential risk not only to the healthiness of conservators but also to the
indoor environment contamination. Recently, green materials have been
supported in conservation practices aiming to have a low impact on the
conservators' health and environment. This is available today in some
methodologies in cleaning practices as gels, aqueous cleaning systems,
and bio-cleaning which mainly aim to avoid and minimize the use of
toxic solvents. Bio-based green solvents are benign alternatives to
conventional petroleum solvents that fulfill the twelve principles of green
chemistry. In this context, bio-based green solvents' effectiveness will
need to be investigated in the field of oil painting cleaning.
This thesis is divided into three chapters. Chapter I includes the
technical conception of oil painting cleaning with a description of the
cleaning methods that must be chosen according to the physical and
chemical nature of the unwanted deteriorated materials. It also involves
the principles of solvent selection for cleaning with clarification of
solubilization theories and solubility parameter systems and the required
physical properties of solvents that could affect the cleaning procedure.
The changes in solubility of oil paints, natural varnishes, and synthetic
polymers are also mentioned in this chapter. The potential risks induced
by solvent-based cleaning from tangible and intangible effects on the oil
medium besides their toxic effects on the operators' health and the
ambient environment are also discussed. Description of the bio-based
green solvents, sources, and their properties are also interpreted in this
chapter.
Chapter II includes the condition assessment and technical analysis of
Mohamed Ali Pasha portrait which was dedicated to the National Military
Museum at Saladin Citadel in Cairo. Multispectral imaging, cross-
sections, stereomicroscope, scanning electron microscope coupled with
dispersive energy of X-ray spectrometer, Attenuated Total Reflection-
Fourier transformed infrared spectroscopy, Gas chromatography-Mass
spectroscopy, and X-ray diffraction were employed for technical analysis
and assessment of Mohamed Ali painting conservation state. The
technical analysis includes the stratigraphic structure of the original
painting and the previous additions of conservation interventions. The
ground layer is mainly composed of high proportions of barite, calcium
carbonate, and low proportions of zinc oxide and basic lead carbonate.
The binding medium was confirmed to be linseed oil. Carbon black, burnt
sienna, green earth, yellow ochre, ultramarine, and a mixture of red lead
and hematite were detected in the painted layer of the painting. Dammar
varnish was also identified as a final varnish. The painting was previously
conserved more than once; the different varieties of verse patches applied
to the original canvas confirmed the multiplicity of conservation
interventions. This chapter also includes the experimental study through
which two groups of mockups with the same stratigraphy of Mohamed
Ali painting and thermally aged. The two groups mainly aimed to study
how the different types of oil paint contents either having a catalytic
effect on the drying process or not could affect their sensitivity toward the
solvent during the cleaning of painting. Five bio-based green solvents
were studied with one more inappropriate non-polar solvent. The
experimental study included the investigations of the laboratory-prepared
samples by the means of atomic force microscopy (AFM), and scanning
electron microscopy (SEM). The soluble organic components of the oil
binder that may be extracted from the paint films will be characterized by
gas chromatography-mass spectrometry (GC/MS). Attenuated Total
Reflection Fourier transform infrared spectroscopy (ATR- FTIR) was
employed to evaluate the efficacy of the cleaning procedure and to study
the possibility of carboxylate fatty acids migration within the paint layer.
The likelihood of the bio-solvents retention was identified with
thermogravimetric analysis (TGA), and the possible total color difference
of the painted layer surface was measured by a colorimeter. from the
experimental study, dimethyl carbonate proved its efficacy for cleaning
because it did not show high swelling by comparing with the other bio-
solvents used in the experimental study along with no showing changes in
palmitic and stearic acids proportions by comparing with the proportions
of the varnished references. In addition to that, it has low retentive time
inside the painted layer.
Chapter III includes the scientific conservation procedures that were
taken to Mohamed Ali's portrait. The painting was cleaned with dimethyl
carbonate which confirmed its effectiveness in cleaning the experimental
mockups. The practical study did not stop at the cleaning of the painting.
The removal of the back patches from the previous conservation
interventions, lining, stretcher cleaning and coating, frame conservation,
ground layer filling, retouching, frame conservation, and final
varnishing was carried out to retrieve the historic and aesthetic values of
the painting.