This thesis deals with the treatment and conservation methods of Coptic icons. It consists of the following Studies:
1-Introduction on Coptic Art
Coptic art was introduced in Egypt since the introduction of Christianity in Egypt. It is an art that was influenced by several factors and had it is own features. The artistic features that preceded the Coptic icons are discussed. Also the demolition of Coptic icons, the most famous Coptic artists and the main subjects painted on the icons are dealt with.
2-Different kinds of icons and their preparation
Icons vary in materials and methods of preparation, especially the wooden or linen supports and the various ground layers such as calcium carbonate "Chalk" or calcium sulphate hydrate 'gypsum" or kaolinite or zinc or other painting grounds. Adhesives and binding media were also numerous and differed in their methods of preparation. They were mainly used to bind the previously mentioned fillers. The main adhesives or binding media were animal glue, fish glue, gelatin, rabbit glue, albumin, casein, etc...
Also, the various painting techniques, e.g: Tempra (egg - white, gum Arabic, animal glue), encaustic painting and oil painting were discussed.
3-The different colourants used on icons
The most important colourants that were used for colouring the icons were discussed. Colouring theories and properties of colourants such as refractive index, coverage, particle size, specific gravity and relative density are mentioned. In addition to that, the groups of natural mineral colours and organic dyes are dealt with, e.g.:
**White colourants: gypsum, zinc, titanium.
**Red colourants: red ochre, kermes
**Yellow colourants: yellow ochre, osfor
**Blue colourants: Egyptian blue, indigo. and other colourants such as: violet; brown and black.
4-Deterioration Factors of Icons:
The physical deterioration factors that affect the wooden support, the gesso layer and the colour layer are the change of relative humidity in the environment around the icon. The different layers contract and expand according to the changes. As a result the icon may deteriorate.
In addition to that an increase on relative humidity encourages biological attack. Heat, which is another physical factor causes embrittlement and weakening of the wooden support, the gesso layer and the binding media (animal glue), as a result the surface of the icon and the wooden support deteriorate.
Light, another physical factor, causes fading or weakening of colourants. The chemical deterioration factors, which decay the support layers for the colourants, are sulphur oxide, ozone, nitrogen oxides, gases, etc.....
Insects and fungi are the major biological deterioration factors, that attack icons under certain conditions.
Last, but not least, man-made deterioration factors are a major problem. They could be due to destruction on purpose, touching the icon as a blessing or incorrect restoration within the Egyptian church.
5-Investigation and Analysis of an Icon.
The importance of using modern scientific methods, for investigating and analyzing the ground layer or colour layer, is considered.
I.R., U.V. and X.ray radiography are sources used to reveal the condensed layers which are not evident to the naked eye, cracks or previous restoration.
I.R. and U.V. spectroscopy are used to identify the binding media in the ground layer or colour layer.
Scanning electron microscopy is used to study the deterioration forms of all the layers of an icon.
6- Methods of Treatment and Conservation of Icons.
There are various methods and materials that can be used for cleaning wax, soot or fly secretions from an icon's surface. Also, old and new varnish layers may be cleaned or removed when blooming occurs. In cases where cracks, pitting or separation of the icons layers are evident treatments may be applied. In some cases, where the wooden support is badly deteriorated, the linen support with all the drawings may be removed. After that the wood may be completely treated and consolidated.
Another point of treating Coptic icons is the retouching or repainting of colours and the use of new varnishes after cleaning an icon, in order to retain its ol glamour.
The last step of treating an icon in a museum or church is to exhibit it under suitable conditions.
The various methods for preparing an icon according to the old techniques were applied by the researcher. These new icons were artificially aged and treated. Therefore, it was possible to choose the most suitable treatment for ancient icons, before application.
Several painting grounds were prepared, according to different references. These grounds were then coloured by using organic or mineral colours. They were all placed in a drying oven at high temperature and high humidity, as a means of artificial ageing.