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Sunday, January 31, 2016

Fwd: Analyzing the King’s Plasters


https://imalqata.wordpress.com/2016/01/30/analyzing-the-kings-plasters/
iMalqata Blog wrote:
Analyzing the King�s Plasters

Alexandra Winkels

This season, I had the pleasure of working with the Joint Expedition to Malqata (JEM) team for twelve days to analyze the site�s archaeological mortars and plasters. As a freelance wall painting conservator and conservation scientist I am performing a research- and PhD project investigating mortars and plasters in Ancient Egyptian wall painting and architecture from the pre-dynastic and pharaonic periods, and into the Greco-Roman period. Malqata, as one of the two preserved ancient Egyptian royal cities, is of course a very interesting place to examine which different mortar and plaster materials have been used for the construction of architecture and the decoration of architectural surfaces.

As the analysis had to be carried out on site, I set up my mobile �field laboratory,� with portable photographic and analytical equipment, in the old mud brick guard house next to the King�s Palace. Though it got a bit crowded at times, I enjoyed sharing the tiny room with hundreds of clay plaster fragments with elaborate bright colored wall painting decoration, uncovered by Peter Lacovara during this season (iMalqata Blog | January 19, 2016).

The little mud brick guard house turned into a temporary little �field lab� and wall painting shelter.

For the comparative analysis of plaster materials from selected archaeological sites in Egypt I am implementing conservation- and natural scientific methods. Besides the analysis of the chemical-mineralogical composition of the original plasters I also investigate and document technological features that reveal the applied plaster and wall painting technology. At Malqata, I collected small mortar and plaster fragments from several areas of the site in 2015 and 2016. These include the King�s Palace, houses of the North Village, and the Amun Temple. Here is a short glimpse of what I found so far.

In the recent analysis, eight major mortar and plaster types, each being processed for individual technological functions, could be differentiated. For example, dark brown clay mortars, with varying contents of plant fibers as organic fillers and reinforcement, were used as basic floor, wall, and ceiling plasters. In some buildings, however, millimeter-thin yellowish- to brownish-white �plaster washes,� containing a high content of calcium carbonate and marl clay, were applied to floors and walls of selected rooms, and onto several throne platforms within the King�s Palace.

Cross section of a yellowish-greyish white mortar with upper thin clay and white wash layer used to set and plaster stones of a bathroom basin (iMalqata Blog | February 16, 2015). Below, the cross section of a dark brown clay plaster fragment with white and Egyptian blue paint layers from a ceiling of the King�s Palace.

The most elaborate treatment was given to apparently more significant throne platforms and sections of floor within the palace. In these places, a fine layer of pure lime plaster covers the visible surfaces of the clay-plastered mud brick superstructure. This plaster type is much more stable than clay plaster as it cannot be dissolved in water.

In terms of wall painting technology, the polychrome wall and ceiling paintings of the King�s Palace were created directly on a smoothed clay plaster surface, without the overall interlaying of fine white wash or paint layer that we see in the painted tombs of the Theban necropolis. Aside from this, traditional construction methods were used in the composition of the paintings on the walls and ceilings of the palace as seen in the photograph below.

Wall painting fragments from the King�s Palace showing lines and drips from a cord string soaked in red color, and traces of red outline drawings that preceded the polychrome paint application.

The color spectrum includes a differentiated use of varying blue and green colors that could be investigated further by visible-induced luminescence (VIL)-imaging (See VERRI, G. (2008): The use and distribution of Egyptian blue: a study by visible-induced luminescence imaging. In: Uprichard, K and Middleton, A, (eds.) The Nebamun wall paintings: conservation, scientific analysis and display at the British Museum. (41 � 50). Archetype: London) Egyptian blue emits a bright luminescence that lies in the infrared range when it is excited by visible fluorescent light. With an infrared-sensitive digital camera, this luminescence can be photographed. A special filter applied in front of the camera lens captures the IR-radiation, but blocks out all visible light. Using this technique, the tiniest traces of Egyptian blue that are not noticeable in visible light can be shown in the digital VIL-image.

In case of the Malqata paintings, the multi spectral imaging method helped to determine that the early synthetic pigment Egyptian blue was used not only in its pure form. Apparently, to achieve brighter bluish green color shades, it was also mixed with Egyptian green and a natural green earth pigment containing glauconite. The latter is a pigment production technique that continued into Roman times.

Wall painting fragment from palace room K1 photographed in visible light and with visible-induced luminescence imaging (levels increased). The outlines of the pure Egyptian blue color application (reduced due to pigment loss) are clearly legible in the VIL image. The bright shining dots in the bluish-green colored paint of the lotus flower show the luminescent pigment grains of Egyptian blue in mixture with Egyptian green.

Detail of a spiral from a ceiling plaster fragment, visible and VIL-image (levels increased); the green colored center of the spiral was painted with a natural green earth pigment containing glauconite. The bright luminescence of pigment grains within the green paint shows the additional intermixture of Egyptian blue.

January 30, 2016