Laser cleaning of Ancient Egyptian Wall Paintings in the Tomb of Neferhotep TT49

Here at the Reading section of digitalEPIGRAPHY, we like to broaden our scope from time to time and draw your attention to interesting new projects that utilize the latest technologies in the service of preserving and understanding Egyptian art (Scanning Seti, Wadi el-Hudi expedition, Color the Temple etc.). This time, we’d like to showcase a project that used laser technology to remove dirt and soot from the fragile wall paintings of an ancient Egyptian tomb – a technology that may become a tremendous aid in the future of epigraphy. The project involved three German conservators, Susanne Brinkmann, Birte Graue and Christina Verbeek.  

The Tomb of Neferhotep (TT49) is located in the necropolis on the west bank of Luxor. Since its rediscovery in the 19^thcentury, the tomb has seen extensive damage due mainly to human habitation and pollution. Large areas of the wall decoration are covered with thick layers of soot and dirt, rendering most of them unreadable. As part of recent conservation efforts, an international team of scientists has been testing various cleaning methods, including laser cleaning, for the tomb’s challenging surfaces.

fig. 7.15 Detail of the wall painting before and after laser cleaning.

Project description

The Tomb of Neferhotep (TT49) was built in the reign of Pharaoh Ay, around 1320 BC. When the tomb was rediscovered in the beginning of the 19^th century, the wall paintings were still in relatively good condition. However, the tomb was subsequently used for housing and keeping cattle. Also, an annex room inside the tomb was used for burning mummies. For these reasons, thick layers of soot are covering much of the wall paintings and decorative surfaces, especially the ceilings and upper parts of the walls in the pillar hall. Since 1999 an international team of Egyptologists, archaeologists and conservators from Argentina, Brazil, Italy and Germany has been working on the study and conservation of the tomb.

As part of the conservation work non-destructive cleaning methods were developed for the very fragile wall paintings and colored stone surfaces. Besides mechanical and chemical methods, laser cleaning was also tested. 

Laser cleaning is a non-contact media-free method that enables conservators to successfully remove firmly attached dirt and soot particles from fragile surfaces, such as wall paintings, in a non-intrusive way. In the Tomb of Neferhotep, the conservation team used the portable light weight backpack laser from cleanLASER systems.

“For conservation work in the tomb in Egypt a mobile device is required. Besides a flashlight pumped Nd:YAG-laser with Q-switch, a battery powered backpack fiber laser was tested. The application of a small size, light weight fiber laser is a new approach… The implementation of laser cleaning with a fiber laser in combination with mechanical and chemical cleaning methods brought previously unreadable depictions of ancient Egyptian Art in Thebes to light.”

Conservation program

The first step of the conservation project was the extensive survey and comprehensive documentation of the tomb. The latter included the digital photographing of the entire tomb, which was done to obtain the photographical basis for the mapping. “The digital mapping with MetigoMAP (Focus GmbH Leipzig, Germany) includes the technological characteristics, current condition and damages as well as ongoing treatments.”

In order to develop a cleaning method for the fragile soot-blackened surfaces of the tomb, first, “the composition of historic materials and overlying soiling is analyzed to find out about their chemical and physical properties as well as their alteration and sensitivity.”

“Due to the very complex impairments, different methods like mechanical and chemical cleaning were tested. In specific areas of the paintings, chemical and mechanical cleaning proved to be successful. But in the very sensitive areas of fragile paint layers of high water or solvent sensitivity, like the white backgrounds, the traditional cleaning methods were not suitable. With regard to the problem of cleaning the soot-darkened white backgrounds, the laser cleaning was considered because it could optimize the cleaning results with a selective ablation process, thus avoiding side effects while preserving the historical layers behind the black soot crusts.”

Pre-testing the laser cleaning systems

A pre-testing was carried out first in the laboratories of the Fraunhofer Institute and of cleanLASER on samples of “soiled limestone, a fragment of plaster with paint layer, colored clay shards and a soot covered sample plate with a reconstruction of an ancient Egyptian painting.”

For these tests the light weight backpack cleanLaser system CL 20 fiber laser was used besides a flashlight pumped Nd:YAG-laser with Q—Switch, which is commonly used in conservation. This battery powered fiber laser weighs only 12 kg, making it easy to transport and handle. “The user operates the scanning end effector of the laser by moving a hand piece with integrated scanner parallel to the object surface. The operating parameters can be regulated on this end effector. The combination of these parameters offers the possibility for an easy and precise regulation of laser intensity.” This very progressive action of the laser allows for softly thinning the soot layers pulse by pulse.

Following the testing of the samples, “the sample areas are examined with a microscope looking for alterations (color, material loss, surface alteration such as melting etc.). The testing is firstly to detect if in general a selective reduction of the soot crust without damage to the supporting surface (plaster, limestone, paint layer) is possible and secondly to define parameters.”

The laboratory pre-testing promised very good cleaning results, therefore the conservator team commenced testing in the tomb itself.  

“The first cleaning tests in the tomb were carried out on undecorated soot covered areas to find suitable parameters for the reduction of the dirt layers. The laser treatments on different surfaces were carried out on defined sample fields which were examined with a microscope before and after treatment.”

After analyzing the results, further laser cleaning possibilities were approved on polychrome surfaces as well.

Results of laser cleaning in TT49

“A reduction of the soot layers on undecorated as well as on decorated stone surfaces and wall paintings in the tomb of Neferhotep is possible with the backpack solid state laser system. The cleaning results are highly consistent and efficient. 

On stone surfaces a combination of chemical and laser cleaning brings about the best results. Because of the porous structure of the stone oily and fatty components of the soot have penetrated into the surface thus it is not possible to remove extremely thick soot crusts with no residues.

Good results were evident on the white background paint layers where a self-regulating work process and the selective ablation of the soot layer was conducted without interfering with the underground. The laser treatment does not cause any harm to the fragile paint layers, just a thin yellow – transparent patina remains on the surface.

The cleaning tests in polychrome areas show that the treatment needs a differentiated approach to specific situations.  The nondestructive soot reduction of red, yellow and green was possible after determining suitable laser parameter. The Egyptian blue and green pigments can be treated without color alteration.”

In conclusion, “it was possible to reduce the soot and dirt crusts on broad areas of the Old Egyptian wall paintings in the tomb-chapel of Neferhotep by the help of portable backpack fiber laser equipped with rechargeable batteries. In order to soot reduction on different surfaces of stone, plaster and wall painting a combination of mechanical, chemical and laser cleaning showed the best results.”

Visual examples

fig. 7.16 Portrait of Neferhotep before, during and after treatment with chemical, mechanical and laser cleaning methods.

fig. 7.1 Since 2004, after intensive testing, the soot covered paintings have been cleaned by a solid state laser.

fig. 7.11 Removing thick soot layers from the paintings. A rapid pulsed laser beam scans across the treated surface.

What we like

• The role of technological innovations in the service of recording, documenting, preserving and restoring cultural heritage has increased drastically in recent years. Digital tools such as photogrammetry, 3D modelling, drawing boards, etc. are already utilized by many areas of modern archaeology. Similarly, laser cleaning could play a central role in the future conservation of ancient Egyptian wall paintings which are in such fragile condition that other cleaning methods are out of the question. 

Additional reading

This Reading entry was based on the following articles:

“Laser Cleaning of Ancient Egyptian Wall Paintings in the Tomb of Neferhotep TT49” by Susanne Brinkmann & Christina Verbeek (CTT - Conservation of Theban Temples an Tombs
Symposium proceedings February 2016, Luxor), which you can read here.

“PROCON TT 49: Laser cleaning of ancient Egyptian wall paintings and painted stone surfaces” by B. Graue, S. Brinkmann & C. Verbeek (Lasers in the Conservation of Artworks VIII – Radvan et al. (eds), 2011), accessible from here.

Of cleanLASER and its laser technology you can read further on the company’s website.

Précis and commentary by Júlia Schmied