Collaboration between community, religious heads, management, historians and conservation scientists is a remarkable involvement for the sacred cause of Conservation and Preservation of wall paintings of Sri Harmandir Sahib Ji. The conservation approach has to deal with multiple interwoven issues. Some points to consider were:
- Whether we need to explore the under-drawings, belonging to various eras, at this stage
- How to make conservation work possible with the huge number of pilgrims visiting the site at all times
- How much intervention is required, since we are dealing with paintings with many levels of retouching and a mixed media. The paintings have water based, oil based and acrylic paints used simultaneously.
- Creating awareness regarding importance of Preventive Conservation Measures that need to be followed regularly. The aim of preventive conservation is to create favourable conditions minimising decay, and to avoid unnecessary remedial treatments, thus prolonging the life span of wall paintings. Appropriate monitoring and the control of the environment are both essential components of preventive conservation. Inappropriate climatic conditions and moisture problems can cause deterioration and biological attacks. Monitoring can detect initial processes of decay of the painting or the supporting structure, thus preventing further damage. Deformation and structural failure leading even to possible collapse of the supporting structure, can be recognised at an early stage. Regular maintenance of the building or the structure is the best guarantee for the safeguard of the wall paintings.
- Inappropriate or uncontrolled public access can lead to their damage. This may necessitate the limitation of visitors and, in certain cases, involve temporary closure to public access. However, it is preferable that the public should have the opportunity to experience and appreciate wall paintings as being part of the common cultural heritage. It is, therefore, important to incorporate into the site management careful planning of access and use, preserving, as far as possible, the authentic tangible and intangible values of the monuments and sites.
- Conservation treatment can be performed only after gathering all necessary pertinent information as well as investigating and assessing the causes of actual or potential deterioration. Examination and treatment include the recording and documentation of the methods and materials used by the artist and by the conservator.
- Conservation and restoration treatment are undertaken in order to stabilize, consolidate, clean, repair, remove non-original additions, strengthen or reassemble an object, or return it to the appearance of a known previous state by means of physical or chemical intervention.
- Preservation of the physical, historical and aesthetic integrity of the paintings should take precedence over all other considerations.
- Conservation treatments should employ techniques and materials which, to the best of current knowledge, will neither endanger the true nature of the object nor impede future treatment or the retrieval of information through scientific examination.
- All conservation examination and treatment must be conducted in an ethical manner and with full respect for the object, within the highest possible standards of practice.
- Assessment of the Physical Condition of the wall paintings: A prerequisite to any conservation treatment program is the assessment of the physical condition of the objects. Initial thorough assessments in the form of surveys should be updated and augmented periodically in order to ensure the preservation of the paintings.
Assessment of Damage
There are three broad categories of damage:
- Paintings that are hidden under stubborn layers of dark grime
- Paintings that are varnished. (varnish is aged and hence yellowed)
- Paintings that are covered by glass
These three categories are not uniform as far as damage is concerned. Each category can be further divided into sub-categories based on extent and type of damage.
Category-1 Paintings hidden under layers of dark grime can be sub-divided into three sub- categories:-
- Thinner Grime covering delicate remains of original paintings
- Stubborn Grime covering the repaired painted/gilded structural elements
- Thick grime layers along with paint/gilded layers cracked and flaked
Category-2 Varnished areas can further have:-
- Paintings having flaking and loss.
- Paintings retouched by unsuitable paint media, thus forming films, wrinkles and cracks.
- Paintings that are completely covered by different acrylic paints.
Category-3 Paintings covered by glass has following sub-categories and degrees of damage:-
- Paintings showing very fine pattern of crack which is not visible from a
- Paintings showing heavy flaking
- Paintings showing heavy flaking which is roughly retouched or over-painted in part.
Some Paintings covered with glass look in good condition, but a closer examination is required to know the hidden damage. Trapped moisture has caused flaking.
This flaking is extremely heavy in certain areas and adding more to this problem is previous retouching by inappropriate material.
Wet-cleaning Tests Performed on Category 1
- The areas with lesser grime were tested with ethanol and distilled water mixture (1:1) and results were good as seen in the following pictures:
- There were some areas where grime was much thicker and ethanol, acetone and other solvents and their mixtures could not help much. Treating with ethanol first and then with more volatile solvent improved the cleaning results, but the action was not only very slow, it was also showing blanching. It was anticipated that surface cleaning would require a modified water-based system.
- Results got better with increasing the pH slightly and including a surfactant in the formulation.We used Triethanol amine(TEA) as it is a week base and it neutralizes fatty acids, adjusts and buffers the pH, and solubilises oils and other ingredients that are not completely soluble in water.Triethanolamine is used primarily as an emulsifier and surfactant. TEA has also shown good results in removing stubborn grime. We formulated a solution keeping in mind the problem of residue that surfactants might create if used in higher concentrations. We calculated an ideal formulation understanding well the cleansing action of micelle formation and the critical micelle concentration (CMC).
Detergency occurs when a critical amount of a surfactant in solution is reached and the surfactant molecules group into micelles2. In an aqueous solution, the surfactant molecules orient themselves with their fatty ends to the inside and the water soluble ends to the outside of the micelles. Micelles can form around fatty, non-polar material and aid its being carried away in water. The concentration where micelles just begin to form is termed the critical micelle concentration. When formulating a detergent, we want to have surfactant present in excess of the CMC, so it can carry grime away, but not too much of an excess because that will have a tendency to leave excess detergent behind, complicating rinsing and clearance.
- The other surfactant we tried in our test formulations is Potassium methyl cyclohexyl oleate3. This surfactant has been used with eminent success on historic and artistic objects.As noted previously, Potassium methyl cyclohexyl oleate is meant to be used in diluted form, mixed either with water or mineral spirits. In general, following concentrations are recommended :
- for aqueous cleaning, from 1:6 parts by volume (~14%) or 1:7 (12.5%) to 1:10 (9%) dilution with water, and
- for non-aqueous cleaning, 1:10 (~9%) to 1:20 (~ 5%) in solvent (mineral spirits).As far as clearance (removal of any residues) is concerned, it is advised to use the same solvent as is used as diluent: that is application of white spirit for clearance of non-aqueous solutions and water for clearance of aqueous solutions.We tried even more dilute solutions. We started from 1% and were finding 3% -5% as good to work with. We even used ethanol before using Potassium methyl cyclohexyl oleate, to enhance the effect without increasing the percentage