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Aboriginal and Torres Strait Islander Cultural Material
Care of bark paintings
The bark most commonly used for paintings is called Stringybark—Eucalyptus tetrodonta. The pigments used in the paintings are natural red and yellow ochres as well as white gypsum and charcoal. Since the 1960s these pigments have been mixed with water and varying quantities of PVA glue, generally the brand name Aquadhere. Earlier, artists used vegetable binders with the pigments, including orchid juice, the sap of certain leaves and trees and turtle egg yolk.
Problems encountered with bark paintings
Loss of paint
Possible Causes
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Poor storage conditions.
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Poor mounting systems.
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Too little binder in the paint.
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Paint applied over unbound pigment.
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Environmental fluctuations cause movement of barks, causing paint to flake.
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Some paints shrinking more than others as the paint dries.
Preventive Action
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Store bark paintings flat, painted side up, and in a stable, dust-free environment.
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Support barks so that they are protected against vibration.
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Avoid stacking objects one against the other.
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Seek the advice of a conservator.
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In communities where the artist is available to retouch his or her work, take great care to make sure only the damaged area is treated and pigment colours are matched
| CAUTION: |
| It is unwise to spray commercial fixatives onto flaking or powdery areas, because the fixatives often yellow in time, and the pressure of the spray can blow flakes from the objects. |
Mould growth
Possible Causes
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Relative humidity above 65%. The main storage room may be at a low relative humidity; but pockets of higher relative humidity can occur, especially in badly ventilated corners and drawers.
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Mould can grow unseen on the back of a bark where the relative humidity is higher because of poor storage conditions. The mould can then grow through fine cracks in the bark to the painted surface.
Preventive Action
- Store or exhibit in a well-aired environment with relative humidity below 65% and preferably below 60%.
Splitting and curling
Possible causes
- Rapid fluctuations in relative humidity-fibres absorb and lose water, which causes barks to expand and shrink.
Preventive action
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Store the bark horizontally and well supported in a stable environment.
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Avoid placing the bark near heaters, air conditioning outlets or open windows. The environment is not likely to be stable in these areas.
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The most stable areas are normally the inner rooms of a building.
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In time, the bark may relax into a flatter position.
Warping
Possible causes
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Normally because of uneven pressure on the bark. It can occur over a long time, and can eventually cause splitting and loss of pigments.
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Can be the result of poor mounting systems, which allow some areas of the bark to move in response to environmental fluctuations while others are kept immobile.
Preventive action
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Remove any uneven pressure from the back or front of the bark.
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Remove, or get a conservator to remove, any glued bars of wood from the back of the bark.
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If you wish to display your bark painting, mount it in such as way that it is supported without being subjected to uneven pressures.
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