Conserving the Painting 

The conservation of Chevalier's Cook Straits was executed by Carolina Izzo, Conservator of Paintings, who also authored this article.

1. Conservation and restoration work on Cook Straits took several months. It involved consultation with scientists, curators and a radiologist.

Carolina Izzo, Conservator of Paintings, during the conservation work on Cook Straits by Nicholas Chevalier

2. The conservation work was divided into four stages: condition assessment, scientific analysis, conservation treatment, and digital documentation.


In the course of the condition assessment, a pencil drawing of the canoes emerged on a detail of the X-Ray.
X-Rays courtesy of Pacific Radiology.

Detail of the back of the painting – the linen and the stretcher are evident.

3. During the painting’s assessment, details of the artist’s processes were revealed but also evidence of damage which had occurred over time or was caused by previous conservation treatments.

Scientific analysis revealed useful information which was used to determine the conservation treatment.

Carolina Izzo, Conservator of Paintings, during the conservation work on Cook Straits by Nicholas Chevalier

Details of the surface clean to the rear of the painting.

4. The treatment to the back of the painting was primarily of a structural nature. It involved cleaning the back side of the canvas; consolidating the auxiliary support (stretcher) and adhering the tacking edges. Missing or broken keys were replaced.

Carolina Izzo, Conservator of Paintings, during the conservation work on Cook Straits by Nicholas Chevalier

5. Cleaning the surface of the painting involved removing the yellowed varnish as well as the discoloured areas where chips of paint had been replaced. Analysis of the varnish revealed that it was Dammar, a natural resin which contained dark pigmentation probably added to change its hue. The varnish was carefully removed using cotton swabs soaked in a solvent mixture which dissolved it without affecting the original paint surface.

6. In natural light it was possible to see the discoloured areas of retouching which covered the cracked area of the sky.

Carolina Izzo, Conservator of Paintings, during the conservation work on Cook Straits by Nicholas Chevalier

7. Under the UV light the discolored fillings become visible.


Detail of retouching from a previous conservation treatment(left) and the same area viewed under UV light (right).

8. After the removal of the varnish, a 300 millimetre long tear in the canvas became visible – see area above to the left of the island and across the sea. This explained why the painting had previously been relined.


9 Some areas which had previously been retouched were difficult to remove especially those which filled paint losses. This was finally achieved with the use of specially prepared solutions.

This X-ray shows the actual size of the paint loss which was beneath the round area of retouching. This earlier treatment proved to be irreversible.


Details of the paint layer before (left) and after (right) the removal of the old fill. Drying cracks show the condition of the paint layer.

Detail of the artist’s signature on the front of the painting after the surface clean.

10. Once the surface clean was completed, the conservation work began. Paint losses were filled with gesso and protein glue.

Detail of a paint loss that would be filled.


11. It was decided not to remove some areas of the fill which had been applied in the repair of the tear.(left) This would avoid compromising the stability of the original paint layer. X-rays also provided information about previous paint losses.(right)

Carolina Izzo, Conservator of Paintings, during the conservation work on Cook Straits by Nicholas Chevalier

Detail showing the retouching of areas of fill using paint made specifically for restoration work. Retouching combines a careful and methodical application of this paint with knowledge of colour matching and the artist’s brush technique. It is usually confined to areas of paint loss. This is a reversible treatment.

12. In the final step of the treatment, colourless varnish was applied to the surface of the painting to achieve a uniform gloss, protect the overall paint surface and the new treatments.

Matthew [sic] O'Reilly, Framer of Paintings and Carolina Izzo, Conservator of Paintings, deciding on the appropriate patina hue for the frame.

13. When both the frame and the painting were ready, the framer and the painting conservator consulted to decide on the appropriate patina hue for the frame. This would reduce the visual between the painting and the frame and allow the work to be viewed without distraction.

Matthew [sic] O'Reilly, Framer of Paintings and Carolina Izzo, Conservator of Paintings, applying the patina to the frame.

14. The competed work.


Scientific analysis:
In this context, this encompasses the systematic study of the structure and behaviour of the physical object during its life time. The surface of the painting is examined and analysed in sections with a microscope and an Infrared light. The information gained allows the conservator to make decisions about the level of intervention required forthe treatment.

X-ray radiography is a form of high-energy electromagnetic radiation that travels like ordinary light but can penetrate most objects. X-raying works of art can reveal losses of paint, previous conservation treatments and methods of construction that might not be visible to the naked eye.

Stretcher: A supporting frame upon which an artist’s canvas is attached and stretched. Usually made of wood, it can be reinforced by crossbars. The first expandable stretcher appeared in the 18th century.

Tacking edges are the edges of the canvas which attach to the stretcher by means of staples or tacks. These are usually seen on the back of the painting especially when the artist likes to paint the outer edges of the unframed painting.

Keys: Common name for the triangular wooden elements inserted into the corners of the stretcher to ensure that the canvas remains tightly stretched. Today many types of keys including metal bolts and springs are available.

Dammar is a natural soft resin made of triterpenoid compounds extracted from the Dipterocarpaceae family of trees found in the Seychelles Islands, New Guinea and the Philippines and made into varnish. First recorded use of Dammar as a picture varnish is dated around 1829. It came into wider use about 15 years later.

Fill is the material usually a mixture of gesso and adhesive, used to plug areas of paint loss in a painting’s surface.

Ultraviolet light is invisible to the naked eye however its scientific applications make it a very useful tool for conservators. Raking the surface of a painting with ultraviolet light can reveal repairs, areas of over-painting, tears in the canvas etc. UV light can only be used in this way for a short time as longer exposure may cause irreversible damage.

Formerly the conservation of historic paintings often included ‘relining’ the original canvas. This involved the application of a new piece of canvas to the back of the original and would be undertaken in situations of traumatic damage such as tears or holes.
A mixture of bees wax and resin or a water based paste (starch) was commonly used to stick the canvases together. Heated irons would then be used to press the two canvases together. This treatment not only reinforced the canvas but also consolidated any loose paint.
Today, this practise of relining is generally avoided as the treatment has a strong impact on the whole surface and in most of cases is considered an irreversible treatment. Today, a thread by thread consolidation of the canvas is considered more effective to ensure a non-invasive, reversible treatment.

Retouching refers to a conservation technique that fills the gaps or losses in the surface paint with different media than the original.
There are various retouching techniques which colour the material used to fill losses. The overall aesthetic effect for the viewer and the characteristics of the materials used are among considerations about which technique to use. Retouching is not always necessary but can complete the visual continuity of a painting. In cases where the original colour or other details of the paint loss are not known, neutral tones are applied to the loss to balance the optical view. Sometimes it is thought best to leave the loss unfilled.
Historically retouching methods have varied. As can be seen in some of the photographs, previous areas of retouching here have exceeded the actual size of the paint loss perhaps to integrate it better into the overall painting. However over time these areas have discoloured and do the reverse of what was intended.

Reversible treatment: This refers to a principal of contemporary conservation techniques. It describes the aim that all treatments are reversible – that after a long period of time, the materials used can be removed to return the object to its original condition. It allows for the possibility that if a better conservation process or technology is discovered in the future, the treatment undertaken can be removed or reversed with no further damage.

Patina: is the gloss on the surface of woodwork produced by age but which can also be produced artificially in the gilding process. In marble, it is the natural aging of the surface over many years. In paintings, it can be artificially achieved with a thin layer of natural pigments that gives the new surface a feeling of age.