This small landscape has been painted on tinplate. Metal is one of the very oldest supports for oil painting, and tinplate has been used for centuries. Characterised by its smooth and rigid surface, the tin support has allowed this artist to execute finely detailed brushwork. As the metal material is non-absorbent, the paint has been thinly applied with the artist taking advantage of the vibrancy and intensity that the tin support lends to the colours.
The style of the painting sits firmly within the Romantic lexicon in which artists depicted landscapes that evoked the imbalance between the awesomeness of nature and the smallness of man. In this work, the figures look out at a grand vista that dwarfs them in its majesty. The depiction of nature is intended to stir the viewer’s emotions and to promote the theme of contemplation. Romanticism celebrated the pastoral idyll – invoked in this work by the goatherd and his flock.
The painting is framed. The surface is discoloured by a heavy and degraded varnish. There are areas where the paint layer is missing, and scratches in the lower half of the painting in the darker foliage. In raking light the thinness of the paint layer is evident, and in UV light the green hue indicates that a damar varnish was probably used. There are also small areas of retouching evident in the darker patches seen in the examination under UV light.
Tin was not a common support for the Romantics who were painting between the 18th and 19th centuries. However, it was a medium that painters of folk art turned to in the 19th century, suggesting that this landscape in the style of Caspar David Friedrich may have been painted in the later stages of the Romantic period.
In the areas where mechanical damage has occurred, disrupting the stable oxidised layer of tin, corrosion of the core metal is clear. This has probably been caused by exposure to moisture and oxygen in the presence of iron. Tin plated iron was widely used by painters in the 19th century. The dull grey and white colour of the tin indicates exposure to high humidity which causes the oxidised layer of tin to discolour.
Examination of Painting with Ultraviolet Light
By examining the painting surface with ultraviolet light, it is possible to see the extensive coverage of the varnish layer. It also appears that there is retouching present in the foliage along the lower edge of the painting and in the overcoats of the two figures that are depicted from the rear as they gaze at the vista.
Like copper and other metal supports, tin is a stable support so, even though thinly painted, the paint layer is in relatively good condition. There are no obvious ageing cracks, although there is evident corrosion that has left irregularly scattered patches of paint layer loss across the surface.
These crater-like deformations indicate that the painting was probably exposed to atmospheric moisture in the form of high humidity or other atmospheric pollutants. Tin is an alloy that usually includes iron. In this case the rust patches indicate the presence of iron in the tin support which has combined with oxygen from the damp to form iron oxide and iron hydroxide.
Surface Cleaning
I conducted a series of tests to determine what solution would clean without damaging the paint layer. A metal support is less adhesive than a canvas so it was important to avoid swelling the paint layer too much with any aqueous solutions.
| Deionised water | No effect |
| Ordinary water | No effect |
| Citric acid + water pH6 | No effect |
| Citric acid + EDTA + water pH6 | No effect |
| Triammonium citrate 10% | Slight grey grime lifted |
| Surfactant + EDTA + buffer + water | No effect |
| pH Neutral soap | No effect |
| Strong alkaline soap + water | Black grime lifted |
| Alcohol + gelled emulsion + water | Discoloured varnish lifted but also some paint removed |
| Benzyl alcohol + gelled emulsion + DPTA + water | Discoloured varnish lifted and paint layer remained undamaged |
Using TAC 10%, I cleaned the surface of the painting, removing dirt and grime. Although the swabs appeared to be soiled, suggesting that a layer of dirt was removed, it was hard to see much difference because of the very yellowed varnish layer.
Using a non-acidic and highly alkaline cleaning agent based on potassium methyl cyclohexyl oleate dissolved in water, I was able to remove a deeper layer of grime. The swabs were much blacker. Again, though, the effect was minimised by the presence of the yellowed varnish layer.
The effect of the cleaning solution is clearly visible here, with the cleaned area on the left and the uncleaned area on the right.
To tackle the ageing varnish layer, I introduced a solvent solution. Initially, I tried alcohol diluted with water and a gelled emulsion. This had a dramatic effect on the varnish and removed it. However, it also removed some of the paint so I needed to try something
less aggressive.
Next I tried the reagent benzyl alcohol in a gelled emulsion to remove the extremely stubborn aged varnish. I added 4 drops of benzyl at a time to the gel and cleared it with deionised water mixed with a buffer to match the solvent’s pH level of 8.5.
I added a chelator (DPTA) to the mix – the chelator binds to the metal ions in the dirt and allows them to be lifted. With a concentration of 24 drops of benzyl added to 1g DPTA, gel, and 1ml deionised water, I achieved a result that removed the varnish layer without damaging the paint as long as the solution was thoroughly cleared.
Retouching & Varnishing
The paint layer is so thin that I would not have been able to fill the areas that are missing paint in a way that would match the surface. By taking advantage of the thick consistency of gouache to retouch these areas instead of watercolours, I was able to sufficiently fill the craters.
I think varnished the painting with damar and finished off the retouching of the surface scratches and blemishes with conservation colours.