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Conserving John Campbell

February 25, 2011

Before treatment: John Campbell Earl of Breadalbane 1696-1782, by Charles Jervas, 1708

In the Conservation Department we’ve been working hard to get all the works ready for display in the new Portrait Gallery. My colleagues have written two blogs about our projects; the first is by Alexandra Gent:

While the Portrait Gallery is closed hundreds of objects for the new displays have been passing through the Conservation Department. I am a Paintings Conservator and have been working with the Conservation Technicians to make sure the paintings are secure in their frames and looking their best. Most of the paintings only need minimal treatment such as removing surface dirt and securing stretcher keys. But I’ve also had the chance to undertake some longer treatments and look at a few artworks more closely.

After treatment: John Campbell Earl of Breadalbane 1696-1782, by Charles Jervas, 1708

One painting that I have treated is a splendid depiction of John Campbell, 3rd Earl of Breadalbane as a child in Highland dress by the artist Charles Jervas. The varnish layer that covered this painting had become yellowed with age. When a varnish layer is discoloured the true colours and textures of the painting can be obscured and it can appear quite flat.

This image shows a test clean on the cuff of the shirt. The light blue patch in the centre of the image is where the varnish has been removed.

To make sure a painting can be cleaned safely small test areas are always cleaned first. When I removed small areas of varnish from John Campbell the little windows gave me an indication of the transformation that would happen.

The distant mountains are revealed against a pale blue sky

Once I had found a safe solvent for removing the varnish I was able to start cleaning larger areas.  This revealed distant mountains against a pale blue sky. It was very rewarding to see such a transformation.

The painting is in excellent condition and once the varnish had been removed hardly any restoration was needed.

This is a paint sample taken from the top edge. There are three visible paint layers including the thick, pink ground. All the paint samples had this pink layer at the bottom. You can see the grains of pigment that have been mixed with oil to make the paint.

While treating the painting I also wanted to find out more about how the artist had made it. I removed a few small, pinhead sized paint samples from near the edges. Even very small samples can provide a huge amount of information about a painting. The samples were set in resin and sanded to reveal a cross-section of the paint layers. The layers of paint are so thin that they can only be seen using a microscope. By examining the samples microscopically I was able to see that the artist had prepared the canvas by painting a thick pinkish layer over the whole surface.

This is an image of the same paint sample at a higher magnification. The picture has been overexposed to show the large Smalt particle more clearly.

I was also able to further analyse two of the paint samples with the help of Conservation Scientist Susanna Kirk from the National Museums of Scotland and my fellow NGS Paintings Conservator Lesley Stevenson. Using a scanning electron microscope and energy dispersive spectrometry (SEM-EDS) we were able to identify two different blue pigments, smalt and azurite. The very large dark, angular particle is smalt which is a pigment made from coloured glass that has been ground to make a powdered pigment.

John Campbell, 3rd Earl of Breadalbane as a child in Highland dress by Charles Jervas is now on show in Portrait of the Nation at the National Gallery Complex until 4th September 2011.

This is an EDS spectra taken from the centre of the large Smalt particle. The peak labelled Si indicated the presence of Silica which is the main component of glass and Co on the right side of the spectra indicates the presence of Colbalt which is what makes the Smalt appear blue.

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