Restoring 'Christ Teacheth Humility' by Robert Scott Lauder (part two)

In this three-part blog by Lesley Stevenson, Senior Conservator at the National Galleries of Scotland, we will be following the conservation processes involved in restoring 'Christ Teacheth Humility' by Robert Scott Lauder. 

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In part one this painting and its fascinating history as one of the Scottish National Gallery’s earliest acquisitions were introduced. I would now like to describe the conservation processes currently underway in an eerily empty large gallery in the Royal Scottish Academy building.

The temporary studio set up in an empty gallery space.

Documentation, both written and photographic, is an important aspect of any conservation project and this is carried out at every stage of the painting’s treatment. Just as we benefit from information left by our predecessors in the National Galleries of Scotland’s Conservation Department, we have a responsibility to inform future custodians of the collection. Such information is gathered in a systematic manner and details both the structure and condition of each element, in addition to describing materials used and thinking behind any of the conservation processes.

The first phase in any treatment usually involves the removal of surface dirt with either a dry dusting brush or the use of controlled moisture, in this case, deionised water. This offers a good opportunity to scrutinise the paint surface at close quarters. Varnish solubility trials then follow to assess the efficacy of a range of solutions. Several differently pigmented areas are tested in order to devise a suitable, that is, safe and controllable method for removing the discoloured varnish. In this painting we have a combination of a synthetic coating (applied in 1983) above much older layers of a natural resin varnish (such as dammar or mastic) probably applied earlier in the twentieth century. The latter appear to be uneven in both distribution and level of discolouration. Evidence suggests that the painting was selectively or partially cleaned in the past. The lighter areas, for example, the figures’ faces and hands as well as some draperies, have been more thoroughly cleaned than the darker background. This would have been a quick way of effecting a significant although likely temporary, improvement in the painting’s overall appearance. Such a tactic is not surprising for a work of this size.

Conservator Lesley carrying out varnish removal.
The cotton swab reveals how discoloured the varnish is.

Why is a varnish required in the first place? For a darkly coloured, mid-nineteenth-century painting this layer provides both saturation and protection of the surface. By ‘saturation’ essentially, we mean an effect similar to the difference in appearance between a dry and wet pavement. The varnish allows the original range of colours applied by the artist to be seen clearly. However, inevitably with time this surface coating naturally degrades. Exposed to the environment varnish becomes yellow, can imbibe dirt and often loses its original transparency.  Instead of enhancing the original colours, as it ages a varnish can obscure and distort, become cloudy and opaque. It then impedes our appreciation of the original brushwork. In summary, light areas can darken and dark areas can lighten as the varnish can develop a bloom as it breaks down.

A detail from the sky showing the cleaned area on right with discoloured varnish still visible on left.
A detail from the centre foreground showing the cleaned area on left with discoloured varnish still visible on right side.

The selective cleaning carried out previously on Christ Teacheth Humility may have been prompted by reasons other than expediency. Darker paint layers are generally more difficult to clean safely than those containing lighter pigment mixtures as traditionally these are more sensitive to solvents. In part this is related to the pigment to medium ratio as darker pigments usually require more oil to make a workable paint. (Oil is the medium or carrier for the coloured pigment and this is the part of the matrix most easily affected by cleaning solvents). As some British artists were notoriously experimental during this period, another consideration is the possibility of the artist deliberately adding unstable materials to his or her paint. Inspired by a desire to emulate the deeply saturated hues of the Old Masters, such as Rembrandt and Titian, many artists incorporated substances such as varnish resins, wax or bitumen (a coal tar derivative) to their paint, often with catastrophic results. Such additions would inhibit the drying of the oil and could also cause cracking to develop, often shortly after painting. From the conservator’s perspective, critically such additions would also result in the paint being soluble in the same solvent solutions used to remove a discoloured varnish.

Watch Lesley remove the discoloured varnish (blog continues below)

Finally, it is worth noting that another issue with nineteenth-century paintings is the potential adulteration of or tampering with materials by the artists’ colourmen (suppliers of artists’ materials), a practice mentioned in artists’ literature, such as the widely available and popular instruction manuals of the time. Unbeknown to the customer, unscrupulous colourmen may have added cheap, unsound and / or unsuitable quantities of materials such as extenders and driers to their paints which could also influence their behaviour. 

Thankfully, we have little evidence of these phenomena here and Scott Lauder appears to have employed a reliable technique. He later became a highly influential teacher so evidence suggests he took his craft very seriously. We do have small areas of drying cracks and these relate to minor compositional adjustments the artist has made while painting. For example, there is distinctive drying craquelure around this figure on the left side suggesting the artist has altered the line of his shoulder. It is likely that Scott Lauder has not waited for the underlying layer to dry properly before applying a layer on top and these round-edged cracks have developed as the upper paint layer contracted on drying.

Detail of characteristic drying cracks at shoulder of man on left.
A detail of figures on left hand side during cleaning.

Varnish removal with solutions of standard organic hydrocarbon solvents is progressing well and has already produced a marked improvement in the painting’s appearance. For a picture of this age and size the paint layers are in remarkably good condition with past restoration primarily restricted to minor areas of paint loss or abrasion from past accidental damage.  

Once the cleaning is complete a new, what we term ‘isolating’ layer of varnish will be applied by brush using a synthetic resin devised specifically for this purpose. Unlike its predecessors, this layer will not yellow and should remain soluble in very mild solvents for many years to come. Importantly, this modern varnish has also been developed to replicate as far as possible, the important aesthetic qualities of natural resin varnish.  

Restoration (or ‘inpainting’) during which areas of damage or abrasion to the paint layer are concealed or made less visible by the conservator’s judicious application of ‘paint’, constitutes the next stage of the treatment. This process of adding rather than subtracting, pulls the whole thing together. Again, a modern, stable, non-yellowing retouching medium specifically designed for this purpose is used, one chemically distinct from the artist’s original oil paint and one that can be easily removed in the future. While we accept that the impact of time can never be reversed, the intention is to allow the original composition to be enjoyed without the distraction of small damages or the subtle muddying veil cast by a discoloured varnish.

It is hoped that once the conservator has hung up her apron and this monumental painting returns to public display for the first time in many years, the viewer will not be aware of the many weeks of concentrated activity on the paint surface. Ideally, the energetic brushwork, colourful draperies, interesting headwear and the consummate skill with which these expressive faces have been described will come to the fore and that Scott Lauder himself would be satisfied with the result.

By Lesley Stevenson, 12 January 2021