Prints, pigments & poison

The conservator engages with art at both a macro and micro level and sees the artist’s hand at work in ways often unimaginable to the viewer. The detective work involved in identifying materials and techniques, separating deliberate effect from accidental damage or deterioration often provides new and exciting insights into the images on the Gallery walls.

The typical palette in Ethel Spowers and Eveline Syme's works feature carbon black, yellow and brown ochres, ultramarine, cobalt and cerulean blues, emerald green and two organic lake pigments — alizarin crimson and a distinct lilac. Lake pigments are made by attaching a dye to a base material such as alumina, making a dyestuff into a workable particulate pigment. This process can also extend more expensive dyestuffs, making them cheaper to use. Bound with oil to create printer’s inks, this limited palette was then overprinted to achieve a wider range of colours.

Emerald green commonly recurs throughout the works. A highly toxic vivid green, invented in the 19th century, it was still commercially available until the early 1960s. Many historical pigments are toxic, based on arsenic, mercury and lead.

Today we are increasingly aware of the health and safety issues related to works of art, but this was not always the case. Emerald green belongs to a group of copper acetoarsenate pigments that were extensively used for many household goods including furniture and wallpapers. A similar pigment, Scheele’s green, was used on the wallpaper in Napoleon’s apartments on St Helena and has been suggested as the cause of his death. Large amounts of arsenic (100 times that of a living person) were found on Napoleon’s hair and scalp after he had died. While poisoning theories still abound, it has been confirmed through other medical cases from the period that arsenic dust and fumes would be circulated in damp Victorian rooms sealed tight against the drafts that were thought to promote ill health.

Registration marks, indicative of the making process, are visible in the margins and old mounting hinges are evident on the top edge. It was noted that the same range of pigments was reused during specific periods of production. A sample group of these works therefore provided focus for analysis.

One of the analytical techniques used was polarised light microscopy (PLM), whereby less than a pinhead of sample is taken and dispersed and mounted on a micro-slide. Viewed at upwards of x500 magnification, a digital image from the microscope can be seen on a screen, and a kaleidoscope of crystalline shapes and refracted light and colour captured. From the examination of particle morphology, and with the assistance of an experienced eye, comparative samples and reference literature, an identifiable set of visual characteristics emerges for each pigment. Emerald green has an intense colour and large floret-like particles arranged around a central point.

Analysis has also allowed potentially light sensitive pigments to be identified, meaning mitigating strategies can be used to ensure the preservation of works during their regional tour.

Know My Name: Making it Modern is on display at the National Gallery 5 Aug – 8 Oct 2023.

Spowers & Syme is a National Gallery Touring Exhibition supported by Major Patron David Thomas AM, Visions of Australia, and the Gordon Darling Foundation. Spowers & Syme is a Know My Name project.