Poison, stray fingerprints, microfossils of ancient bugs – conservators at the National Gallery in Dublin using modern scientific techniques, unearth surprises as well as information about the methods and materials of great artists, writes JOANNE HUNT
HIGH IN the eaves of the National Gallery of Ireland, up hidden stairways and away from the bustle of visitors below, science is uncovering the secrets of some of painting’s great masters.
Shadowy figures the artist wanted to hide, pigments made from poison, and secret fingerprints are all revealed when centuries-old artworks meet modern scientific methods.
While a few decades ago, much restoration and preservation work was done by artists using best guesses as to original materials, modern-day conservators are more likely to have a grounding in chemistry and physics for a role that’s equal parts art historian, artist, sleuth and scientist.
“It’s one of the exciting parts of conservation that you can step back in time and understand exactly what a 17th-century Spanish master was using in his studio in Seville,” says Muirne Lydon of her role as a paintings conservator at the gallery.
With works from the 15th to the 21st century in its charge, the gallery employs six full-time conservators and two specialist photographers. Their work ensures these priceless works pass to future generations in the best possible state.
“In the museum, we’re mainly dealing with age,” says Lydon of the challenges. Whether it’s the natural degradation of hundreds- of-years-old paint and canvas, or the effects of poor storage or cruder restoration work earlier in the painting’s life, the team has its work cut out for it.
In the bright and peaceful gallery attic, interrupted only by the squawk of seagulls outside, Lydon is working on 17th-century canvasses that tell the story of the prodigal son by Spanish artist Murillo, on whose conservation she collaborates closely with the Prado museum in Madrid.
A crucial step to conserving the paintings is understanding the artist’s materials. Cross-section analysis helps to solve the centuries-old puzzle. “We take tiny, tiny samples to get a cross-section of the paint layer,” explains Lydon. “This allows us to see right through the centre of the composition.”
Looking at the sample through a binocular microscope she can see “how thick the varnish layer is, what type of layer structure the artist is using, what type of colours and right down to the ground layer”.
A degradation of something like animal glue in this hidden ground layer can cause the paint to flake over time, while the top varnish layer can oxidise and yellow.
In its conservation, the gallery strives to be sympathetic to these original materials. “We’re quite conscious of that and of changing the infrastructure or composition of the actual work,” says Lydon.
While sampling can diagnose issues deep in the painting, gas chromatography and mass spectrometry are used to confirm the organic chemistry of pigments, providing a map for their conservation.
“So we can tell from elemental analysis whether the painting has high lead points or high cobalt points that might be a cobalt blue or a lead white,” explains Lydon.
Analysis also divulges that artists themselves were no slouches at chemistry. A sky in one of the Morillo’s shows the artist used a pigment of smalt blue, a ground glass containing cobalt.
Aware of how it discoloured and darkened with time, Morillo mixed it with lead white to retard its dulling. As smalt was a cheaper material, he used it as a bulking agent, only adding the more expensive azurite or lapis lazuli blues in small amounts.
“It’s a very privileged position,” says Lydon. “With this type of analysis, you could literally be sitting beside the artist while they are painting.”
Chemical analysis can also reveal a curious and sometimes-poisonous palette of everything from an emerald green containing arsenic to mercury reds, lead whites and even egg yolk. But science also shines a light on the artist’s style.
“Murillo was quite a fast painter, an economic painter, he really knew his materials,” says Lydon.
“It’s the cross-sections that are complicated with multi-layers that you look at and think, maybe wasn’t so aware or so assured of his materials.”
And from analysis of the materials of the artist comes a window into his mind. With another of the gallery’s Morillos, The Prodigal Son Feeding Swine, X-rays and infrared reflectograms have uncovered a painting within the painting.
Painting a large ruin in his original conception of the piece, the artist later painted it out. Carefully obscuring it with sky, he wasn’t to know that his secret would be uncovered by science in a Dublin gallery more than three centuries later.
“I think probably what happened was Morillo decided that maybe the scene wasn’t desolate enough with this ruin in it so he decided to paint over it and create this much sadder, and more lonely composition,” says Lydon of the discovery.
“This kind of forensic examination is quite privileged information to get,” she says. “We’re not just seeing the final painting, we’re also understanding the whole process the artist has gone through to arrive at that finished piece.”
Not all of the imprints discovered are so intentional however. Through the looking glass of science, the gallery has not only found an accidental fingerprint of William Hogarth on his 1747 Portrait of the Mackinen Children but far more curious things too.
Analysis of the calcium carbonate, pyrite and animal glue ground layer used in Dutch paintings has uncovered the microfossils of ancient bugs. The appearance of fossils in Spanish paintings analysed by the gallery however was even more surprising, disclosing a trade route in artists’ materials between Holland and Seville.
But the gallery’s science is not for science’s sake.
“Our main priority is the care of the collection for the public today and for future generations,” says Lydon. “It’s an ongoing story and we’re just here for this part of the journey.”
Laser and X-ray reveal the real secrets of Kells
HAVING survived some rough handling over centuries of raids, the
Book of Kells, the splendidly illustrated Latin gospels, now rests safely in Trinity's Old Library.
While bandits made off with the book in 1007, stripping it of its gold cover, its present guardians are slow to even touch it. This makes finding out more about the materials used by its monk-illustrators all the more challenging.
"The thing with our analysis is that it all has to be non-sample based," explains Susie Bioletti, keeper of conservation at the college. "So we use techniques that ensure we're not in contact with the surface and won't cause any damage."
Micro-Raman spectroscopy is one such technique. "It uses a little laser that shines on the material," explains Bioletti. "It looks at the energy given off and that gives you a little signature of the type of material you've got."
X-ray florescent technology is also used, where X-ray energy looks at the signal coming back from the page to give clues as to the elemental details of pigments. It is expertise Trinity's preservation and conservation department has shared with the National Gallery, helping it, among other things, to identify the palette used by artist William Turner in his watercolours.
Dust is a problem for the Old Library's conservators. It's the silent enemy of the 200,000 books on the shelves. A PhD student is now studying where the dust is coming from and how to limit its impact. Stabilising the iron gall inks of the 1641 depositions – pages that record experiences following the rebellion by the Catholic Irish – has been another challenge for Bioletti and the college scientists with whom she works.
As it oxidises with age, the iron ink "kind of bleeds, so instead of having a nice tidy letter you have a kind of fuzzy fat letter," explains Bioletti.
Every page of the depositions' 32 volumes was treated individually, from submersing them in ink-stabilising baths to repairing tears and strengthening pages. The restoration is now complete.
Their preservation has meant the pages could be imaged, too, and now, more than 350 years later, they are available on the internet.
"It's fantastically interesting work, but the collections belong to everyone," says Biloetti. "Conservation just aims to make sure the works are available for everybody – to think about, to enjoy and to learn from."