Preserving historic paintings

What if you need to protect old, precious artwork. How can you learn more about it, and keep it safe, without damaging it? Chris Smith spoke to Paola Ricciardi, a scientist at the Fitzwilliam Museum in Cambridge who is researching non-invasive ways to study artefacts...

Paola - Well the first thing we do is we take a really good look at it and we use a range of imaging and spectroscopic methods to figure out for example, who painted something, how did they paint it and where did they get the materials that they used? Who commissioned artwork? Why did they commission it, when was it commissioned? What's the context behind artwork? We do a lot of forensic science I guess you could say.

Chris - It’s like a postmortem for a painting.

Paola - Absolutely. That's exactly what we do.

Chris - But someone hands you a picture and you can tell all that just from the picture?

Paola - Well you have to take it to the lab and you have to use quite a different range of light methods. So we use x-rays, use infrared light, UV light, visible light and with that range of different spectroscopic methods you can actually figure out lots of things about, you know, a painting. Just to give an example, if we use infrared light, take an image of the painting, usually you can see what's underneath and what is underneath could be a sketch that artist made before he painted the object. And different artists usually have different drawing styles. And so that's a really good way to distinguish for example between the work of different artists even if it's not immediately apparent from the painting itself.

Chris - Is the key the non-destructive aspect of this that you're using light to interrogate the surface, and the light just bounces pretty much harmlessly off but there's information written into that light that's coming back and that gives you the clues as to what's in there.

Paola - Exactly yes. We exploit different ways that light interacts with matter so it can backscatter you know it can bounce off in different ways as you said. And those different ways means we can detect whatever light comes back to our instruments.

Chris - So that tells you the sort of chemical imprint or fingerprint that's in the pigments that the artist used, so you can get a chemical signature almost.

Paola - Exactly. Yes. So some methods such as Raman spectroscopy, which has nothing to do with noodles but more to do with an Indian scientists, who actually discovered the effect.

Chris - So Indian rather than Chinese or Japanese?

Paola -  Yes. Mr. Raman was an Indian scientist who discovered the Raman effect. So what that does is it gives you the molecular fingerprint of your pigment in this case. It identifies exactly what kind of material you're looking at.

Chris - And presumably different people who went to art school at different times in history would have worked with a specific or fairly unique palette, that would have been unique to them as a painter but also the era in which they were working. Is that a reasonable deduction?

Paola - It's a really good point but unfortunately for most of history the palette is pretty much the same.

Chris - So what works works, so go on using it.

Paola - Yes exactly. It's only in the late 18th, early 19th century that we start seeing different pigments coming up and that's actually detecting those pigments in historic old master paintings for example, is a really good way to test if someone’s done something to them.

Chris - Yeah. Do you also get to understand how time affects those pigments, because one of the keys is,you know,if we're looking at a picture it is 500 years old that's had a lot of time on the wall it's had a lot of light and sunlight bleaching, it has had oxidation, people used to smoke a lot these things and Elizabethans were notorious weren’t they. You used to get these enormous pipes and things there would've been clouds of smoke going everywhere. So can you begin to see how those pigments have changed over time, how they've chemically interacted with the environment they've been in and therefore a) how to predict what it would have looked like that picture and b) how to put it right.

Paola - Yes. Yes that's exactly what we do and that's why we work so much in collaboration with conservators, thus to protect and you know stabilise and conserve these objects for the future. So we try and detect various types of degradation for example that you might see on a painting and figure out whether we can stop that. We don't usually want to reverse it or it's not always possible to reverse that. You don't usually want a painting today to look like it hasn't had any history you know it is a 500 old object you're supposed to look 500 years old.

Chris - Someone did say to me that you know part of the art is that it continues to evolve and change.So it would be a bit wrong for us to intervene in that natural aging process which would be robbing something away from the art to wind time back but. But can you do it digitally if you take a picture of that and you understand how the image has been changing over time chemically. Can you ask the computer, well wind the clock back wherever you see these different pigments being used and put them to how they would have been.

Paola - Absolutely in fact a team at the Getty Museum has done exactly that and they did that comparing a painting which had aged and darkened over time, with a manuscript illumination painted by the same artist because the manuscript has been closed in a book for 500 years. And so it hasn't aged, hasn't been exposed to light and smoke and other degrading agents. So they took that color and so digitally manipulated a painting to make it look like that.

Chris - And are you shocked as it look does it look strikingly different?

Paola - It absolutely does, it's very different and it's amazing actually.

Chris - So all there instances where you would want to intervene because I've heard it said by various chemists and things that you do end up with various chemicals that can be destructive to a painting and actually you do need to intervene and stop things. So are there ways to do that? And can you do it in a way that is sympathetic to the art.

Paola - Absolutely. Conservators nowadays would intervene on a painting if someone in the past intervened in a non-sympathetic way. And then you want to remove that previous intervention and make sure that you preserve the paint.

Chris - Well that's true because of course techniques that they would have had a hundred years ago are nothing like, not a patch on what you’ve got today.So you spend loads of your time unpicking people's best attempts and best intentions. And have they ruined it for everybody or can you get get that off?

Paola - It depends. Sometimes they have. Sometimes you can't get it back but not always.

Chris - So what happens then if you come along you touch up a piece of art and make it look nice and stop the clock on it. And then I take it to a gallery and they say it's a forgery because look there's all these pigments that shouldn't be in there in there.

Paola - Well what we do today usually is use pigments and materials that are actually compatible with the history of the painting. And we also document everything that we do.