Sunday, March 27, 2011

Stinky old things can be treated

"Lorraine Gibson: How the smell of decay can help save relics"

Chemist Lorraine Gibson is working on technology to analyse the condition of old books and treasures by the gases they emit


Robin McKie

March 27th, 2011

The Observer

Walk into a library or museum and you cannot fail to note a distinctive musty smell. This is made up of a cocktail of compounds given off by ancient tomes and exhibits. For some the experience is pleasant; for others, such smells are fusty. But for chemist Dr Lorraine Gibson, of Strathclyde University, these odours are the bread and butter of her research.

Gibson believes smells can be used to expose the condition of a book or an artefact – without touching it – before it has decayed dangerously, so repairs and restoration can be applied early to avoid serious damage later on. The trick, she says, is to develop a device than could mimic our sense of smell, or at least part of it. This is the focus of her work at Strathclyde University's department of chemistry.

So how can smell help the heritage business?

The smell produced by an old book or museum exhibit is comprised of hundreds of volatile compounds. Most of these will be of no interest but a few will be of great importance. We are trying to pinpoint the important ones so we can discard the rest. Consider paper. It is comprised of cellulose, lignin and many other compounds. As paper ages, it changes – anyone who works with old books knows it becomes brittle and fragile. Volatile byproducts are given off. We want to use these as an indicator of a book's condition.

"Volatile" suggests the book is about to explode.

Volatile just means a substance that easily converts into a gaseous state. In other words, a chemical that is emitted from the paper, into the air. And it is not just old books that do that. Many objects in contemporary art are made of polymers and plastic. These are not immortal, they degrade, and as they do so, they give off chemical markers that we want to detect. In other words, we are trying to create heritage smell-detectors for paper, plastic and polymers.

In the case of paper, the type that is most at risk is the paper made between 1850 and 1950. The manufacturing process had a lot of acid in it and the acid exacerbates decay. And ink can also be a problem. Iron gall ink can attack paper badly because of the acid that was used in its manufacture.

We are also working with materials like cellulose nitrate and cellulose acetate, which are contained in archaic film material. So we are working on a case study of photographic materials with the National Archives of Scotland. We want to know how stable they are.

It sounds like the device McCoy uses in Star Trek to determine patients' health…

The comparison is not that far-fetched. The food industry has already developed chemical sensors that can tell when a piece of meat is going off by analysing the gases it gives off. These devices can detect gases at much lower concentration than a human nose. Getting sensors to measure a signal is just one part of the operation, however. It's getting sensors to measure the correct components of a smell, the two or three volatiles that tell us something special about the object, and at low concentration, that is going to be tricky. If we sample the air in a room, there will be hundreds of components but only four or five of them will tell you what you want to know about an object in a cupboard in that room. It will be like a fingerprint that will tell you if something is going wrong.

How far have you got with the project?

We have started working with commercial sensors, like those in the meat industry, and we are modifying them. We are not trying to reinvent the wheel. The technology exists and we hope to have developed a prototype within three years. Commercialisation will be the next step. The key thing is the device will be portable. You can't bring vintage cars or an old plane into a laboratory. We have to go where the collections are – like the National Museum of Flight in East Lothian. Is the plastic in the seats degrading? We will be able to tell.

What is your detection limit?

We are working on an instrument that could spot chemicals at a dilution of one molecule in a billion. That would be like trying to detect a single Scotsman in the middle of China. Current chemical sensors only have to work at a sensitivity of one molecule in a million. So we are going to have to improve matters by a thousand.

There are various different types of sensor that we can use. For example resistance detectors, which are activated when a molecule touches them and changes resistance in an electric current. We will also look mass spectrometry devices which will allow us to determine chemical components at very low concentration and which are being pushed in homeland security research as explosive detectors.

Certainly there will be clear industrial applications from this work. These will be our medium- to long-term goals. These are going to be non-invasive devices so who knows what applications they could have: medical diagnostics, for example. Then you really would have caught up with McCoy in Star Trek.

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