: Conservation

Rock collections in the UK are an asset worth millions of pounds. Many exploration companies drill into the Earth’s crust and extract cores for analysis – often at a cost of around £1,000 per meter of core. These provide the basic information before a commercial case for mining or extraction can be made and form part of the companies’ commercial archives.

Museums also look after collections and many hold large numbers of valuable geological samples. A common misconception is that rocks are stable, they do not decay or get eaten by pests. Which is why fossils, minerals and rocks surely must be easy to look after.

But think of minerals found in caves or mines: not just dark, but also cold and damp. Many hydrated minerals occur here, for example melanterite or halotrichite. Take them out of the mine, put them in a museum store where they are protected and well looked after – and they will dehydrate. Lose water molecules, decay, and are lost.

There are many similar examples. Depending on the mineral species they will take up or lose water molecules, recrystallize into something else, react with air pollutants or oxygen. A bewildering range of chemical processes can lead to the destruction of geological specimens. Fossils are affected, too: lovely pyritised ammonites turn to dust. Many specimens of scientific or historic importance can be lost in this way.

Museums do their best to halt the decay but are hampered in their efforts by many questions yet unanswered. What levels of indoor air pollutants are safe for geological collections and how good do our air filtration systems need to be? At what point do museum conservators need to deal with a specimen damaged by chemical reactions? How do we even monitor collections of tens of thousands of specimens for damage routinely?

These and many other related questions will be investigated in a new research project at National Museum Cardiff. A recent pilot study (manuscript in preparation) demonstrated the complexity of potentially damaging processes in a typical museum store that are thought of usually as benign. Further expertise in the form of academic and industrial partners is now sought to develop the potential for addressing elementary questions of appropriate storage of geological collections.

The knowledge generated by this project will be of wide-ranging interest to cultural institutions and industrial companies alike. Scientific specimens and commercial collections will be kept safe with the set of guidelines and standards which the project will develop. We will have the proper tools to enable us to care for our geological heritage appropriately - whether kept in museums or as commercial assets.

Find out more about Care of Collections at Amgueddfa Cymru - National Museum Wales here.

Our conservation volunteers are helping to get Christmas underway at St Fagans. The first historic building to get the festive treatment was Cilewent Farmhouse originally from Rhaeadr Powys. The display reflects life as it was in the 18th century with most of the furniture dating to 1750. Preparations for Christmas would involve decorating the home with evergreen foliage gathered from the surrounding countryside, such as laurel, ivy, holly and yew. A tradition that has its origins firmly rooted back in our pagan past and continues to this day with the Christmas tree.

The evergreens stand out among the dormant trees in the museum grounds so it didn't take long to gather up enough to prepare the garlands for Cilewent.  We also created a bracket out of 4 sticks of even length (80cm) and to this attached more evergreen foliage and red ribbons. Red berries were very popular, but these dry out and fall off quickly. A recommended technique to help preserve their colour was to store the berries in salt water after picking, we haven't tried this yet, but we'll probably give it a go next year as a flash of red would definitely enhance the overall effect.

The garlands were much bigger than we anticipated and they soon turned into rather unwieldy evergreen snakes, but between us we managed to walk them across the site and secure them to the beams of Cilewent.

If you would like to try this out at home be careful with the holly, it can scratch, not just yourself but furniture and wallpaper as well, so remember to place a barrier of card or fabric between holly and any vulnerable surfaces.

Well, one house done, 11 more to do and only 20 days to Christmas!

This week is Chemistry Week and our Preventive Conservation team got involved. Two local high schools (St Teilo’s Church in Wales High School and Cardiff High School) were invited to participate in a workshop with live demonstrations and hands-on activities.

We organized the workshop in a collection store and one of our analytical laboratories at National Museum Cardiff. Neither space is laid out for large numbers of people and it’s always a bit of a squash. But once we had squeezed the last of the year 12 and 13 students into each room and closed the doors, there was no escaping the exciting world of analytical chemistry.

The students learned about Wales’s largest and most important mineral collection, the challenges of caring for it, and some of the analytical tools that help us: X-Ray diffraction (XRD), gas detection tubes, infrared spectroscopy (IR) and Nuclear Magnetic Resonance (NMR). The XRD is part of the National Museum's own analytical facilities, operated by Tom Cotterell and Amanda Valentine-Baars in the Mineralogy/Petrology section. The other two technologies are covered by the curriculum and the students enjoyed the opportunity to prepare real samples, analyse them and interpret the results. To them, this made the subject a lot more real than just learning about them from books. It was also important that the analyses were undertaken not simply as a method per se, but in the context of answering genuine research questions at the museum.

What does chemistry have to do with the care of collections? We undertake our own research on objects and specimens in the collections, and we collaborate with researchers at universities. In addition, the act of preserving our common heritage often throws up problems, as objects degrade and conservators need to work out why, and how to stop the degradation.

Often we cannot do this on our own, in which case we work with partners to investigate, for example, the corrosivity potential of indoor pollutants and their effect on mineral specimens in storage at National Museum Cardiff. These partners include Cardiff University’s Schools of Chemistry, Engineering and History, Archaeology and Religion (Conservation Department).

One of these collaborations sparked yesterday’s schools engagement project, run in conjunction with the museum's Conservation and Natural Sciences departments and kindly supported and funded by the Royal Society of Chemistry (South East Wales Section). The Royal Society of Chemistry provided an entire bench full of portable analytical equipment for the day, which the society's Education Coordinator, Liam Thomas, set up in the Mineral Store. Because of the interdisciplinary nature of the project, additional support came from Cardiff University’s School of Earth and Ocean Sciences.

Find out more about care of collections at Amgueddfa Cymru - National Museum Wales here.

This week we managed to combine cleaning floors with a fitness routine and aroma therapy.  Who said housework can't be Fun!

Hannah Glasse, writing in her 18th century books ‘Servant’s Directory ‘ and ‘Housekeeper’s Companion’, advised using green herbs to clean wooden floors.
We couldn't resist having a go and it just happened that the floorboards in our 18th century Kennixton farmhouse required a bit of attention.

Like us today in the conservation team, wetting floors to clean them was considered to be a bad idea in the 18th century. It would introduce damp into the house and excess water could damage furniture and precious soft furnishings and carpets. 
Hannah recommended taking green leaves of Tansy, Lemon balm, Mint and Fennel, all of which we have growing in abundance in the cottage gardens. The herbs are then strewn across the floor and rubbed in with a broom.  The oils are released and nourish the wood, while the moisture activates the dirt, which is then taken up by the leaves.

We left the floor to dry overnight before sweeping up the debris the next day. Hannah then recommends polishing the floor with a dry rubbing brush, which should bring the wood up to a fine brown colour, just like mahogany. 

The herbs would also impart a sweet smell creating a natural air freshener. An added bonus for us is that the herbs Hannah recommended are also natural pest repellents that we normally dry and use throughout the cottages to protect our woollen textiles from moth or carpet beetle attack, so hopefully the lingering aroma will also deter pests from making a home.

It worked! All that Hannah promised came true. Our wooden floors appeared darker and shinier and the smell was amazing, we’ll definitely be doing this again.
 

Nothing lasts forever, not even in your favourite museum. The job of the conservator is to preserve the national collection but decay is all around us. Sometimes it feels like being a surgeon on an intensive care unit. Fortunately we do have a lot of science and technology to help us.

I have recently written about how we refurbished a collection store because corrosive gases being emitted from wooden cupboards caused some metal objects to show early signs of decay. In this blog I want to walk you through the science and analysis behind this project.

Iron rusts, every kid knows that. Leave a nail out in the garden and within weeks, days perhaps, you will notice it develops a lovely orange colour; given enough time, some moisture and oxygen it will eventually become flaky, friable and disintegrate. What happens when iron rusts? Iron atoms react with oxygen and water molecules, leading to oxidation of iron. The result are hydrated iron oxides, a small family of minerals commonly called rust.

Rusting iron has long been a bane of humanity. The Forth Bridge has to be repainted over and over again because it didn’t it would rust and collapse into the Firth below. The same is true of our own Menai Suspension Bridge here in Wales. Wales was the place for the invention of a rust-proofing process for household products made of iron. In the late 17^th Century, Thomas Allgood of Pontypool developed a coating for iron involving the use of an oil varnish and heat. This process was called ‘japanning’, as a European imitation of Asian lacquerwork. Pontypool Museum has lots of information about these old local industries on its website so please visit there if you would like to know more.

National Museum in Cardiff has a collection of Welsh japanned ware which was largely acquired during the early years of the National Museum. Many of these objects do not consist of iron alone: lead, tin, copper and zinc all feature in varying proportions in different parts of some of the objects. Complicated parts, such as handles and bases, were parts made from softer metals or alloys. We can find out what materials an object is made of using a completely non-invasive technology called X-ray Fluorescence (XRF). XRF directs X-rays towards an object and analyses the X-rays that bounce back. As different elements have their own, unique X-ray fluorescence which the instrument can identify and even use to quantify the elemental composition of objects without having to take a physical sample.

The problem for the museum conservator is that many of these metals, too, corrode under certain circumstances. In the case of the objects which were subject to the previous blog the corrosion of parts with a high lead component was accelerated by the high organic acid concentration within the old storage cupboards. A number of analytical tests exist for identifying and quantifying organic acids in air; we used small discs with an absorbent material that were exposed to the air in the store (both inside and outside of the cabinets) and later analysed in the lab. The results of this test showed that the concentration of acetic acid was 623µg/m³ (250ppb) inside the cabinets and 19µg/m³ (8ppb) in the store, and the concentration of formic acid 304µg/m³ (159ppb) inside the cabinets and 10µg/m³ (5ppb) in the store.

We know that both acetic and formic acids are emitted by wood, and both acids can react with various metals to produce, in some cases, some impressive corrosion products. Clearly, the concentrations of both acids were higher inside the storage furniture than in the store itself, giving us a massive clue that the problem was caused by the cabinets and not air pollution entering the store through the air conditioning system. The fresh air supply into the store, on the other hand, kept the concentration of pollutants low in the store itself.

Corrosion and decay comes in many forms, and we also use other technologies to help us identify corrosion products. Of these more in a future blog. In the meantime we are continuing to eliminate the sources of corrosive substances from the museum to help preserve the national collection.

Find out more about care of collections at Amgueddfa Cymru - National Museum Wales here.