: Preventive Conservation

Dropping a rusty nail into a glass of Coca Cola will clean it in a matter of hours. We have all heard that one. Other drinks manufacturers are available, and alternative liquids will do the same job: lemon juice, vinegar, even salad dressings.

What causes the nail to go rusty in the first place is corrosion. Rust is the product of the corrosion of iron, and I bet my favourite chemistry book that you will have seen rust somewhere. Many other metals can corrode, too: aluminium, zinc, lead, copper etc. Corrosion is electrochemical oxidation; it usually needs water and oxygen to corrode a metal. If you drop a clean nail into a salt solution (electrolyte) it will start rusting within hours – the iron loses electrons and gains oxygen. The acidic liquids in the first paragraph appear to have the opposite effect but, in fact, dissolve the rust rather than convert it back to the base metal.

This blog is turning into a mixture of a cooking recipe and a heavy science article. What on Earth does all this have to do with museum collections? After all, we don’t allow food consumption in our galleries and stores so where does the vinegar come from?

Well, believe it or not we do have vinegar in the air in the museum. You do, too, at home. Along with formic acid, acetic acid (the thing that gives vinegar its zingy taste) can be air borne in indoor environments. Both acids are considered indoor pollutants. Hardly detectable outside, in certain conditions they can accumulate inside buildings – and then cause corrosion. Indoor air pollution has recently been in the press, but we are talking here of risks to museum objects, not health risks to people.

Where do these substances come from? Wood readily off gasses acetic and formic acids. Book cases, furniture, floor boards, the wooden boards your walls are made of – they all emit these substances. Normally, this is not a problem; we all ventilate our houses, and normally we don’t keep objects at home long enough for corrosion to be a problem. Or is it? My mother still polishes her silver regularly and keeps it safe – in a wooden cupboard. Make of that what you want. Perhaps she enjoys polishing.

Your favourite museum has a lot of metal objects in its stores. And we are, of course, in the business of keeping objects safe not just for short periods of time, but for centuries. Over long periods of time we do notice corrosion on metal objects even if they merely sit on a shelf. We could go round cleaning these, like my Mum does, and give them a polish from time to time. Time consuming, I hear you cry. You lose a teeny tiny part of the surface each time you polish it, I hear you scream. And wouldn’t it be better to prevent corrosion in the first place, I hear you shout.

Right you are, I respond. After all, this is Preventive Conservation. We can measure the concentrations of air borne acids with good accuracy. We also know the sources of these acids. So when we detect signs of corrosion all we need to do is some simple investigating and – hey presto – come up with a mitigation plan. In some cases this might mean replacing old, wooden storage furniture. In others, we might have to introduce ventilation to a store to prevent pollutants from accumulating to harmful levels. Either way, the collections will benefit.

At National Museum Cardiff we have done both, and with good success. We have recently refurbished two stores with the sole aim of reducing indoor pollution. This was not cheap, but it is more cost effective than constantly polishing the silver ware - over and over and over again. It is because of these constant collection care improvements that we can say, hand on heart, your heritage is safe in the museum. And why we only eat fish and chips without vinegar in the museum. Only joking – food is still banned. Don’t let me catch you with any chips in the galleries!

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

National Museum Cardiff has an enormous number of artefacts displayed for people to see, with an even greater collection held in storage. Stores are customized to prevent any damage to objects. Storage furniture depends on the size and type of objects, and ranges from pallets to open racking and cupboards with doors. The Museum always tries to improve storage facilities, and when a store is refurbished all objects have to be moved.

This is where we encounter problems: how do you move several hundred historic objects, including fragile china, glass and heavy jade, safely without damaging them? Though the greatest of care will be taken, moving objects always carries a risk of damage. An old repair may fail, or a piece may come off a 100-year-old Chinese painted plate after a slight touch. The Museum has many procedures to avoid such damage. Handling guidelines include holding the artefact with both hands, and not picking up vases by the handle, as old repairs often cannot hold the strain. Notes will be taken of any parts that may be lose or detached, so that they can be fixed.

Should ever any damage occur the most important thing to remember is not to panic. The conservation professional would record, with forensic diligence, the smallest detail to enable the object’s repair. Museums, of course, have procedures even for dealing with accidents. There are some famous examples of museum objects breaking, including a visitor falling into three 17^th-century Chinese vases. Things may break in your kitchen at home or in a museum. The difference between the two is the way any potential breakage is treated.

By the way, when one of the art stores was refurbished recently at National Museum Cardiff and hundreds of delicate objects had to be moved, not a single one was damaged, thanks to careful handling procedures.

Elizabete Kozlovska

Elizabete is a student at Cardiff University's School of History, Archaeology and Religion and volunteers one day a week with the Preventive Conservation team at National Museum Cardiff.

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

Y Garreg Fawr from Waunfawr in Gwynedd was built in 1544, and is a fine example of a Snowdonian house. At the time, these homes were some of Wales’s finest and represented the beginnings of the modern home we know today. Prior to this date, the wealthy Welsh lived in timber-framed hall-houses. These were often single-story buildings comprised of three bays in a linear arrangement: a ‘service’ bay of a dairy and larder, a ‘solar’ – which was the bedroom - and in-between was a large hall with a central hearth, and was open to the rafters. Although Y Garreg Fawr has a hall, service end and solar, it represents a radical departure from the previous medieval plan by introducing some key developments. Choosing to build in stone allowed the creation of a pair of effective chimneys - one on each gable. These in turn allowed the creation of a first-floor featuring heated, smoke-free rooms.

Y Garreg Fawr (The Great Rock) was named after the large exposed rock outcrop behind the house. Two other Snowdonian type houses share a similar important-sounding name. Both are called ‘The Great House’ – Tŷ Mawr Wybrnant and Tŷ Mawr Nantlle – names that highlight their physical grandeur as well as the high social standing of their owners. Y Garreg Fawr was is a rare survival of national significance, but by 1976 (432 years later) it was barely recognisable and in a serious state of disrepair. At the time, the only way to ensure its survival was to move it stone by stone, some 165 miles, to St. Fagans National History Museum where it could be rebuilt. 40 years later it is undergoing a programme of restoration. 

A recent inspection of Y Garreg Fawr revealed that the inner surface of its walls had been rendered with cement. This is an out-dated practice that is not in keeping with current methodologies. Work is now underway to remove the cement and re-place it with lime mortar, which should allow the building to breathe better, and allow it to stand for several more centuries. Y Garreg Fawr is now closed for a number of months to allow this work to continue.

Don't worry no violence was involved. It was the turn of Llainfadyn this week, our quarrymen’s cottage from Gwynedd, to receive a clean and make over from our Historic Interior and Conservation Volunteer team. It was a big task so thanks to everyone involved. This included stripping the beds and giving everything including the feather mattresses a good airing and beating to remove a winter's worth of dust and dirt. As long as the textiles are strong enough this is still a very effective method of removing grime without the aid of modern appliances.

We also held a competition between a modern broom and a traditional one made from hazel twigs (that all important witches’ accessory at Halloween). To help protect the collections on display it's important we try and reduce the amount of dust and dirt being brought into the houses by our thousands of visitors each year. Our first line of defence to achieve this is the cobbles outside, these help dislodge the grit and dirt from peoples' shoes before they even enter the building, but for these to work the cobbles need to be clean and not clogged up with dirt. So one of our first important tasks was to clean the stones outside.

So which broom won? The traditional of course, with its long twiggy brush it was the best at dislodging the dirt from between the cobbles. This job would certainly have been an everyday task for most households in the past.

Our second line of defence to keep the dust down is the rag rug, often found in cottages of this period. These were made from scraps of material or worn out clothes and blankets, so as well as providing much needed comfort and colour they were great at trapping dirt. They could then be picked up, taken outside and beaten with a carpet beater to remove the grime. We are currently making one for Llainfadyn, unfortunately the odd hail storm meant that Jane and Emma had to find seats by the open fire to carry on their work.

Sorry about the awful pun in the title. But, yes, it's that time of year, the sun is out, spring's officially here and it's getting warmer. Fantastic you may say, but for our Conservators and Volunteers a new battle is about to begin! As well as our lovely lambs and piglets, less desirable creatures are stirring. These are the insect pests, such as moths, carpet beetles and woodworm, that if left unchecked would quite happily eat our museum and its collections!

This week the volunteer conservation team were introduced to the enemy. In the natural world these insects perform an essential task, but in the confines of our historic houses, or anyone's home in fact, they can cause untold damage especially to items made from wool, fur, feathers, leather, paper and wood.

We have decided to go for a two-pronged attack. The first is to re-introduce traditional deterrent methods. Last year we worked with the gardening team collecting and drying a range of aromatic plants such as Tansy, Wormwood, Rue, Rosemary and Lavender traditionally used to deter insects. From the selection grown in our gardens we have created the extremely potent St Fagans blend.

Now we are devising ways to deploy our deterrent in sufficient quantities that might have an effect. For this we found tights ideal for the task! Yes, that's correct, tights. These are especially useful for items of clothes hung up on display, they enable us to place the aromatic plants in the more inaccessible areas of a garment, such as down sleeves!

The second method of attack is of course good old fashioned housekeeping. Spring is the time to open up the house after a long winter and give everything a good clean, or in our case a good beating.