Amgueddfa Blog: Conservation

2019 is the 150th anniversary of the Periodic Table of Chemical Elements (see UNESCO https://www.iypt2019.org/). The "International Year of the Periodic Table of Chemical Elements (IYPT2019)" is an opportunity to reflect upon many aspects of the periodic table, including the social and economic impacts of chemical elements.

Sulphur is the fifth most common element (by mass) on Earth and one of the most widely used chemical substances. But sulphur is common beyond Earth: the innermost of the four Galilean moons of the planet Jupiter, Io, has more than 400 active volcanoes which deposit lava so rich in sulphur that its surface is actually yellow.

Alchemy

The sulphate salts of iron, copper and aluminium were referred to as “vitriols”, which occurred in lists of minerals compiled by the Sumerians 4,000 years ago. Sulfuric acid was known as “oil of vitriol”, a term coined by the 8th-century Arabian alchemist Jabir ibn Hayyan. Burning sulphur used to be referred to as “brimstone”, giving rise to the biblical notion that hell apparently smelled of sulphur.

Mineralogy

Sulphur rarely occurs in its pure form but usually as sulphide and sulphate minerals. Elemental sulphur can be found near hot springs, hydrothermal vents and in volcanic regions where it may be mined, but the major industrial source of sulphur is the iron sulphide mineral pyrite. Other important sulphur minerals include cinnabar (mercury sulphide), galena (lead sulphide), sphalerite (zinc sulphide), stibnite (antimony sulphide), gypsum (calcium sulphate), alunite (potassium aluminium sulphate), and barite (barium sulphate). Accordingly, the Mindat (a wonderful database for all things mineral) entry for sulphur is rather extensive: https://www.mindat.org/min-3826.html.

Chemistry

Sulphur is the basic constituent of sulfuric acid, referred as universal chemical, ‘King of Chemicals’ due to the numerous applications as a raw material or processing agent. Sulfuric acid is the most commonly used chemical in the world and used in almost all industries; its multiple industrial uses include the refining of crude oil and as an electrolyte in lead acid batteries. World production of sulfuric acid stands at more than 230 million tonnes per year.

Warfare

Gunpowder, a mixture of sulphur, charcoal and potassium nitrate invented in 9th century China, is the earliest known explosive. Chinese military engineers realised the obvious potential of gunpowder and by 904 CE were hurling lumps of burning gunpowder with catapults during a siege. In chemical warfare, 2,400 years ago, the Spartans used sulphur fumes against enemy soldiers. Sulphur is an important component of mustard gas, used since WWI as an incapacitating agent.

Pharmacy

Sulphur-based compounds have a huge range of therapeutic applications, such as antimicrobial, anti-inflammatory, antiviral, antidiabetic, antimalarial, anticancer and other medicinal agents. Many drugs contain sulphur; early examples include antibacterial sulphonamides, known as “sulfa drugs”. Sulphur is a part of many antibiotics, including the penicillins, cephalosporins and monolactams.

Biology

Sulphur is an essential element for life. Some amino acids (cysteine and methionine; amino acids are the structural components of proteins) and vitamins (biotin and thiamine) are organosulfur compounds. Disulphides (sulphur–sulphur bonds) confer mechanical strength and insolubility of the protein keratin (found in skin, hair, and feathers). Many sulphur compounds have a strong smell: the scent of grapefruit and garlic are due to organosulfur compounds. The gas hydrogen sulphide gives the characteristic odour to rotting eggs.

Farming

Sulphur is one of the essential nutrients for crop growth. Sulphur is important to help with nutrient uptake, chlorophyll production and seed development. Hence, one of the greatest commercial uses of sulfuric acid is for fertilizers. About 60% of pyrite mined for sulphur is used for fertilizer manufacture – you could say that the mineral pyrite literally feeds the world.

Environment

Use of sulphur is not without problems: burning sulphur-containing coal and oil generates sulphur dioxide, which reacts with water in the atmosphere to form sulfuric acid, one of the main causes of acid rain, which acidifies lakes and soil, and causes weathering to buildings and structures. Acid mine drainage, a consequence of pyrite oxidation during mining operations, is a real and large environmental problem, killing much life in many rivers across the world. Recently, the use of a calcareous mudstone rock containing a high proportion of pyrite as backfill for housing estates in the area around Dublin caused damage to many houses when the pyrite oxidised; the case was eventually resolved with the “Pyrite Resolution Act 2013” allocating compensation to house owners.

Conservation of museum specimens

Because iron sulphides are highly reactive minerals, their conservation in museum collections poses significant challenges. Because we care for our collections, which involves constantly improving conservation practice, we are always researching novel ways of protecting vulnerable minerals. Our current project, jointly with University of Oxford, is undertaken by our doctoral research student Kathryn Royce https://www.geog.ox.ac.uk/graduate/research/kroyce.html.

Come and see us!

If all this has wetted your appetite for chemistry and minerals, come and see the sulphur and pyrite specimens we display at National Museum Cardiff https://museum.wales/cardiff/, or learn about mining and related industries at Big Pit National Coal Museum https://museum.wales/bigpit/ and National Slate Museum https://museum.wales/slate/.

Continuing the international year of the periodic table of chemical elements, for August we have selected arsenic.

Preserving the Beasts – The Use of Arsenic in Taxidermy

The taxidermy animals are a much loved and visited part of displays at the Museum. The word ‘taxidermy’ itself comes from taxis ‘arrangement’ and derma ‘skin’, and is the art of mounting or replicating animal specimens in a lifelike way for display or study.

The development of the methods used to create taxidermy date back over three hundred years. Initially these didn’t preserve the prepared specimens very well, and the taxidermy mounts were usually lost to decay and insects.

Various attempts were made to improve preservation methods and these used a wide variety of materials such as herbs, spices and various salts, applied as powders, pastes and solutions. However these methods were not generally successful.

During the 1700s’ some taxidermists started to use more poisonous chemicals such as arsenic minerals or mercuric chloride to help preserve their taxidermy. Due to their toxic nature these treatments helped prevent decay and insect damage, greatly improving the long term preservation of the taxidermy.

The success of these chemicals soon led to the development of the ‘arsenical soap’ treatment to aid preservation of the animal skin. The soap was a mix of camphor, powdered arsenic, salt of tartar, bar soap and powder lime – I wouldn’t use this for washing yourself though! The soap enable the arsenic to be applied in a practical way by rubbing into the underside of a cleaned and prepared skin. This method proved very popular and remained in use up until as recently as the 1970s’.

The use of arsenic as part of the preservation treatment has since stopped. This is mainly because of its toxic nature and the associated risks to human health, but it is also due to better practices in the taxidermy techniques used today.

Inorganic arsenic (As) is a grey-appearing chemical element with the atomic number 33 on the atomic table. It is a metalloid meaning that it has both metallic and non-metallic properties. Its properties have long been used by humankind in a variety of ways such as a medicinal agent, a pigment and as a pesticide. Arsenic and its compounds are especially potent poisons and hence harmful to the environment and considered carcinogenic. Its toxicity to living things is due to the way it disrupts the function of enzymes involved in the energy cycle of living cells.

Does this then mean that our older taxidermy specimens containing arsenic are harmful in some way? Potentially yes if a specimen is damaged and the underside of the skin is exposed, but an intact specimen poses little risk provided sensible precautions are taken such as appropriate protective equipment when moving or conserving an affected specimens.

Besides, today most of the specimens we have on open display are preserved without the use of toxic chemicals, but such specimens are at greater risk of damage by insects. We thus monitor our collections to look out for the signs of insect infestation, and treat with safe and sustainable methods such as freezing if they occur.

But a good reason not to touch the specimens…..

Amgueddfa Cymru helped direct me to a career in heritage by drawing my attention to the possibility of a career in museums at a “career speed dating” event. I would go on to volunteer with National Museum Cardiff, whilst studying.

Volunteering as part of the museum’s preventive conservation team, we carried out a wide range of tasks from repackaging lichen, to carefully carrying jade, cleaning paintings currently on display all the while talking to the public about the importance of preventive conservation and promoting part of the Museum traditionally shielded from view. It could be just a few people or what seemed like hundreds of school children, every day brought a different experience.

Volunteering brought the reality of the sector and a chance to learn new skills and experiences which were invaluable to my understanding of what museums are and who they are for; fulfilling my personal reasons for volunteering.

The volunteer programme was flexible, reflecting my own needs not just its own. The programme allowed me to develop as I wanted and when it came time to end my time volunteering with Amgueddfa Cymru it was natural. I had succeeded in what I wanted to achieve, and I was supported to continue my development beyond the museum, not expected to stay when it was no longer practical.

I will always remember having the opportunity to be part of the preventive conservation team, I am sure the team will not forget my Elmer the Elephant style shirt, immortalised in many presentation slides and pull up banners (see photos). I now work for the Cynon Valley Museum as a Museum Co-ordinator and advocate for museums through EMP Wales (Emerging Museum Professionals) and FOH. 

Follow me on twitter: @TregaskesW @FoHMuseums @EMPCymru @cynonvalleymus

What do you do if you have minerals in your collection that have a tendency to react chemically? For our research student Kathryn Royce this means: growing minerals from a super saturated solution, then sticking the crystals in a climate chamber for a few weeks and forcing them to dehydrate.

Yes, you read right, some minerals can dehydrate. There is a good number of mineral species which are poly-hydrated, meaning, minerals that contain water molecules as part of their crystal structure. Many of these mineral species can, under certain conditions, lose some of these water molecules. This process actually turns the mineral into a different mineral – just one with a lower hydration status.

For example, the mineral melanterite (FeSO4 · 7H2O), which has 7 water molecules, may lose some water molecules if kept at a relative humidity below 57%. The resultant products include either the mineral siderotil (same chemical formula but only 5 water molecules) or rozenite (4 water molecules). In the context of wanting to preserve melanterite in a museum collection, the dehydration products siderotil and rozenite, whilst minerals in their own right, would be classed as deterioration products and, hence, their appearance be undesirable.

To understand this process, and define how we would characterise the concept of ‘damage’ to mineral specimens, Kathryn is now analysing the deterioration products using a combination of different analytical techniques, including X-ray diffraction, electron microscopy, Raman spectroscopy and computerised tomography scanning. The results will help us develop a methodology for long-term monitoring of geological collections in museums and improve the care of such collections in museums.

This research is being undertaken at National Museum Cardiff in collaboration with the School of Geography and Environment at University of Oxford and the EPSRC Centre for Doctoral Training in Science and Engineering in Arts, Heritage and Archaeology (SEAHA), and kindly supported by OR3D, BSRIA, the Barbara Whatmore Charitable Trust, the National Conservation Service, and the Pilgrim Trust.

Find out more about Care of Collections at Amgueddfa Cymru - National Museum Wales here and follow us on Twitter

One of the best reasons for housing heritage collections inside buildings is that the building keeps the weather out. Paintings, fossils, books and skeletons are best kept dry, and walls and roofs protect our collections (as well as staff and visitors) from the elements.

In addition, many of the objects in our collections also need specific temperature and humidity ranges to prevent them from suffering damage. Too high a humidity can cause swelling of wood, for example, initiating cracks in objects, or, if humidity gets even higher, mould growth. Therefore, National Museum Cardiff has a complicated air conditioning system. This system is more than 40 years old and has been maintenance-intensive and inefficient for some time.

We are happy to report that, after several years of planning, we have just completed the installation of new chillers and humidifiers at National Museum Cardiff. The purpose of chillers in the museum is to provide cold water – for lowering the temperature of galleries and stores in the summer, and for dehumidifying stores and galleries if there is too much moisture in the air. Humidifiers achieve the opposite effect: they increase humidity in stores and galleries if it is too low. Low humidity is usually a problem during the winter months – you may have experienced your skin drying out at home when you have the heating on in winter. To prevent our collections drying out we cannot apply skin cream; instead, we maintain a minimum level of humidity in stores and galleries.

The chillers and humidifiers have been commissioned now, and are working well. They have already proved that the control of our indoor environments is better than it was before. A very positive side effect of the new technologies is that they are much more efficient than the old equipment. In fact, they are so efficient that we are anticipating to shave almost 50% off our annual electricity bill for National Museum Cardiff, saving the planet more than 500 tonnes of carbon dioxide every year. That is the equivalent of taking 100 cars off the road, or the average energy a family home uses in 38 years.

By investing in such new technologies, Amgueddfa Cymru – National Museum Wales continues to ensure the safe storage and display of the nation’s heritage collections, whilst at the same time making a massive contribution towards the National Assembly’s commitment to reduce carbon emissions by 80% by 2050 (Environment Wales Act 2016).

Find out more about Care of Collections at Amgueddfa Cymru - National Museum Wales here and follow us on Twitter. Follow the progress of the maintenance works during the coming months in 2019 on Twitter using the hashtag #museumcare.