The Museum at Work

Specimen showing attack by biscuit beetle.

Testing for mercury vapour levels inside the herbarium cupboards.

An example of pesticide discolouring. Research showed that this specimen had been treated with arsenic, mercury and barium - substances harmful to both specimen and health.

Amgueddfa Cymru house over quarter of a million dried plant specimens from all over the world, some dating back to the 18th century. Toxic pesticides applied to these specimens over the years can cause damage to the specimens and be a risk to those working with them.

Pesticides are applied to the specimens to overcome pests such as booklice, biscuit beetle and silver fish. Natural history specimens have always been vulnerable to attack from pests, which can be devastating to a botanical collection, as important details, or even whole specimens, can be lost.

Some types of pesticides used in the past are now known to be harmful and toxic. Handling the collections could present a health risk, especially as the quantity and nature of chemicals used in the pesticide were unknown.

Small samples of the Museum's herbarium sheets were analysed to detect the chemicals present within one sample. For example, if mercury and arsenic had been applied to a herbarium sheet then this would identify the two metals in one test.

It was discovered that the most frequently used chemicals were carbon disulphide, mercuric chloride, methyl bromide, naphthalene, paradi-chlorobenzene and pyrethroids.

Mercury

High levels of mercury were found within the paper samples and immediate precautions were taken for handling specimens. Mercury can be absorbed through inhalation, absorption and ingestion and its effects can result in reduced fertility, possible genetic mutations, shakes, reduced vision, serious personality changes and even brain damage.

The herbarium air quality was monitored for mercury vapour and each site tested had readings well below the recommended health and safety standard. Individuals were monitored by attaching the monitoring instruments directly to their clothing.

Moth Balls and Arsenic

Although it is difficult to measure arsenic accurately, it was discovered on most of the specimens tested. The presence of naphthalene was detected on all samples, which was as expected. Moth balls, made from naphthalene, were only removed from herbarium cupboards in the 1980s.

The project successfully identified the hazardous chemicals and metals present within the pesticide residues and through continued monitoring of air quality and staff, work can now continue within the herbarium without risk.

Following the tests, a database was generated detailing specimens, pesticide, contaminants and risks to both health and the specimens, which has since been used to help identify hazards in herbariums from other botanical institutions.

Leopold Blaschka, about 1895. Image courtesy of The Botanical Museum, Harvard University, Cambridge, MA.

Rudolf Blaschka, about 1895. Image courtesy of The Botanical Museum, Harvard University, Cambridge, MA.

A source picture of the Paper Nautilus (Argonata argo) model.

A broken Paper Nautilus model.

The Paper Nautilus model after conservation.

Amgueddfa Cymru holds around 200 beautifully detailed glass models of sea creatures created by Leopold and Rudolf Blaschka. Made in the latter half of the 19th century, these intricate and extremely fragile items have been subject to years of open display and poor storage conditions, causing them to become damaged and dirty.

Irreplaceable works of art

These beautiful glass representations of marine animals were originally developed as educational models. Now they are now considered to be works of art, with a value that makes them irreplaceable.

Conserving the Blaschka models is fraught with difficulties. Given their age and complexity, great care has to be taken before attempting to clean or repair the models. The accumulation of decades of dirt, and damage from past repairs must be rectified without damaging or altering the original model.

The first stage of any conservation project is to understand what the object represents, and then to understand how it is made. The Blaschka models are an intricate blend of glass, paint and textured coatings that have been put together to show the textures and colours of the animal in life.

Shifting decades of dirt

Firstly, a suitable way of cleaning the models had to be found, then methods had to be developed for removing previous repairs. Finally, where required, the models needed to be repaired.

The models proved to be very difficult to clean. Surface paint had been applied to many of the specimens to add texture and colour. These had attracted surface dirt over the years, which was very hard to remove.

A range of solvents and cleaning solutions were carefully tested. Whilst water (with a non-ionic detergent) proved effective for removing the dirt, the surface paint was soluble and was in danger of being washed away. Eventually white spirit was found to shift the dirt without damaging the original surface paints.

Removing past repairs

Many of the specimens, especially the cephalopods, had become repeatedly broken and repaired over time. Many of these repairs were now discoloured or failing. Some parts, for example tentacles, had been re-attached in the wrong place.

The older repairs tended to use animal glue that could easily be softened in water, but this required care where the surface paint was present as this was water soluble. Other glues were dissolved by acetone. Once the old glues had been removed, the models then had to be reassembled.

Re-repairing correctly

The glass used to manufacture most of the models was very thin and brittle. Some of the collection had been broken into numerous pieces, and, in the past, detached pieces were fitted back in the wrong place.

Firstly, any new repairs made to the models needed to be reversible in the future. Epoxy resin based adhesives were quickly ruled out due to their strength, lack of reversibility and long-term stability problems. The consolidant, Paraloid B-72TM, was chosen because it is a stable material that remains reversible and can be removed if required. It is also forms a weak repair that will fail before the glass, reducing the chances of damaging the models further. This material is also slightly visible in certain lights, allowing future curators of the collection to identify previous conservation work.

The conservation work was developed to improve the visual appearance and integrity of the models, without further altering the original structure. The Blaschkas' glass models are an important collection, which is still used today. The work carried out on the collection will help ensure its continued survival for future generations to enjoy.

During the late 19th century, Leopola Blaschka (1822-1895) and his son Rudolf (1857-1929) produced beautifully detailed glass models of bizarre sea creatures for natural history museums and aquaria all over the world.

Their work has been hailed as: “an artistic marvel in the field of science and a scientific marvel in the field of art.”

Today, the Blaschkas seem remarkably contemporary: working as they did on the cusp of design, craft, art and industry.

Click the thumbnails below to view larger images from a selection of these remarkable glass models held at Amgueddfa Cymru.

Roman Trawsfynydd

The first 'page' of a Roman will found near Trawsfynydd in the 19th century. The tablet was already broken in two.

Britain's only surviving Roman will was found in the 19th century near Trawsfynydd, Merionethshire. Two letters written at the time shed light on its history.

The first letter describes a 'wooden book', consisting of 10 or 12 leaves, as being found by farm servants cutting peat 5km to the south-east of the Roman fort at Tomen-y-Mur. The letter reads:

"I saw the book a few days after it was first found – only 2 or 3 of the leaves then contained the inscription perfect – On the rest it had been partly obliterated by the carelessness of the farm servants. The work is, probably, a relic of the Ancient Druids, who may have employed a modification of the Roman alphabet to write their own language."

The author of the letter was mistaken in linking the text to the Druids, but did well to identify it as Roman, since at this time Roman 'cursive' (joined characters) writing was unknown.

TV show prompts artefact to be identified

Pottery inkwell, an iron stylus for writing on waxed tablets, a seal box and a lead property marker.

The second letter records the delivery, probably in the mid 19th century, of one leaf to George Carr Pearson in London. Pearson studied the tablet, but never returned it. Eventually, the tablet was found again when clearing a house in West Kensington. In 1991 it came into the possession of Mr Stafford Ellerman, who in 2003 saw a television programme about the writing tablets discovered at the Roman fort of Vindolanda on Hadrian's Wall. He realised he too owned a Roman writing tablet and took it to the British Museum for identification. He generously donated it to Amgueddfa Cymru.

The will

Detail of the tablet revealing the Roman writing preserved on its surface.

The tablet is a thin rectangular slab of wood from a silver fir tree, which was not native to Britain. The wax coating on one side is now degraded. Originally this would have been a smooth dark coating made of beeswax and a colouring agent, probably soot, in which the scribe wrote with his 'stylus' (a pointed metal writing tool) to expose the pale wood underneath. Some 300 stylus tablets have now been found on sites in Britain.

With careful photography and meticulous study of the original, it is possible to discern a ghost of writing in many places. The writing is in 'lower-case' Roman cursive script. The tablet forms the first page of a Roman will, written in Latin.

Its author names an heir to his estate, possibly his wife or daughter, and charges them with responsibility for accepting it within 100 days of becoming aware of their inheritance. The identity of the author and the extent of his estate were presumably detailed on the other tablets, now lost.

Considering that Roman wills were regularly written on waxed tablets, with good reason to preserve them and millions of Roman citizens to write them, it is surprising that the actual tablets should be so rare; four are known from Egypt and now this example from Wales.

The text translates as:

"[The name and status of the testator] ... before I die, I order that [name] be my sole heir...

Let all others for me be disinherited [...] on no other terms than that as much as I shall give, have given, shall have ordered to be given [...] and you [enter upon, accept my estate [... within] the next hundred [days] after my death in which you know or can know that you are my legitimate heir, in the presence of witnesses [...] let the heirs be those who know that they are [...] of this property.

But if you do not thus accept my estate, if you refuse to enter upon it, be thou disinherited [...], whom I have instituted as my sole heir."

Background reading

‘A Roman Will from North Wales’ by R. S. O. Tomlin. In Archaeologia Cambrensis, 150 (2004) pp. 143–56

Life and Letters on the Roman Frontier by A. K. Bowman. Published by British Museum Press (1994).

The leopard cup. 11.5cm (4.5 inches) tall.

Detail of the leopard handle, showing its finely worked features and silver spots.

Leopard cup being placed in the Scanning Electron Microscope.

X-rays of the cup.

Microphoto of the leopard's face.

Discovered in 2003, this exquisite Roman vessel has been the subject of detailed study at Amgueddfa Cymru - National Museum Wales.

The bronze cup is one of the finest Roman vessels to have been found in Wales. It was discovered by Mr Gary Mapps near Abergavenny (Monmouthshire). It was reported to the Portable Antiquities Scheme, enabling the finds spot to be investigated.

Excavation of the site revealed that the cup had been placed upside down in a small pit containing a cremation. This cremation was part of a cemetery beside a Roman Road some distance from the mid 1st to early 2nd century fort at Abergavenny (Roman Gobannium). There is also a growing amount of evidence for a civilian settlement dating from the 2nd to 4th centuries in the neighbourhood of this cemetery.

The cup displays craftsmanship of a high standard and it was almost certainly manufactured in Italy during the 1st century AD. Very similar cups have been found at the doomed city of Pompeii, which was destroyed after the eruption of Vesuvius in AD79.

X-rays of the cup revealed that it was first cast in a mould using leaded bronze. Lead was added to help the molten bronze (principally copper and tin) flow more easily and improve the quality of the casting. Once this casting had been made the vessel was turned on a lathe with the use of a sharp cutting tool to produce its final shape.

The cup's decorative handle depicts a leopard which, in Roman mythology, appears as the draught-beast and companion of Bacchus, the god of wine. His worship involved feasting, drinking, music and dancing. Leopards, captured in both Africa and Asia, were also popular with the Romans for display and fighting in the amphitheatre arena.

The leopard handle was made separately using 'lost wax' casting. The first process was to make a wax model of the leopard. A clay mould was formed around the model and then heated to run off the wax. Leaded bronze was poured in to fill the space left by the wax and, after cooling, the mould was broken to remove the bronze handle.

Further work was undertaken on the finished casting: for example the tail and canine teeth, originally cast thicker, were cut away to form finer features. The spots were also chiselled out from the body after casting and inlaid with silver. The leopard was then attached to the cup using solder. The leopard's eyes, measuring about a millimetre in diameter, were also inlaid. Analysis of the remaining traces of inlay indicate that the eyes may have been of amber.

It is unknown whether the cup belonged to a member of the Roman army, or a native Briton from the nearby civilian settlement. Whichever is the case, this 1st century cup was a costly import and probably belonged to someone of status, who cherished it sufficiently to want it buried with them on their death.

Background Reading

Things Fall Apart: museum conservation in practice. National Museum Wales Books, 2006