Rydym yn parhau i nodi blwyddyn ryngwladol tabl cyfnodol yr elfennau cemegol ac, ar gyfer mis Ebrill, rydym wedi dewis calsiwm. Mae’r rhan fwyaf o bobl yn gwybod am galsiwm fel yr elfen sylfaenol er mwyn ffurfio esgyrn neu mewn calchfaen ond mae iddo lu o ddibenion eraill ac mae i'w gael ar wely'r môr ac mewn bywyd morol ddoe a heddiw.

Elfen fetelig o liw golau yw calsiwm (Ca) ac 20 yw ei rhif atomig. Mae’n hanfodol ar gyfer bywyd heddiw ac mae’n aml yn chwarae rhan bwysig yn cynnal planhigion ac anifeiliaid. Dim ond pedair elfen arall sy'n fwy cyffredin na chalsiwm yng nghramen y ddaear ac mae’n rhan o lawer o greigiau a mwynau fel calchfaen, aragonit, gypswm, dolomit, marmor a sialc.

Aragonit a calsit yw’r ddwy ffurf grisialog fwyaf cyffredin ar galsiwm carbonad ac fe gyfrannodd y ddwy at ffurfio’r ddwy filiwn o gregyn yn ein casgliad o folysgiaid. Craidd y casgliad hwn yw casgliad Melvill-Tomlin a gyfrannwyd i’r amgueddfa yn y 1950au. Dyma gasgliad rhyngwladol sy’n cynnwys llawer o sbesimenau prin, prydferth sy’n bwysig o safbwynt gwyddonol ac a ddefnyddir gan wyddonwyr o bedwar ban byd ar gyfer eu hymchwil. Caiff perlau, sydd hefyd wedi’u gwneud o aragonit a calsit, eu cynhyrchu gan gregyn deufalf fel wystrys, cregyn gleision dŵr croyw a hyd yn oed gregyn bylchog mawr. Ym myd natur, caiff perlau eu ffurfio wrth i’r molysgiaid ymateb i barasit ymwthiol neu ronyn o raean. Mae’r fantell o gwmpas corff meddal yr anifail yn gollwng calsiwm carbonad a conchiolin sy’n amgylchynu’r peth estron ac yn dynwared ei siâp ac felly nid yw pob un yn hollol grwn. Yn y diwydiant perlau, caiff pelenni bach iawn o gragen eu 'plannu’ yn yr wystrysen neu’r gragen las er mwyn sicrhau bod y berl a ffurfir yn hollol grwn.

Cyrff meddal sydd gan folysgiaid ac maent yn creu cregyn i fod yn darianau amddiffynnol iddynt. Mae hyn yn wir am anifeiliaid di-asgwrn-cefn eraill hefyd, yn enwedig yn y môr. Mae riffiau cwrel a thiwbiau rhai mwydod gwrychog (Serpulidae, Spirorbinae) yn dibynnu ar natur atgyfnerthol calsiwm carbonad i gynnal a gwarchod eu cyrff meddal. Mae gan gramenogion fel crancod a chimychiaid sgerbwd allanol caled sy’n cael ei atgyfnerthu â chalsiwm carbonad a chalsiwm ffosffad. O gastrolithau y daw’r calsiwm y mae ar gimychiaid, cimychiaid coch, cimychiaid afon a rhai crancod tir ei angen ar ôl bwrw’u cragen. (Weithiau, gelwir gastrolithau’n gerrig stumog neu'n llygaid crancod). Maent i’w cael ar y naill ochr a’r llall i’r stumog ac maent yn darparu calsiwm ar gyfer rhannau hanfodol o’r cwtigl fel darnau’r geg a’r coesau. Yng nghasgliad yr Amgueddfa, mae bron 750,000 o anifeiliad morol di-asgwrn-cefn, yn cynnwys cramenogion, cwrelau a mwydod gwrychog.

O fwynau calsiwm y gwnaed llawer o’r 700,000 o ffosilau sydd yng nghasgliadau’r Amgueddfa hefyd. Defnyddir dau brif fath o galsiwm carbonad i wneud cregyn a sgerbydau allanol anifeiliaid di-asgwrn-cefn, ac maent yn fwy tebygol o gael eu hanfarwoli fel ffosilau os defnyddir un ohonynt yn hytrach na’r llall. Mae aragonit, sydd yng nghregyn molysgiaid fel amonitau, gastropodau a chregyn deuglawr, yn ansefydlog ac nid yw’n para am filiynau o flynyddoedd gan amlaf. Wrth ffosileiddio, mae cregyn aragonit naill ai’n ymdoddi’n llwyr, neu mae’r aragonit yn ailgrisialu i ffurfio calsit. Defnyddiwyd calsit i wneud cregyn a sgerbydau grwpiau o gwrelau sydd wedi peidio â bod erbyn hyn, braciopodau cymalog, bryosoaid, ecinodermiaid a’r rhan fwyaf o drilobitau. Mae’n llawer mwy sefydlog nag aragonit ac felly mae darnau caled gwreiddiol o’r creaduriaid yn ymddangos fel ffosilau, filiynau o flynyddoedd ar ôl iddynt suddo i wely’r môr. Yn aml, gwelir grisialau mawr o galsit yn llenwi mannau gwag mewn ffosilau, fel y siambrau y tu mewn i gregyn amonitau. Mae fertebratau’n defnyddio mwyn calsiwm gwahanol i wneud esgyrn a dannedd: apatit (calsiwm ffosffad), a all bara am filiynau o flynyddoedd i wneud ffosilau eiconig fel sgerbydau deinosoriaid ac ysgithrau mamothiaid.

Yng nghasgliadau’r Amgueddfa o greigiau, mae llawer o galchfeini, creigiau a ffurfiwyd ar waelod y môr amser maith yn ôl o ddarnau o gregyn a deunydd arall sy’n cynnwys llawer o galsiwm carbonad. Ers miloedd o flynyddoedd, bu pobl yn defnyddio calchfeini i adeiladu: cerrig cerfiedig yn nhemlau eiconig y Groegiaid a’r Rhufeiniaid; darnau mâl i fod yn falast o dan reilffyrdd a ffyrdd; neu wedi’u llosgi i greu calch i wneud sment. Defnyddiwyd calchfaen enwog o Dorset o’r enw Carreg Portland i adeiladu Amgueddfa Genedlaethol Caerdydd ac adeiladau eiconig eraill yng Nghanolfan Ddinesig Caerdydd. Ar lawr yr Amgueddfa gwelir teils marmor, sef calchfaen a drawsnewidiwyd o dan wres a gwasgedd mawr. Bu cerflunwyr yn hoff iawn o farmor ers dyddiau’r hen Roegiaid a’r Rhufeiniaid. Yng nghasgliadau celf yr Amgueddfa gwelir gweithiau marmor gan Auguste Rodin, John Gibson, Syr Francis Chantrey, Syr William Goscombe John a llawer o rai eraill. Yn ogystal, mae yno enghreifftiau pwysig o waith gan gerflunwyr o’r ugeinfed ganrif, fel Jacob Epstein, Eric Gill a Henri Gaudier-Breszka. Roedd yn well ganddyn nhw gerfio calchfaen feddalach a llai dwys, Carreg Portland a thywodfaen.

Locust swarms have for centuries destroyed crops and threatened food supplies across large parts of Africa, the Middle East, and Asia. This threat continues today - a recent plague in Madagascar destroyed 2.3 million hectares of crops. Controlling it took three years and cost $37 million.

Desert Locust (Schistocerca gregaria) swarms can move hundreds of miles within a vast ‘invasion area’ that can span dozens of countries, and even continents. To better understand and control such plagues of locusts the British founded the Anti-Locust Research Centre (ALRC) in the 1920s.

The ALRC took the lead in monitoring, studying, forecasting and controlling locust swarms. To do this they had to work with different experts including entomologists (insect specialists), cartographers (map makers), toxicologists (experts on poison), explorers, photographers, the military and local people.

For decades the ALRC gathered information on locusts worldwide. This now forms an incredible archive of thousands of documents, maps and photographs held at the Natural History Museum in London, and a collection of over 70,000 locust specimens that are now part of the collections here at Amgueddfa Cymru.

Our new display ‘Locust War’ reunites the archive and specimens to rediscover the remarkable work of the ALRC and the challenges it faced to understand and control the desert locust.

The exhibition is the work of a collaborative research project led by academics from the University of Warwick, University of Portsmouth and Glasgow School of Art, and supported by the Arts and Humanities Research Council.

‘Locust War’ is part of the displays in our InSight Gallery, and runs until the 16^th September 2019.

It’s true to say that volunteers play a key role in the work of the National Museum of Wales. However, the role of a museum volunteer has changed a fair bit in recent years, so allow me to bring you all up to speed.

My name is Ben Halford and I’ve been an Explore Volunteer at the National Museum of Wales for nearly a year. The role of Explore Volunteer is still rather new. It was introduced into the museum last year with the aim of trialling a new style of volunteering. It merges several types of volunteer into one. It’s our job to engage with the visiting public in our galleries and enrich their museum experience. Because the role is still becoming more established, not many people know what Explore volunteers get up to around the museum, which is where the Explore Blog comes in.

Here we’ll be bringing you stories from volunteers across the museum, which will give you a taste of what being an Explore Volunteer entails. We’ll be including features about our favourite exhibits, our most frequently asked questions from visitors and indeed our strangest questions from visitors (the one about the Siberian dinosaur springs to mind!).

We have many Explore Volunteers who operate in the museum on a regular basis, and they all have great stories to tell. With this blog we now have a way to share these stories and to give you all an insight into what we do as part of this fantastic institution.

We want to hear from any and all volunteers about their experiences, so if you’re interested in writing for the blog please let us know! In the meantime watch this space for brilliant content coming soon!

Students from Cardiff School of Art and Design recently had an exciting opportunity. Not only did they get to spend lots of time at National Museum Cardiff, but a lucky few also got to display their work in our Main Hall!

Moving the Museum was a five-week project which brought together students from across the entire breadth of courses that CSAD offer—including animation, illustration, textiles and ceramics.

After an introduction to the museum and tours of the galleries, the students were tasked with creating original work in response to the wealth of inspiration at National Museum Cardiff. Each student brought their own skills and experience to the project, and it was very interesting to see the variety of ways the students approached the brief.

Including both fine and applied art, the responses encompassed everything from paintings and sculptures to ceramics and textiles. There were even lighting products, metalwork and reinterpretations of Marcel Duchamp’s Box in a Valise, a mini museum full of tiny treasures. We didn't get pictures of everything, but you can see some examples below.

As well as the physical works, there were also several screen-based pieces. These ranged from stop motion animation, explorations of our vertebrate collection and even a trailer for a computer game set in the museum.

The finished projects were presented during a grand finale in our Clore Discovery Centre. To see the finished works and to hear the students discuss their experiences with enthusiasm was a real pleasure. The day felt like a celebration of both the museum’s collections and the students’ creativity and skill.

After the final presentation day, some suitable works were chosen for display in our Main Hall. The students brought their work on a Monday, when we are closed to the public, and worked with our technicians to install their work.

The cases got much of attention over the following few weeks and our visitors very much enjoyed seeing the displays. We’re sure you’ll agree they look great! Diolch yn fawr to the students for all their hard work, and to CSAD's Owen Stickler for organising the project.

Many of the books in the Library collections at the National Museum Wales have attractive decorative techniques applied to the covers or text blocks. Decoration on text blocks, the combined pages of the book inside the covers, is particularly lovely because it tends to be hidden when they are on the shelves.

The most popular examples of decorating text blocks include marbling and gilding. But one of the most interesting techniques is the one known as disappearing fore-edge painting, which was often hidden underneath the other types of decoration.

Fore-edge painting was a technique that reached the height of its popularity from the mid-17th century onwards. It was usually applied to the longest section of the text block, the one opposite the spine, the fore-edge.

Two books in our special collections feature examples of mid-19th century disappearing fore-edge paintings. They are the two volumes of the second edition of the Memoirs of Lord Bolingbroke by George Wingrove Cooke, and were published in 1836.

When the book is closed you cannot see the image, only the gilt edges of the text block, but when the leaves are fanned, the hidden picture is revealed.

To achieve this effect, the artist would need to fan the pages, and then secure them in a vice, this means they are applying the paint not to the edge of the page, but to just shy of the edge. Once completed, it is released from the vice and the gilding would be applied to the edges.

Landscape scenes were the most popular for this technique, and the ones on our books show Conway Castle and Caernarfon Castle.

Very often the motivation for a fore-edge painting was a demonstration of artistic skill, so it didn’t always follow that the images were related to the text contained within the book. These two volumes of Memoirs, do not have an obvious connection to the scenes painted. Lord Bolingbroke (Henry St John, 1st Viscount Bolingbroke 1678–1751) was an English politician during the reign of Queen Anne, and later George I, and is probably best known as a supporter of the Jacobite rebellion of 1715, but he does not appear to have any direct association with either Conwy or Caernarfon.

The volumes were acquired for the Library in 2008 from a rare book dealer, but we don’t know enough about their history to be able to tell when the fore-edge paintings were added. The first volume contains an inscription that states that the book was a gift to a T. M. Townley from his friend Samuel Thomas Abbot on his leaving Eton in 1843. Unfortunately we don’t know anything about either the recipient or the sender, so we can’t tell if one of them was ultimately responsible for painting the books.