A project to conserve, cast and repackage a collection of Jurassic ammonites from Dorset was undertaken at Amgueddfa Cymru - National Museum Wales. The specimens are all either cited or figured and include holotypes and paratypes. Many had been consolidated 40 years ago with the acrylic resin Bedacryl and some were embedded in plaster. The Bedacryl had become tacky with age and dust that had settled on it was difficult to remove. Pyrite is present in the rock and the fossils and many of the ammonites were affected by pyrite decay. The specimens were cleaned, treated for pyrite decay if required, re-consolidated and packaged in protective microclimates. Due to the scientific importance of the collection, casts were made of some of the ammonites to ensure a good record of the specimens, in case of further deterioration of the original specimens. Following re-consolidation, silicone moulds were taken of the specimens and from these, casts were made. It was important that the casts should be free of even microscopic bubbles, and after some experimentation it was found that the addition of the antifoaming agent Simeticone significantly reduced the number of bubbles in the casts.
