Sebastiane Hegarty describes ˈtʃɔːk:
"In this series of sound studies, I continue to lend my own shell like to the fossil remains of previous seas. The Cretaceous samples employed include: Chalk taken from the bed of the River Itchen and from a recent cliff fall in Lyme Regis; fossilised ammonites that once swam in those deceased oceans and fragments of dinosaur eggs from nestings in France and Argentina (fragments which are now geographically distant, but were once tectonically close). These eight studies offer a sympathetic drift of attention away from chemistry and toward the extinction of substance and the audibility of loss.
Geologically, Chalk or calcium carbonate (CaCO3) is composed of Coccolith plates from millions of tiny single-cell organisms (Coccolithophores), which lived in the shallow prehistoric seas once covering now visible land. In fact the charnel remains of these creatures proffer microbiological proof for the existence and disappearance of such oceans. The Cretaceous Period from whence these tiny white skeletons date, some 60 to 145 million years ago, concluded with its own disappearance: the mass extinction of non-avian dinosaurs. In fact the geological clock that marks out time by the solid presence of stratified substance, simultaneously ticks with absence; one mass extinction event dividing the Jurassic from the Cretaceous and another the Cretaceous from the Paleogene.
2 HC2H3O2 + CaCO3 -> Ca(C2H3O2)2 + CO2 + H2O
The simple chemical action of dissolving chalk in vinegar permits acoustic access to a latent unheard geography, a sub-audible map of extinction. In this sonic dissolution of matter we hear not only the effervescent release of ancient gas, but also an audible escape from substance: a disappearance from weight, permanence and solidity.
In a number of the sound studies such loss is augmented, by allowing the sample to continue dissolving until it is exhausted, until the final breath of substance is taken. The sound does not extinguish by volume but by frequency, there is not a gradual quiet fade down into silence, but rather an acoustic and percussive crumbling of something into nothing.
Unlike the invisible microscopic algae that make up the substance of chalk, a fossilized ammonite presents a visually recognisable creature, a prehistoric form that once lived, but which geology buried away from time and preserved from disappearance. Dissolving these fossils seems like an act of vandalism, a destruction of history, an abolition of the past. But it also offers a temporal resurrection, a reanimation of the past into the present. Exhumed from permanence the past is allowed to dissolve and we can hear the immanence of nothing in everything, we can listen to the loss of substance occurring and the movement of solid matter into thin and ‘audible air’."