  Sandstone mechanical stability is of key concern in projects involving
injections of CO2 in sandstone geological reservoirs, for the purpose of
long-term storage. We developed a method to measure nanometer-scale
deformations of sandstones in real time. We demonstrate that Berea sandstone,
when hydrated, changes dimensions with a relative deformation of the order of
10^(-4). If the moisture content increases, sandstone samples exhibit an
extension and if the moisture content decreases then the samples shrink. We
also discover that, immediately after exposure to water, the sandstone
temporarily shrinks, just for a few seconds, after which a slow extension
begins, and continues until about half of the fluid evaporates. Such shrinkage
followed by an extension has been observed also when the sample was exposed to
acetone, Mineral Spirits or Vacuum Oil. The results are obtained using a
high-resolution nano-positioner technique and, in independent experiments,
confirmed using the technique of coda wave interferometry.
