We study the collective behaviour of a close-packed monolayer of non-Brownian
particles at a fluid-liquid interface. Such a particle raft forms a two-dimensional elastic solid
and can support anisotropic stresses and strains, e.g. it buckles in uniaxial compression and
cracks in tension. We characterise this solid in terms of Young’s modulus and Poisson ratio
derived from simple theoretical considerations and show the validity of these estimates by using
an experimental buckling assay to deduce Young’s modulus.