Sub-parallel concentric conic fractures can be produced consecutively in Perspex by liquid indentation. There is a linear relationshp between the conic angle, , of Hertzian fracture and the Poisson's ratio, , of the material. This angle is about 10 higher than the calculated path of the principal stress trajectory for a given . decreases with the increase of stress application rate. This dependence of is very marked in materials with high Poisson's ratios.