During the interaction of obliquely incident microwaves with an unmagnetized inhomogeneous laboratory plasma, the Langmuir wave energy is observed to narrow spatially and to rapidly grow to its peak value followed by a sudden collapse. This phenomenon has been referred to as the 'Soliton Flash' and occurs at rather high intensity microwave radiation (P0>or=600 W, eta 0=E02/8 pi n kappa T>or=4*10-3). The observed flash can be interpreted using the wavebreaking model, and the electric field strength at the wavebreaking time has been estimated by several methods, these methods showing reasonable agreement.