Abstract: A system for detecting a defect in a membranous article (20) comprising: an emitter probe (10) connected to an electrical supply (14), said probe (10) insertable into a cavity of said article (20); a sensor (15) for receiving an electrical discharge from said probe (10); a conveyor system for bringing the probe and sensor into mutual proximity; a processor for measuring the potential difference between the probe and sensor, said processor capable of detecting a defect based upon said measurement.