An extensive aging study of bakelite Resistive Plate Chambers

We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility, on two bakelite Resistive Plate Chambers (RPC) detectors. With a method based on a model describing the behavior of an RPC exposed to a large particle flux, we have periodically measured the electrode resistivity rho of the two detectors over 3 years. We observed a large increase of rho with time, from initial values of about 10**1**0 Omega cm to more than 200 multiplied by 10**1**0 Omega cm. A corresponding degradation of the RPC rate capability, from about 3 kHz/cm**2 to less than 200 Hz/cm **2, was observed. The reversibility of the process, using a humid gas mixture, has also been studied.