Poling-assisted bleaching was studied with respect to poling time, voltage, and temperature in glass samples having a gradient of silver nanoparticles across the depth. The optical extinction band due to the particles' surface plasmon resonance (around 415 nm) was measured and the Maxwell-Garnett effective medium theory was used to fit extinction spectra. Fitting allowed us to determine the evolution of the thickness of the near-surface layer where the particles' volume filling factor has dropped to zero as a result of the bleaching process. At 280 degrees C, bleaching started with a voltage as low as 200 V and saturated with time after about 1 h. Tight glass-electrode contact, voltage of at least 1 kV, and temperature higher than 200 degrees C were required in order to obtain significant and uniform bleaching in the poled area. The results were discussed in terms of the underlying electric-field-assisted dissolution of embedded metal nanoparticles.