A method for eradication of accumulated background on Ilford C‐2 plates, 100–200&mgr; thick, without reducing their sensitivity to medium ionizing particles, is described. The method involves a mild oxidation of the emulsion by air saturated with water vapor at 35°C for a period of about 16 hr. The plates are then dried and are ready for experimental exposure. Analysis of grain counts shows no loss of sensitivity in proton tracks over their last 200&mgr; range when the plates are developed with a mild hydroquinone developer. Complete eradication of background alpha‐tracks and stars is secured as well as destruction of latent images of the less ionizing proton recoils instigated by external neutron bombardment. Grain density studies on proton tracks located at different depths in the emulsion indicate substantially uniform sensitivity after eradication except for the uppermost 50&mgr; which develop with about a 10 percent reduction in mean grain density as compared with tracks deep within the recording medium.