Conventional polishing process variables such as down force, platen speed, slurry flow rate, etc. tend to be both coupled together and indirect. Within this context, one might argue that the net rate of slurry admission or concomitantly, effective volume of slurry between the substrate and pad is a direct process parameter, which is affected by polishing pressure, substrate-pad relative velocity, pad wear and texture, etc. In this work, the role of slurry admittance is investigated by direct control of interference between the pad surface and the carrier retainer ring. Both fixed and dynamic implementations are investigated. Observed patterns of material removal on substrates polished with a fixed orientation are correlated and discussed.