There is a significant difference in the particle sizes. Bigger, aggressive particles will sink to the bottom of the rinse bucket, due to the water softening properties of ONR. However, ONR will bind the small dirt particles, which float in the water, like in a colloid (verbal illustration only), onto the wash media - hence the rinse water doesn't look as dirty but the mitt does - and when you change the dirty media, you will physically remove those particles from the process. Yes, the mitt will look dirty but this dirt is not aggressive, as the critical grit sinks to the bottom of the bucket. ONR can bind the very small floating particles to the mitt, but I think it is more than obvious.