This paper presents flotation results carried out on fluorite ore using a relatively short column, operated under negative bias regime and without wash water. The term short column is used from a kinetic point of view from which collection zone comes out to be around 8 m tall (the relation height/diameter appears valid for industrial size columns). Negative bias was achieved making tailing flow smaller than feed flow. Hence, part of the water is carried up within bubbles wakes. No wash water is added. It was found that, heavily loaded bubbles, formed in high-grade fluorite pulps, at negative bias, levitate easier than positive bias. Under such conditions, carrying capacity of columns seems to increase due to a decrease in downward velocity of pulp. Recovery increases considerably, resulting in a sort of rougher flotation. High recovery as well as grades was obtained under negative bias regime. (c) 2006 Elsevier Ltd. All rights reserved.