Spiral concentrators are widely used in the iron ore industries to concentrate heavy iron oxides from light silica gangue minerals. The operation of a WW-6 spiral for the concentration of an iron oxide ore is analyzed through the size recovery or partition curves of the minerals. Several tests conducted following a factorial design using wash water addition, feed rate and slurry solid concentration as studied factors show that for the tested conditions the wash water addition has the most important effect on the spiral performance with its effect being mainly located on coarse particles. (C) 2014 Elsevier B.V. All rights reserved.