The scale-up of thickening parameters from laboratory to industrial plant is still an open problem. Several techniques have been in use but none is free of criticism. In order to clarify these issue, in this work flotation tailings from one of the major Chilean copper mines was subjected to flocculation-settling tests with Orifloc-2010 polycarylamide in a Couette type reactor. By varying the shear rate from 100 to 2000 [s(-1)] the solid concentration from 1 to 15 [% by volume] and the flocculant dosage from 0 to 20 [g/ton] it was shown that an important interaction exists between these variables. At the optimal flocculant dosage, the optimal suspension concentration and the optimal flocculation time, an increase by 50% in the solid flux density function is possible when the shear rate of gamma = 100[s(-1)] is changed to the optimum value of around gamma approximate to 400[s(-1)]. (C) 2012 Elsevier B.V. All rights reserved.