The influence of path length and slurry velocity on the performance of a reciprocating canister type super-conducting magnetic separator has been investigated. The canister train of a Carpco 5 T separator was removed and replaced with seven test cells each with a different length of stainless steel matrix, varying from 25 to 500 mm. A kaolin sample from the St. Austell area in Cornwall was dispersed and pumped through each matrix. The resultant product was analysed for iron. The longer the path length, at a fixed flowrate, the greater was the removal of iron from the kaolin. Shorter path lengths, however, offer the potential advantage of multiple paths within a canister of fixed length. The optimum path length for the kaolin was found to be within the range 25-100 mm, depending on percentage iron removal. The optimum path length increased as the required iron removal rate was increased. Increasing the slurry velocity through the matrix reduced particle capture, with the effect being more significant at 2 T than at 5 T. The higher throughput achieved at the increased velocity however more than compensates for the reduction in performance. (C) 2002 Elsevier Science Ltd. All rights reserved.