Heap leaching has significant challenges associated with permeability. Low permeability decreases recovery rates and recovery. It is believed that low heap permeability is caused by the migration of fine particles. This fines migration clogs the natural flow path of leach solutions, forcing it to flow around some regions of the heap, leaving them un-leached. Binders show significant promise in this application because they will increase agglomerate strength leading to a reduction in fines migration. However. most binders have been used without any systematic reasoning. Using a novel soak test, systematic Studies have been completed on a wide range of binders. A nonionic polyacrylamide was found to reduce fines migration as much as 93%. It is believed that this binder was successful due to electrostatic attraction, hydrogen bonding, and physical bonding. (C) 2009 Elsevier B.V. All rights reserved