i have this happen with my kent also, to be honest the few times i saw it on the surface, i thought to myself that it must have been some residue from somewhere else, so i just dumped the bucket and rinsed it, it didnt happen again. my hunch, now that we are on the same page, is that it is something in the salt itself, and that it isnt that big of a deal. but if you call kent let me know!