Jorge, you may have a point. It is claimed that alkaline fixers reduce the problem of overfixing, and if I understand correctly, this is because they do not reduce the stain, which is part of the image, and they do not dissolve image silver (i.e, alkaline fixers should only dissolve undeveloped silver) in the way that acid fixers can with excessive fixing times. Is this claim true?--I'm not sure, but I think this is the basis of the claim.