So do you think this is just "scum" from body oils, dirt in the air, etc. that is being baked on in the constant sunlit areas? Or do I need to be more concerned about metals since I also have green haired blondes?

Any way to remove the metals that may be there, ie. copper, as to not cause the green hair syndrome? I've read some about the sequestering agents, but not sure what exactly has to be done and what the timing/order is. Is this a one time treatment, then followed be something else to remove the "bonded" metals, or do you try to keep them in suspension by continuing to add the sequestering agent on a continual basis?

I'll try the magic eraser and report back with the results.

I appreciate all the info!!

Clay