I have this black junk building up on my clothes iron.
What is it? Maybe the detergent/fabric softener are leaving a residue that the iron is picking up? And how do I get rid of it? My usual method, ironing a pure white shirt, only gets off enough to ruin the shirt. :mad:
Try ironing over a paper bag sprinkled with salt.
You can also scrub it with a scour pad and a bit of dishwasher detergent, but if it’s a Teflon-coated iron, mind that you don’t scratch it.
I’ll let someone else tackle the “what is it”. 
Sounds like you might have hard water, with some minerals in it. You might want to buy some distilled water to use when you iron.
Mineral accumulation is usually hard and white, while black stuff that comes off on clothes is probably organic. Either way, though, soaking in white vinegar would probably help.
Yeah, I don’t think it’s minerals…it doesn’t have a crystalline look to it. More like if you had adhesive on the iron, then heated it.
I think I’ll try cleaning it but frankly it’s become a PITA. I went out and bought a new one. @$80 I hope it won’t have the same problem.
Any time I’ve ended up with blank gunk on my clothes it’s because I’ve accidentally applied a too-hot iron to a cotton-poly blend.
That may explain it. I do iron with it full-tilt. I think I’ll back off on the heat, watch how the new iron responds.
Really? I don’t have black stuff on my iron, but occasionally I gunk it up when using fusible web. Ironing over a fabric softener sheet takes care of the gunk, but I don’t use softener sheets, so next time I’ll try the paperbag-salt thing. 
My problem is lime build-up from our water. I have to do the vinegar thing regularly or no steam.