I opened up an old soldering iron and when I took out the tip, I found this substance underneath that even comes on my hand if I touch it. What is this? Is this still suitable for use?
Note- I really couldn't find a way to search this thing so forgive me if it's a duplicate of some sort.
Addition : I removed the tip and saw this -
Is this still good enough to use or should I replace the tip?
The tip heats up but solder won't stick and tip is just black.
I could clean it upto this level -
Why does it have a bluish tinge @ some places?