I don't recall ever having the problem with the iron before, but it's been a few years since I used it, as I'm just getting back into some projects since my Electronics degree.
I bought some solder for a new project (I need a lot) and it's lead-free:
95% Tin 4% Silver 1% Copper
Now, I'm not sure how tolerant the values are for melting point but I can say that it does appear to act Eutectic, like the known combination 95.5/4/0.5 (Indalloy 246) which has a melting point of 217 degrees Celcius.
According to the manufacturer of my Iron (Antex) it has a tip temperature of 370 celcius.
I sanded down the tip yesterday with a fine grain metal sanding paper to see if the tip just needed cleaning, however it's now gone "black" instead of the shiny silver it was when I first sanded it.
The real question I wonder is where the problem lies, is it that my tip is dead, is my iron too low power or is it just that my iron is dead.
I ask because I need to know whether to replace the iron, the tip or a higher power iron. My preference is to stick with the Antex irons, and I prefer "precision" bits like the on in my current iron, so, what are the recommendations?