Oxidation causes tips to have wettings issues. The oxidation will need to be removed with the FS-100 cleaning paste and brass cleaning wire. First, turn on the station and set the temperature to 320ºC or 610ºF. Once it gets up to temperature, dip the tip the FS-100 cleaning paste for about 2-3 seconds. Pull it out of the paste and let it sit for around 5 seconds. Clean the tip using the brass wire cleaner. Repeat the process until you have a shiny surface. Apply solder to the tip and make sure that it sticks to ensure that the tip has been cleaned properly.