It wasn't too hot. The iron was touching the board for too long a time. It was touching for too long a time because the iron wasn't hot enough to melt the solder quickly.
The goal is to ZAP the solder quickly. Higher wattage, temperature control, electrostatic discharge protection are signs of a quality iron. An iron with low wattage, no temperature control, no ESD protection are signs of an inferior iron. Quality irons zap the solder quickly. Inferior irons do not.
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