As a subject matter expert in metallurgy, I can tell you that the phrase "When the iron is hot" is often used metaphorically to suggest that one should take action while conditions are favorable, much like one would strike a hot iron to forge it. However, if you're referring to the actual process of working with iron, it's important to understand that iron can be worked at various temperatures depending on the specific task.

In blacksmithing, for example, iron is heated to different temperatures to achieve different results:
- Yellow heat: The iron is warm and workable but not yet fully malleable.
- Red heat: The iron is now malleable and can be shaped with a hammer.
- Orange heat: The iron is very soft and can be forged more easily.
- Blue heat: The iron is at its most malleable and can be drawn out into thin shapes.

Each stage requires careful control of the heat to ensure the iron is neither under- nor over-heated for the task at hand.

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(metallurgy, blacksmithing, literally) To strike a hot piece of metal, especially iron, with a mallet or other tool before it cools, while it is still hot enough to be shaped. (idiomatic) To act on an opportunity promptly while favorable conditions exist; to avoid waiting.read more >>