Re: Pan Heating
The mercury ball of water is what you are looking for. You are right though, that the "before it's hot enough" and the "after it's too hot" do look similar, but it's just a matter of time. When a pan is too hot the water bubbles splatter and spread out quicker, and the there is sometimes a bit of smoke or instant steam from the water hitting the hot pan.
If you watch the pan and test it a few times as it heats up you should be able to know when it is still not hot enough, then as soon as you hit the "water ball, or mercury ball" stage you are good to go.
Thanks for your feedback and we are glad that you found the lesson helpful. If you have anymore questions, feel free to ask away.