Video: https://www.youtube.com/watch?v=QgYNCTiZKQs&t=473s
First stage of extraction. Dissolving the easiest materials. Acids and salts. It’s thick, heavy. Where most of the extraction happens.
Thick, dark, aroma. Fidelity on fruity notes, but the salts and acids give a tart and unripe feel. A smooth but sour cup.
Second stage. Simple and complex sugars. Sweetness.
Sweeter but without texture or clarity. Water with cane sugar. Still salty but very little acidity.
Final stage. Lighter color because most solubles are already gone. This is more watery. This is what happens if you brew for too long: watery and bitterness.
Much lighter, almost no aroma, no acidity and little sweetness. Dry and bitter. Florals, coconut etc are bitter elements and will extract here so we don’t want to get rid of it.
The goal is to determine how to change grind size to brew longer or shorter to control which extraction profile to reach on the brew to get a balanced cup. One usually wants the most sugars with enough bitter elements to complement the acidity. If you brew too short, the cup lacks in bitterness and the fruity notes become sour unripe. If you brew too long, fruity notes becomes mute with bitterness. This is the dialing of extraction.