After many years brewing coffee and searching the net for more info, I've finally found how to brew coffee my way that I really enjoy. I've broken all the standard ideas and rules, especially after seeing what Matt Perger & Scott Rao said about "over extraction". They basically argued that there is no such thing as over extraction. I thought about this for a long time and realized that if one was to brew a batch of "cold Brew" which requires at least 18-24 hours of brew time, Time must not be a factor in over extraction. It must be temperature related.
I have an electric kettle that will offer 96C which is a good temperature start for the extraction. I also use a stainless steel Bodum "type" unit that has a double thermal wall to maintain temperature. I pour hot tap water into this Bodum and when the water is ready, I pour this out and add the coffee. I then pour approximately half of the water, stir to soak and then pour in the rest. I insert the plunger but not into the coffee grinds to help maintain heat. After 2 minutes, I remove the plunger and gently stir the bloom to allow it to sink. I replace the plunger at the top. After 9-10 minutes, I again remove the plunger and scoop out the floating foam and other material with a large spoon. I then slowly plunge to the bottom.
The coffee is sweet with a lot of quality notes. There is no over extraction nor under extraction. In fact, I found that any bitter or sour notes comes from not enough brew time (Under extraction). The coffee can be finely ground rather than the standard Bodum coarseness. Too coarse and the brew time has to be extended. However, a longer brew time will only work if the temperature is maintained. Temperatures above 96C will extract unwanted flavours and this, is what I believe to be the most common reason for over extraction. I welcome any input on this idea.