Hey Peter,
Coach got some good responses from last week's "Back to Basics: Chemex" email. Several members of the Bean Team reported good results, a sense of clarity and there were some .... questions....about an issue or two that came up. I'm going to wait until the second half of this email to address those questions, because first I have to get to the question I brought up last week: What is a "clean cup" of coffee?

When Coach talks about a "clean cup," I'm talking about two things: One - Clarity, Three - Mouthfeel plus length of finish. Hey Coach, what happened to Two? I didn't forget it. Q-graders use "clean cup" to mean "free of faults and taints." Since Coach only deals with coffee rated in the Top 1%, two is a given, so I've left it out.

A clean cup typically has a lighter body, less viscous mouthfeel and has a short finish. A healthy dose of colloids (coffee oils), sucrose and "fines" in your cup will tend to feel heavy on your tongue and will usually carry more earthy flavor notes such as chocolate, caramel, tobacco, leather etc. Those heavier notes can overpower the fruit and floral nuances that you would have noticed more easily if the colloids and fines were reduced (the cup were cleaner). A clean cup doesn't linger as long on the palate either.
Brewing dirty or clean. To a degree, you can change the cleanliness of a coffee by the way you brew. More colloids and fines slip through a metal filter than a paper one. Brew with a press pot to amp up the earthy notes. Want a super clean cup? Brew with a Chemex. Their filter paper is 30% thicker for two reasons: One, so that the filter won't collapse into the pour spout during brewing and two, to get a cleaner cup by trapping more fines and colloids.

Now for a couple of very quick answers to the most common Chemex brewing questions: