Commence ye olde H20 boil. If you're using a fancy kettle with temperature readout, set the temp to 209°F (science side-note: the boiling point of water at sea level is 212°F). If you're using a stovetop tea kettle - just let it start screamin' and hissin', you'll know when to take it off.
Meanwhile, prep the other goodies:
Weigh out 45 grams of coffee, and load it up into your grinder (don't grind just yet, you'll want to wait until just before brewing. Once exposed to oxygen, coffee starts losing it's awesomeness in a matter of seconds).
Open your Chemex paper filter into a cone shape so that one side of the cone has three layers (this detail is important), and place it into the top of the Chemex brewer. The thick (three-layer) portion should cover the pouring spout.
Once your water has boiled, we're going to "pre-wet" the filter area of the Chemex. The goal here is to remove any type of paper taste... as well as pre-heat the brewing device. It's typically not ideal for hot coffee to encounter cold glass, so we have a double-whammy here. Remove the lid from your filter after successfully pre-wetting the filter to allow the temp to cool to our ideal range (202-205°F range).
(Side note: much of the country is still in a massive drought. Don't be a doofus by taking this pre-wet step too seriously. It can totally be skipped ... and if you do it, use the minimal amount of water that you can)
Next, empty out the water from the pre-wet step (you don't need to remove the filter in order to do this. Part of the genius design of the Chemex, it will simply flow out that glass groove and the filter will remain in-tact).
Grind your beans: like other pour-over methods, you'll want a fine-medium grind for the Chemex. Somewhere in the "middle" of the grind settings if you're using a Baratza ... and if you're winging it, just go with something that's between beach sand + sea salt.
When your water cools to around 202-205°F, you're ready to brew. Put the lid back on your kettle, dump the coffee grounds into the Chemex, and have your timer ready. Make sure your scale is reset to zero with the Chemex + coffee resting on it. The remainder of this process (the actual brewing of the actual coffee) is pretty dang straightforward. The first bit of water you'll be adding makes up the bloom - a process in which the coffee grounds release all the remaining CO2 gas and (incredible smelling) oils from the roasting process. Ground coffee will hold approximately 2x it's weight in water, so you'll want to dump about 90-120 grams of water for this process. Make sure to start your timer the moment the water makes contact.
There's debate in the coffee world for how long your bloom time should take. You'll read anywhere from 30 seconds to a full minute. In general, we like to bloom for the full minute. Make sure to get your nose right up in the wet grounds during this step (it really should smell magnificent).
After your 1 minute bloom time, you'll begin to pour the remaining water in a slow, circular fashion (focusing more on the "middle" of the grounds rather than dumping water around the glass rim of the Chemex) until your scale reads approximately 400-420 grams. With a standard pour-over for one person, you'll generally be aiming for a 3-3:30 minute brew time. Since you're making two cups here - the total brew time might be closer to 5 minutes.
With that target brew time in mind, you'll 'temper' the rest of your water pourin' based on how fast the coffee extracts through your grounds. We generally try to pour the coffee in 3 'batches' after the bloom: first to around 400-420 grams, second to around 550 grams, and last to the final 675 grams.
If your coffee isn't extracting quickly enough: meaning, it's just barely flowin' out of the top - don't panic. Simply grab both pointy ends of the Chemex filter and gently raise it up and away from the glass. You'll notice a much quicker flow right off the bat. Sometimes this is the only adjustment needed to "catch up" to your ideal brew time (you can lift it out and gently place back in, and should notice a quicker extraction). This likely means that your grind was too 'fine' and you'll need to adjust your grind a few clicks in the opposite direction (for a slightly courser grinder). This should do the trick next time.
Discard the filter + grounds, grab a couple mugs (and another human), and enjoy! Please don't hesitate to contact us with your brewing questions - just send a note to firstname.lastname@example.org and we'll get back to you promptly.