(see hardware section), Digital kitchen scale, Burr coffee grinder
I’m just going to say this once: BE CAREFUL. We’re hacking soda bottles with a box cutter here so take precautions, go slowly, and always cut away from anything that can bleed. There, I said it. Also (and I hope obviously), don’t let kids attempt this.
Set the blade of the utility knife so that it’s sticking about a quarter of an inch out of its handle and cut the bottom 3 inches off both soda bottles. Discard the bottoms. Remove the bottle lids. Cut an asterisk-shaped hole in the first lid. (Try doing this with the cap upright rather than upside down. AND BE CAREFUL.) Use the thumbtack to poke a tiny hole right in the middle of the second cap. Screw both caps back onto the bottles. Wad up the cheesecloth and stuff it into the neck of the bottle with the asterisk-shaped hole.
Place the bottle with the asterisk-shaped hole on top of the pitcher with the cap facing down and secure with the rulers and rubber bands. Place the coffee grounds into the large paper filter and set inside the bottle. Set this entire apparatus on top of a digital scale. Zero the scale, then slowly pour the water in a spiral over the grounds to bloom the coffee. This step should take about 30 seconds. Top with the small coffee filter, which will act as a diffuser.
Nestle the bottle with the tiny hole, cap-down, onto the bottle holding the coffee.
Zero the scale again and weigh the ice into the top bottle. Set your tower out of direct sunlight until all of the ice has melted and passed through the coffee, 10 to 12 hours. If you’re keeping an eye on the coffee-brewing process, you should see one drop of water moving through the coffee about every 7 seconds.
Once the coffee is done brewing, remove the rig from the pitcher and discard or compost the coffee grounds. Serve immediately over additional ice, if desired, or transfer to an airtight container and refrigerate for up to 1 week.
If you want to be a purist, you can bloom the coffee using cold water, but, in my opinion, the hot bloom method tastes better.