chapotraphouse

You can get good Iced coffee that way, but you also have to do something to boost extraction. I usually grind a little bit finer and stir the grounds a bit while they're brewing. It's a lot easier with something like a Chemex or a Kalita Wave since they already drain fairly slow.

As for the cold brew, it's hard to give an exact recommendation without knowing what coffee you're using, what your water is like, and what equipment you have on hand.

In general what I do on a smaller scale is:

• Using a paper cold brew bag inside of a nylon one (just in case the paper one breaks). You can use a cotton bag but they're hard to care for.
• Grinding the coffee aiming for like a 800-1000μm mean particle size, which is a medium/medium-coarse grind about what you would do for a large commercial batch brewer. This is significantly finer than almost every cold brew recipe online will tell you.
• Using roughly a 9:1 water to coffee ratio. This is significantly more water than any recipe will tell you.
• Doing a "hot bloom" where you start with about 1/4 of your water hot and you agitate the coffee and the hot water together for about 45 seconds to 1 minute before adding the rest of the water as either ice water or very cold water as quickly as you can.
• Brewing in a fridge for roughly 18-20 hours. You can start tasting at around 16 hours and it's usually fine to let it go up to 24 hours.
• Remove the bag and jury-rig some way for it to sit above the cold brew and drain for about half an hour.
• Dilute the cold brew to taste, usually by about 1/4.
• Optional step of letting the cold brew sit for an hour or so and then carefully decanting into a separate container, leaving any silt that has settled at the bottom of the original container. This will give you a clearer final drink and a bit longer of a shelf life.

The exact ratio and brew time will depend heavily on your coffee and your water. The biggest problem I see (taste) with the water people use is too high levels of anything acting as a pH buffer in the water, you can't really do anything about this without building your own water (starting with pure water and adding minerals), this always hides any of the delicate flavors of the coffee and gives the cold brew a very strong prune-y note.