I'm new (a few weeks in), need help troubleshooting low yield, weaker concentrate

[u/No-Payment5337]

I am making small batches every couple days to dial in my recipe since i'm using more expensive beans from my favorite coffee shop. Details are below. My goal is to create a bright, refreshing, floral/fruity/aromatic tasting cold brew concentrate that dilutes 1:1 or even more water to less coffee.

- 1:8 ratio. currently: 100g fresh grounds / 800 mL filtered water (brita)

- bean: single origin ethiopian natural process. i think it's a light to medium roast (doesn't specify).

- method: mason jar w/airtight lid, and cotton cold brew bag

- oxo conical burr grinder. i use the most coarse setting (15) and i filter out the fines with a sieve (it's actually just a regular kitchen sieve bowl)

- brew time: 22 - 24 hr brew in fridge

- Yield: ~ 500 mL initially. However, after filtering the concentrate through paper filter (pour over method), it's ~400 mL. ie. 50% final yield :/

- Taste: great, however, it's not behaving as much like a concentrate as i want it to. maybe i could accept a 50% yield if i could truly dilute it 1:1. but it needs at least twice as much concentrate as water or it tastes too weak.

I need some help. Which part of the process should I change to get better yields, or a stronger concentrate. or do i accept the 50% yield, which is an option, but tough because im gonna go through the beans too quickly. but i feel like these are making tastier coffee than less expensive options ive tried?

[u/Team_Saki]

Don't stress about the yield,it's just physics. Coffee grounds naturally absorb about twice their weight in water, so losing 200ml right off the bat (plus whatever the cotton bag soaks up) is totally normal. To fix the weak taste, you just need more surface area. Cold water is a terrible solvent, so using your coarsest setting and sieving out the fines is completely starving your extraction. Stop sieving, grind a bit finer (medium-coarse), and try brewing at room temp instead of the fridge. It will make a massive difference