@juliank I'll tag in @neal for a more authoritative & informed perspective, but I'd advise..:
1. 20g (because it's easier to hit that dose with an uncooperative scale)
2. 1:18 coffee:water ratio, so 360g water; use Third Wave Water or something similar if you have the option
3. Pre-heat the V60 _aggressively_ for a light roast, especially if it's a ceramic one, or glass; aim to brew @ 96°C
4. +40g in, ~30s degas, stir
5. +140g in, swirl, → ~1m30s
6. +180g in, swirl, → ~3m
@juliank @neal for the lighter roasts I've found brewing a larger dose at the same ratio works better (so 1:18 → 20g:360g works better than 10g:180g), possibly because there is more thermal mass so it cools more slowly? In any case it seems to come out more aromatic and tastier.
And the preheating I found to be crucial. Not just a good rinse, but actually submerging the dripper until it gets quite hot indeed.
@gnomon @juliank Right, the amount of coffee is the thing that really sticks out here. For the amount of water initially used there, 19 grams gets you closest to general guidance. It's always better to err on the side of too much coffee as you can always water it down after the brewing is finished so maybe try up-dosing until it stops getting better.
@neal @gnomon I think it turned out to be 260ml brew with 18g of coffee + 40 ml bypass; the scale crapped out a bit:
- I filled in 18g, it then went down to 15g in 5s steps...
- I started 2nd pour did not notice the scale turned itself off.
So I measured output at 260ml, and added 40ml of water. Came out ok.