JHCCoffee But I could use a refresher on how to vary flow rate (ml/sec) during each phase of the pour to impact taste. What are the impacts of slower versus faster flow rates? What do you aim for, when? To be clear, this is the ml/sec I see on my scale, as I pour, as distinct from the overall average flow rate for the pour (ml poured / by time in seconds).
What is your brew size?
At the moment I cannot recommend a V60 02 compatible filter paper, hopefully I will be able to in the next week. (I’m currently using the pink & black loose bagged 01 Japanese papers in my 02 Switch).
I cannot advise regarding a flow rate as seen on your scales. I would concentrate on hitting the pulse weights and timings based on the weights & times that you see in real time, as you pour. I wouldn’t recommend a regime that was reliant on specific technology, because it then becomes less easy to share.
May I ask why your pre infusion pour is larger than your subsequent pours?
I wouldn’t bloom for that long. I would aim to keep pour timings and pulse weights consistent for ease of committing to memory.
Faster pour rates (for a fixed grind setting & brew size) extract less, assuming that you are not too fine to start with and under-extracting due to this fine grind.
For my 1 cup brews (200-210g) an average flow rate of around 1g/s seems to give good results & extractions, so I often pour at an average of 1g/s (e.g. 40g poured at 40s intervals, each pour taking 15s).
If cups are under & lacking in body, I would use smaller pulses like 33g every 30s, or 25g every 30s (pours taking 10s each).
I would start with roughly ⅓ of the pours in the centre of the Drip Assist for V60, the remainder in the ring, to agitate & wet at the start of the brew, then less agitation later in the brew to keep silt levels down.
If your grind is too fine then you may have excessive silt/filmy mouthfeel in cups, if so grind coarser until the mouthfeel is to your preference & correct the pour rate to get extraction back on track.
Astringency is not a good way to tune brews. Over-extraction is a very specific, smoky, sickly, cloying dryness. It’s easy to fix by grinding coarser, then it is very unlikely to ever happen again (except for extremely rare coffees that extract unusually easily…for these I would recommend immersion brewing).
So, once you have fixed over-extraction issues, what do you do when you still get astringency? It could be excessive silt in the cup, or it could be darker, drier flavours coming to the fore because you have extracted just a little bit too little. It could even be that you have bought a drier tasting coffee (this is where scoring cups/bags, against a known brew regime becomes useful for sense checking compared to normal results).
JHCCoffee Taste is a personal thing and so there is no right or wrong.
Preference is personal (we buy different coffees because we want them to taste different, but we expect to brew those different tasting coffees consistently, minimising generic failure states), but to achieve an objective target & repeat it (whatever that is, is up to you), requires you to carry out the actions (brew inputs) that will meet that result.