Typical third wave coffees are lightly roasted and harder to extract. It the roast was a little off, it will be even harder to extract (this happens often, unfortunately).
Have you tried a dark roast? Starbucks might have just what you need. I think it is fairly easy to get extraction numbers much higher with a dark roast compared to your typical bleeding edge light roast.
jpender Senior Member Joined: 11 Jul 2011 Posts: 732 Location: California Expertise: I like coffee
Grinder: OE LIDO Vac Pot: S/S Moka Pot Drip: Aeropress
Posted Fri May 18, 2012, 8:14am Subject: Re: Calling All VST Refractometer Owners - A Brewing Challenge:
I don't have a VST refractometer (or a press pot for that matter) so I'm technically disqualified. I also suspect that Netphilosopher has tried this at least half a dozen times in his Coffee Research Utility Kitchen, so it's probably near to impossible if not impossible.
But I made a half-hearted attempt anyways. I bought some pre-ground coffee while traveling last month that I don't like at all. It's sitting in the freezer for just this sort of thing.
I added 36.0g (it's a drip grind) to 175g of hot water. Simmered and stirred in a saucepan for 8 min. Poured into inverted Aeropress. Used enough additional hot water to rinse coffee from pan and utensil into AP and top up to 236g total slurry weight (18% brew ratio). Pressed.
148g beverage, 87g wet grounds (1g went missing).
Dried the grounds in the oven for a little over 2 hours until weight stablized. Cooled: 29.8g That's a yield of 17.2% and a beverage strength of 4.2% (including some undissolved solids).
Not even close.
By Netphilosopher's theory the effective extraction was only 24%, less than what I'd have guessed I'd get by boiling grounds for 8 minutes.
Now the really weird thing is that although the coffee was way too bitter, it was also delicious. I drank it.
GlennV Senior Member Joined: 27 Oct 2011 Posts: 29 Location: UK Expertise: I love coffee
Posted Sun Jun 3, 2012, 1:51pm Subject: Re: Calling All VST Refractometer Owners - A Brewing Challenge:
I did had a go, with a criminally over roasted sidamo, espresso grind, 8 mins in a bain-marie to keep the temperature up, and it only got to 4.6%. Underextracted by all the usual formulae using a 2g/g water lost or retained ratio - I didn't dare taste it! I do find the argument for using all the brew water for extraction yield calculations, for immersion methods, pretty compelling. What I don't understand, though, is how this squares with the fact that those with far more tasting experience than me are recommending 19-20% yields for both drip and immersion methods, with the usual formulae. For example, the Nick Cho video on youtube showing his clever dripper technique would come out at about 22% yield using all the brew water for the calculation ("Gold + Paper + Clever", which is certainly a full immersion technique as he pulls the grinds out of the brew in a Gold filter before the drawdown).
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