I have been brewing an El Salvador and a Sumatra Mandheling alternately, in my Krups Moka Brew (which shows the bloom). The El Sal has lottsa bloom and the Sumatra has hardly any.
They were both roasted 15 seconds into the 2CR and rested for 4-5-6 days.
JP, you're prolly right on the miscalculation. I did just check with 60 deg F water, my clear plastic AP is around 302g of water.
I've done other checks with finely ground 2-day post grind coffee with no bloom and nearly (15 second) settling. If it sinks in water, I reasoned it's got to be more dense. The particles also respond beautifully to centrifugation. Obviously, some of the initial bouyancy is due to co2 bloom, but that's only the beginning of the steep.
When I measure dry coffee, I'm always surprised that the beans and unpacked grounds are similar volume. Once you mix them with water, though, the coffee grounds particles must be close to coffee/water density (very close based on a couple of checks in the past) - once they are waterlogged.
Jkalpin is right, bloom is dependent on roast level, grind level, degree of green and roasted aging, and type of bean. I haven't had consistent results so I can't personally conclude that one varietal is more bloom-prone vs others given same roast parameters, but there is significant variation and I've just done bloom suppression to take that variation out of brewing process.
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"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
You just multiplied by the density instead of divided. I made the exact same mistake (twice in a row) the other day.
Netphilosopher Said:
I've done other checks with finely ground 2-day post grind coffee with no bloom and nearly (15 second) settling. If it sinks in water, I reasoned it's got to be more dense. The particles also respond beautifully to centrifugation. Obviously, some of the initial bouyancy is due to co2 bloom, but that's only the beginning of the steep.
According to Illy, "typical" espresso is 1.02 g/ml with 53 mg/ml solids. That implies a coffee solids density of 1.6 g/ml (or 0.62 ml/g). I'm not sure if that includes the lipids.
What I thought to do was add coffee grounds to water topped up to a precise volume. Then the weight would give me the density of the solids. But when I tried this with cold water there were all of these little tiny bubbles in the mixture that were very persistent. It looked like a flask of Guinness. With all that extra gas and the buoyed up grounds and foam what I initially came up with was 0.8 g/ml. Then after stirring and waiting half an hour it was 1.0 g/ml. Another half an hour and it settled at around 1.3 g/ml.
I tried it again using hot water. After the water cooled there was no gas and very little crud on top. I topped up the flask and got about 1.4 g/ml (0.74 ± .05 ml/g).
But I was wondering how different are the densities of the soluble and insoluble fractions? And might there be a significant volume contraction when the coffee dissolves? Those tiny gas bubbles sure displaced a lot of water.
I was kind of hoping it was something you'd explored. I'll bet you have a fat notebook filled with interesting observations about coffee.
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