Hey

A local coffee shop told me that when you get the coffee to look like a upside down dome on a syphon coffee once it has extracted it means that you have had a good extraction. I cannot see how this is true, am I wrong?

Thanks in advance
Craig

I've read this before somewhere, not sure where. If you gently stir the coffee as it's being sucked down you can get a very nice dome. I'm not sure why this might indicate a better extraction; maybe because every last drop of flavour is pulled from the grounds as the vacuum packs them tightly around the filter. That's my unscientific guess, anyway. It certainly looks very satisfying when you're done, and it makes it easier to empty and clean the funnel.

This is from Scott Rao's book Everything But Espresso. He advocates for a mild dome on both syphon and cone-shaped drip. The principle he invokes is that every path from the surface of the coffee bed to the filter should be equal in length, in order to achieve even extraction. Since syphon filters are typically smaller in diameter than the surface of the bed, a flat bed would mean that the coffee percolating through the perimeter of the bed would have a longer path to the filter, while a mild dome compensates for this effect by decreasing the distance between the perimeter of the bed and the filter.

craigcharity wrote:Hey

A local coffee shop told me that when you get the coffee to look like a upside down dome on a syphon coffee once it has extracted it means that you have had a good extraction. ...

Craig

I think experts overthink both syphon and pourovers. Good extraction is important and you can discern it in the cup. Minute details that all of us go into (self included) are sometimes over the top.

With syphons, I think it is important to let bloom. I then push the grounds down once to ensure full saturation (I never stir as it creates issues for draining with the glass rods) Dome? Not worried about it.

The advice on stirring to get a dome is aimed at the cloth filters, as Bold|Java stated, when using a glass filter rod, you avoid stirring and simply dunk the grounds after the bloom for best extraction.

I would amend that to say stirring is aimed at cloth and paper filters.

(What I do for 18g coffee and 250g water): After the gently boiling water rises into the upper chamber, I pour in the grounds, then immediately start the timer and push the grounds under the water level with a small wire whisk to ensure that all the grounds are wet. After 30 seconds of steep time, I turn off the heat and remove from the halogen heater (or remove the butane burner.) When the coffee begins to drop, I give the grounds a gentle quick stir, just enough to break up the bloom and start a gentle vortex. Depending on the coffee and grind, the draw down takes about a minute with a paper filter.

FWIW, I believe the coffee tastes better when I get a nice, shallow even dome than it does when the dome is very tall or irregular, or grounds have migrated up the sides of the upper chamber.

I always get nicely rounded domes when brewing in the Aeropress with Tim Wendelboe's method, which mimics the stirring typically done on syphons just before the "drawdown":

http://vimeo.com/16261120

With Dave and Craig on this one. I cannot see how this is true either. It strikes me as one of the more absurd claims I've encountered in relation to coffee brewing.

The extraction during syphon brewing occurs during the percolation and draw down phases. What really affects the brew is dose, grind, percolation time, and degree of agitation during percolation. What happens during the last couple seconds of the draw down is dwarfed by these other factors. If some of the grind ends up 0.5 cm closer to the filter or whatever, all during the last couple seconds of the draw down, so what. The extraction is already finished, move on. Hand waving is not necessary if you've got your dose, grind, and percolation parameters set right. Just enjoy the coffee!

But if one likes the shape of a dome (it is purdy, I agree) then by all means go for it. It's a well known fact that when food looks good it tastes better!

I think a blind test is in order. I will report back as soon as I have done it.

Good idea, I'll try a blind test also. All these claims do make me curious.

But I am prepared to eat crow: In blind testing, if anyone notices a real improvement or has a genuine preference (let's say 7 out of 10 times) from having a gentle dome (from a little stir during draw down), as compared to drawing down without the stir, all else being equal, I'll send you my Hario Nouveau, shipping included!