Postby Javier on Tue Jan 01, 2013 2:04 pm
I just pulled a shot of Sweet Maria's Brazil Fazenda do Sertao:
Line pressure - 3.25 Bar
Boiler pressure - 1.25 Bar
Dose - 18 grams
Preinfusion - 6 seconds
One pull
Time, before thinned and blonde crema - 20 seconds (from first drop)
Espresso - 21 grams
*EDIT* Volume - 30 ml

Here Javier is brewing close to 100%, with a grind fine enough so that it takes 20 sec to pour. With 30 sec it would probably be around a 50% ratio.

It's also good to report the coffee too - I suppose an espresso blend, for example, might go a little longer before blonding then the Brazil SO.

Richard wrote:I virtually always do a straighforward pull without Fellini or voodoo, doses in a 14-15g range in an Elektra basket, and my shots are right at 30g and sometimes a bit over.

...and sometimes a bit under? But I do agree that the output of a single Cremina pull is consistent and close enough to a full shot that one need not do any more. However, the improvements in taste with a Fellini preinfusion start have made me a believer in the method.

The answer is that you adjust for the flavor you want. I doubt a 15 second pull would be any good. That said, a lever can pull great shots in longer than 30s because of the declining temperature profile.

If I wanted a 1:1 I would grind finer and aim for a nominal 25-30s but I wouldn't worry if it were longer.

But why do you ask?

peacecup wrote:I suppose even with a commercial lever I would want to use active preinfusion via a Fellini pull. With the Strega one can use the pump.

Slightly OT, but the idea of "active preinfusion" got me curious. I don't care for the extra volume the Fellini move provides, but it seems like pretty much any spring lever group (well any lever group) can give you variable pressure preinfusion without extra volume. If you let the group fill with water then ease the lever up until the spring pressure begins to apply, then hold it there it should create a higher preinfusion pressure with a slightly decreasing profile as the puck saturates. It's not the more constant(?) preinfusion pressure profile a strega+dimmer-mod would provide, but effective. I've enjoyed the flavor change and lovely pours on the L1 if I ease the lever up until I see drops on the bottom of the basket and hold it there a few seconds. (I've tried it the past 4-5 doubles I've pulled.)

Thanks for the tip - one more tasty variable to play with!

just pulled a shot on the gaggia orione and measured everything:

coffee grounds before brewing: 18.5 gr

pre-infusion: 6 seconds
extraction: 35 seconds

shot weight: 39 gr
runoff after extraction: 11 gr
puck weight: 34.6 gr
theoretically retained water in puck: 16.1 gr (the coffee grounds have a weight loss [TDS, etc.} how much, i don't know])

total weight/volume of water: 66 gr/ml
that equals approximately the displacement with the following parameters:
piston diameter: 54 mm
maximum stroke: 29 mm

Interesting discussion. I was in a local roaster last week (49th Parallel) and a sales guy there was going on about how important it is to hit your "target mass" with a 28 second timed shot. But when i asked him about ratios to actually set a target mass (wet weight in the cup) he said there wasnt one. I dont use scales every day, so i went home to weigh my doses and shots and found about a 100% ratio in 30 seconds. I adjusted the grind coarser to get 17:32, close to a 50% ratio. I thought it tasted terrible. But, im wondering now of it makes a difference whether the machine is pump or lever. Im using a commercial Cimbali lever, but i find a much longer, slower pour to taste better (like 45 seconds to get the same 32 gram wet mass)

the 28 sec rule applies to pump machines, not lever machines! 28 sec is rather the lower limit.

I have been wondering about these issues myself. I think in general a 30 second pour for a standard shot works about right on most levers- but as others noted longer pours can also be good on a lever due tot he declining water temperature.

Does anyone know what the actual capacity of the chamber is in the average commercial lever? Is it 60ml or 30ml? I would have thought 30ml.

@sorrentinacoffee: look at my second previous post, displacement of a commercial lever is around 60-70 ml.

My CMA lever has a 2" diameter (1" radius) bore with a 1" stroke, giving us an easy-to-calculate pi cubic inches, which equates to about 51.5 ml.

This does not include the headspace over the grinds, or the amount that will soak into the coffee in the basket.