I've just started deploying the technique of weighing both the dose and the extraction, aiming nominally for the extraction to be double the dose, as a guideline for a "standard" (IOW not ristretto or lungo), double.

Anyhow, why talk of imprecision? Allow me to elaborate. I try for a dose weight of 14g. Thus I try for an extraction of 28g. But I grind from my Vario in real time, straight into the basket, with the basket sitting on the scales. Sometimes, (as in most of the time), I overshoot a wee bit and end up with say, 14.5g.

So the question:
If I end up with a 14.5 or 15g dose, I simply adjust my extraction weight up to 29 or 30g. I am operating under the assumption that the 1g variance in possible dose weights, paired with my compensatory heavier extraction, is NOT enough cause a "sink" shot or REQUIRE a change in grind.

Is there a problem with this technique?

-Peter

I think you are isolating two factors from the remaining variables. .5 grams in dose doesn't sound like a lot, but it is enough to possibly necessitate a change in grind setting. If you are serious about weighing the dose, then a scale that can weigh and display in increments of 0.1 grams is recommended. IMO, .5 grams of dose when you are trying to get all your stars aligned is a pretty wide range, particularly if the scale weighs by .5 grams. The range at 14.00 grams would be 13.75 to 14.24 or 0.49 grams.

I find that, especially with SO coffees, and especially with big-bottom baskets, a half-gram change in dosing results in a consistent change in flavor. Personally, if you're weighing, shooting for 0.1 g repeatability is worth the effort, even if it means that you're tossing half a gram of coffee on each basket, especially when you are pulling an expensive coffee. Cheaper to "waste" a half a gram on each basket than to "sink" 15-20 grams once a bag.

Pulling the shot slightly longer should give you about the same brew ratio. But that doesn't mean you'll get the same extraction, and therefore taste.

Coffee extraction doesn't always (ever?) work in a strictly linear way. I think it depends on a host of factors, including the coffee, roast level, dose, temperature and where you are in the extraction curve. For example, even slightly more contact time at a low dose (i.e., thin puck) might burn the coffee if the temperature is high enough. In contrast, a higher dose (thicker puck) would probably be more forgiving of a .5g error.

Rather that try to predict the unpredictable, why not pull a couple of shots and see if you can taste the difference?

Pull one shot at 14g to produce 28g of beverage. Pull a second shot at 14.5g to produce 29g of beverage (use a spoon to adjust the amount of coffee to the exact target weight.)

If you can't taste any difference between the shots, then it would seem that .5g difference in the dose doesn't make a significant difference to you (though it could be a function of shot-to-shot variations on your system.) If you can taste the difference, then I suggest you run the Vario to dose slightly more than 14g and use a spoon to remove excess coffee until you have 14g.

You should repeat this test with different coffees because, as was pointed out, dose sensitivity can vary from one coffee to another. Also, the answer may change depending on dose size. As suggested above, a .5g error is more significant for a 14g dose than a 22g dose. And, of course, the basket geometery can make a difference, too.

On my system, and with my taste buds, a difference of +.5g for a 14g dose is just on the edge of what I can detect. I usually can't detect a difference of .1g, .2g or even .3g. But at .5g the flow rate begins to change, and I start to taste some differences.

But if the grind remains the same, he adds a gram, and then waits until he gets 2 grams more output his shot time is going to be significantly longer, possibly pushing it into overheated, overextracted espresso depending on the type of machine?

Not saying the relationship between weight of extraction and duration of extraction is linear, but at least in the case of a conventional double, the desirable duration in seconds seems not far off from the target weight of extraction, in grams. A convenient coincidence?

-Peter

the_trystero wrote:But if the grind remains the same, he adds a gram, and then waits until he gets 2 grams more output his shot time is going to be significantly longer, possibly pushing it into overheated, overextracted espresso depending on the type of machine?

I tried to imply as much in my post, but probably wasn't clear.

Yes, at the same grind setting, adding more coffee will slow the flow rate and make the shot time longer. It'll take even more time to run the shot longer to get more beverage weight. All that added contact time could overheat and/or overextract the shot.

The lower the dose and the thinner the puck (wider basket hole area), the greater the chance of that happening. Again, the difference in dose is more significant at lower doses.

pcrussell50 wrote:Not saying the relationship between weight of extraction and duration of extraction is linear, but at least in the case of a conventional double, the desirable duration in seconds seems not far off from the target weight of extraction, in grams. A convenient coincidence?

Yep. Total coincidence. If you live in the non-metric world, the two numbers are far apart.

What non-metric world?

Great advice on the shot testing, by the way.