So far, I've always been making double shots on my Andreja Premium since I bought it two years ago, having read on several sights that it's much easier and makes better tasting espresso than using the single filter. Nevertheless, I always felt there was a lot lacking compared to the espresso I get in my favorite espresso bar. I just couldn't get the concentration or the mouthfeel that they make there. So I tried changing all possible factors (beans, grind, flushing methods etc.), but nothing helped.


Then I bought Erics device to measure the temperature, and I found that no matter the flushing method I used, the temperature would always drop at least 5-6 degrees during the extraction of a 17-18 gram double. Basic espresso science states that the temperature should be as stable as possible during extraction, so it seemed that the temperature drop was causing the poor tasting espresso. But what caused the drop in temperature? I figured it might have something to do with the amount of coffee used, so I began down-dosing to around 14-15 grams. There was still a temperature drop, but not as significant as before - I could now brew a double espresso that would only drop about 4 degrees, and the result was a clear improvement. So if the lower dose caused a more stable temperature, why not try the single basket?

So I now dosed 9 grams of coffee in the single filter, flushed the machine to around 204 degrees, made the shot right away and the temperature stabilized around 200 degrees during the whole shot! Had I hit the magic spot? You bet. The homeroast (50% pulped natural Brazil and 50% WP costa rican) just came to a whole other level. Much thicker, much more concentrated flavour, not bitterness and just a hint of sourness.

Conclusion: Temperature stability is the key to great espresso.

Now, the espresso that came out was definitely ristretto-style. The funny thing is that if I want to make a more normal faster running single-espresso by grinding a bit coarser, the temperature also drops. It's as if the machine has a magic spot, where the resistance of the puck makes the temperature completely stable, and in this case I just found the magic spot.

Has anyone else had the same experience with their E61-machines? And must one purchase a GS3 to be able to make a high quality double shot?

- Michael

Singles definitely exhibit a different flavor profile. Some coffees can be challenging to pull as singles.
Quickmill machines have the OPV is on the HX outlet rather than inlet, giving a different shot profile

Group temperature [w Eric's adapter on Vibiemme Domobar Super HX]


Scace puck temperature


As you can see, group tends to vary more than puck.
from Scale, HX Temperature Stability and a bit o' PID

klino wrote:Conclusion: Temperature stability is the key to great espresso.

Nope. Great coffee and grinder are key. Dose and temperature are adjusted to expose the potential of the coffee and grinder

klino wrote:And must one purchase a GS3 to be able to make a high quality double shot?

Nope. Bad coffee ground on a crappy grinder brewed on a GS3 yields dreck indistinguishable from an Andreja

Funny must be an european thing,
I NEVER make double ( unless I'm making it for more then 2-3 people) I always make singles

klino wrote:Basic espresso science states that the temperature should be as stable as possible during extraction, so it seemed that the temperature drop was causing the poor tasting espresso.

Definitely temperature stability seems to be in vogue, but I've also heard of 'temperature profiling' as another wave of espresso experimentation.

On another tack, with a lever machine doesn't the extraction ratio climb because of the lower dose, single basket compared to double?

Then I bought Erics device to measure the temperature, and I found that no matter the flushing method I used, the temperature would always drop at least 5-6 degrees during the extraction of a 17-18 gram double.

Firstly, thank you for the purchase.

The Quickmill Andreja and Anita are unique in the home espresso machine market to the extent that the installed OPV is DOWNSTREAM of the heat exchanger (hx). This is intended as a design feature and not a deficiency. The entire output of the Ulka pump (~ 4.33 ml/sec @ 9.0 bar) flows through the hx but only X ml/sec ends up in the cup. Contrast this with an Isomac, Vibiemme, or Giotto, et al where the X that ends up in the cup is the same X that flowed through their hx. Even though the Quickmill machines exhibit a declining temperature profile at the grouphead, the temperature of the water presented to the coffee is pretty darn flat. The reason for this is that the remaining mass of the grouphead in the flowpath downstream of the temperature measuring device does an amazing tempering of the temperatures. HOWEVER, for a "ristretto-ish" double shot on a QM vibe machine, you will see a more rapid decline in temps - its inherent in the beast.

I just couldn't get the concentration or the mouthfeel that they make there.

Even though you didn't say it, I assume you tried to duplicate their results with the same bean, the same dose, the same basket, and the same shot amount. This should at least have gotten you pretty close. And, if it didn't, a field trip to Denmark may very well be in order.

erics wrote:the installed OPV is DOWNSTREAM of the heat exchanger (hx). This is intended as a design feature and not a deficiency.

I get that they did it on purpose, but I don't get why. Do you have any insight into this design decision -- especially since other E61 manufacturers have gone the other way?

The results of this "feature" are:
- Declining temperature brew water delivery
- Unstable water reservoir temperature due to hot water exiting the OPV (Yes, most reservoir machines transmit ambient heat to the reservoir, but this is a more pronounced effect)

Yes, the heavy group head dampens temperature fluctuations from the HX feed, but that's not enough to convince me that a downstream OPV has any advantages. Any theories, Eric?

portamento wrote:Any theories, Eric?

Yea. That being that I'm not making any field trips to Denmark unless I visit the Nordic Barista Championship - http://www.nordicbaristacup.com/

I have no insights into this design other than it allows a duplicate installation on Vetrano where the valve performs the function of a thermal OPV. This saves some $ to the extent that a completely outfitted boiler could be applied throughout the line.

Note that the current line of Quickmill machines have the OPV positioned on the "cold" side.

erics wrote:Note that the current line of Quickmill machines have the OPV positioned on the "cold" side.

Including the Andreja Premium? So the latest AP has different thermal characteristics than the previous model?

Yes to both of your questions. However, 9 lbs of grouphead brass have always performed a nice job of tempering.

@Michael
Do you use the stock single basket that came with the AP, and do you tamp with your 58mm tamper?

Thanks
Pascal