Thursday, March 1, 2012

Eliminating the guesswork when flushing a E61 group.

With Eric S temperature Adaptor (or the Danish equivalent "Thebat18 Device") you are essentially eliminating the guesswork of how much to flush in order to achieve the correct brew temperature on an E61 group based espresso machine.

The two preferred methods of flushing E61 group using Eric S Temperature Adaptor are the so-called Flush-and-Wait (Rebound) and Flush-and-Go methods.

For the Flush-and-Wait method you flush the group well below the brew temp then pull the shot when the thermometer is a few degrees Celsius below the brew temperature. The few minutes after the flush will heat the water in the heat exchanger (HX) to over brew temperature. This super-heated water then cools back down to brew temp when it hits the group which is cooler than the desired brew temp. Therefore you should deduct 2 degrees Celsius from the thermometer reading to get the actual brew temp. 
When using the Flush-and-Wait/Rebound method on my Giotto Classic with a boiler pressure of 1.2 Bar I flush until the thermometer shows 86 degrees C, then wait a couple of minutes (time enough to grind, distribute and tamp) until the thermometer reads 92 degrees C and then brew. The temperature should land between 96-96.5 degrees throughout the shot meaning an actual brew temperature between 94-94.5 degrees C.

With the Flush-and-Go method, the group will be a few degrees Celsius hotter than the desired brew temp.  The HX water is cooler than the brew temp and heats back up as it hits the group. Therefore you should add 2 degrees Celsius to the thermometer reading to get the actual brew temp.
A generic example of using of the Flush-and-Go method on my Giotto would be to flush until the thermometer reads 95 degrees C, wait around 8-10 seconds until the thermometer reads 98 degrees C and brew immediately. The temperature should land between 92-92.5 degrees throughout the shot meaning an actual brew temperature between 94-94.5 degrees C.

The Flush-and-Wait method is simpler is because the group temperature is controlled via the flush and is consistent with every shot because you are over-cooling and waiting for the correct brew temp. 

With the Flush-and-Go method the idle group temperature will be different depending on the time between shots. The idle group temp determines the flush length and necessitates a chart to obtain consistent shot temps under any circumstance.







Using the chart which might seem a little cryptic at first, you will find your idle temperature on the left side of the chart (The thermometer reading at idle) and the desired brew temperature in the top of the chart. So to achieve a brew temperature at 93.5 degrees C at an idle temp of 98 degrees C, you should flush until the thermometer reads 95.5 degrees C. Please note that the above temp readings were made on an Izzo Alex HX machine and the final brew temp might be slightly different on your machine. On my Giotto I need to add an extra 1 degree Celsius to the Desired Brew Temperature numbers to get it right.

All credits for the above article goes to Mike Ripple in Michigan, US - a Home-Barista.com user (AKA Mike01)who made all the above temperature readings on his Izzo Alex.

2 comments:

Alex Stabile said...

I am following this flush and go method on my Giotto but how does this apply to the second shot if you pull it right after since the reading is already below the first time around?

Let's say my idle is 96.5 and I flush to 96.5. Now for the next shot, I start flushing but my idle is lower. Do I use the new idle in the chart or the original idle temp?

Thanks!

Sonne said...

Hi Alex. It's been a while but that's how I remember it, yes.