Everything is working great and I can say that the first shot (double) comes out at the perfect stream, honey tiger stripped and tastes great and I think I have arrived.

However

For no reason I can understand, I do everything exactly the same for the second shot (a double) and the flow is definitely slowed down.

Same Pressure Tamp (30lb Espro type tamper)
Same Amount (measured by a timer release)
Same Everything

I even wipe and clean the E61 Grouphead dry and wash out the Portafilter and dry it as well before pulling the second shot. The only difference might be a cooler portafilter for the second pull, by the time you have emptied and done everything, but not that much.

Any ideas Anyone ?? Thanks

Machine is a Vibiemme Domobar Super so theres plenty of pressure

Unless you run the timer for a second or two before the first shot, stale coffee [ < 15 minutes to stale ] makes up a significant portion of the shot.

misterdoggy wrote:....Same Everything

Probably not. If everything really was the same then we wouldn't be having this discussion....

For example, how long has the machine been on before the first shot, and how long is it until the second shot is pulled? This could affect brew temperature. How long do you flush before pulling the first shot? Before the second shot? How long do you wait after the flush before pulling the shot? Those variables alone could affect the performance of the machine. Do you have Eric's thermometer option installed?

The "same amount" of coffee cannot be accurately judged by the amount of time that the grinder runs- only the weight of the dose can do that accurately.

...and what cafeIKE said.

......and more.

Stale coffee grinds flow faster, not slower.

misterdoggy wrote:Same Amount (measured by a timer release)
Same Everything

I'd bet your dose is off. Timers are not that accurate. Get a 0.1g scale and weigh the doses.

Regardless, don't expect perfectly reproducible pours, unless you thrive on disappointment. In espresso, something is always different.

Well

I flush the E61 for a few seconds

then

I grind as need. Meaning I grind only the amount for the 1st shot and then pull.

Wipe dry both E61 grouphead and Portafilter and grind for the 2nd shot

Then I don't do the flush for the second one as its fairly quick (few minutes maybe) to the second
pull

Maybe I should flush before the second shot ?

misterdoggy wrote:Well ... I flush the E61 for a few seconds

I HIGHLY recommend Eric's adapter and digital thermometer. The consistency it supplies in regards to temperature makes a huge difference.

I'll second the recommendation for the EricS grouphead thermemeter.

I've said it before but I think this single modification takes the art out of flushing and turns it into a measurable and reproducible science.

I flushed before the 1st pull

then after it was finished, I did everything the same and

flushed before the 2nd pull

and they were the SAME

I had always thought that making the 1st cup was like flushing, but it is not

Anyhow looks like this is the solution