I have had my 870 for over a year now and have been pretty happy with it. In recent months I have noticed that the extraction pressure seems to go way up on the second shot that I pull after turning the machine on. I will turn on the machine as usual, run a blank single shot through to warm the parts, then grind somewhere around 18g for a double. The extraction will go just as intended, I will rinse out the portafilter, and repeat the process (minus the blank single shot run). On this second extraction, the pressure will go way up and the machine will act as if I changed my grind or dosage. For whatever reason, I am having to grind my first double differently than any subsequent shots.

Is this a fault with the machine? User error?

On an unrelated note, I have been playing with dose and grind recently because I haven't been quite able to get the same strong flavor in my lattes that I will taste at the coffee shop. Using their beans, my lattes just aren't near as flavorful as if I purchase one there. I have upped the dose as far as I can go but am still not getting quite the same results.

Thanks in advance.

I flush the machine between shots... to make sure that the shower screen is clean and that the holes in the PF are not clogged. Might want to try that before filling the basket...

Are you purging any coffee out of the grinder before the first shot?

So you are thinking that he is overdosing for the second shot from grounds that could be left over from the first shot?

I usually just make one shot and that is it... at least during the week.

If it is not due to overdosing... or due to lack of flush (cleaning basket and shower screen)... I doubt is thermal expansion related of the basket

I have several PFs, all with double baskets... I can test two back to back with the same basket and then one with another pf and basket.

But I have not had this issue during the weekend (when it is when I do several shots for me, wife, and father-in-law).

wachuko wrote:So you are thinking that he is overdosing for the second shot from grounds that could be left over from the first shot?

Or that if he is not purging, that he is using partially stale grounds (grounded when he used the machine previously) on his first shot, but I'm not knowledgeable enough to know if that would make any noticeable difference in extraction pressure.

That still does not explain why the OP has only been experiencing the issue in recent months and not since the beginning.


Nathan,

How are you measuring the amount of coffee going in?
How long does the machine have to be off before it goes back to proper extraction pressure?

Yes, the stale coffee is more than sufficient to change the first shot. Also, at least on mine, the dosing is not very consistent. I personally only ever recommend this machine as a latte machine.

It could be that he simply didn't notice it before if that is his first machine.

Does anyone know how much coffee is left behind in the grinder/chute mechanism? Another words, how much would have to be purged to ensure all previously ground stale coffee is gone?

escape wrote:Or that if he is not purging, that he is using partially stale grounds (grounded when he used the machine previously) on his first shot, but I'm not knowledgeable enough to know if that would make any noticeable difference in extraction pressure.

That still does not explain why the OP has only been experiencing the issue in recent months and not since the beginning.


Nathan,

How are you measuring the amount of coffee going in?
How long does the machine have to be off before it goes back to proper extraction pressure?

I actually don't keep any beans in the hopper. I like to change beans quite often so I keep it empty. I measure the dose in a shot glass type container that turns out to be almost the exact volume of 18g of beans. I also normally weigh the dose before they get ground.

HoldTheOnions wrote:Yes, the stale coffee is more than sufficient to change the first shot. Also, at least on mine, the dosing is not very consistent. I personally only ever recommend this machine as a latte machine.

It could be that he simply didn't notice it before if that is his first machine.

It is possible I never noticed, hard to say. But I do feel as if it has gotten worse recently. It's also possible that the beans I've been using in the past several months have exaggerated the problem as compared to before.

I am noticing the same thing, and mine is brand new.

I might have to start using a standalone grinder because it's really hard to achieve consistency using the built-in grinder.