# Intermittent choked shots



## newtwit (Jul 13, 2015)

Hopefully I have posted in the correct forum, and I apologise in advance if a search should have worked, but I am struggling to come up with 'search' keywords for this.

There is an an intermittent issue with my setup which I just can't identify the source. Every 5-6 shots I pull, I get a choked shot, and after that it's fine again without changing anything. My process is as follows;

- 4oz cooling flush

- 18g in basket (every shot measured to 0.1g)

- 30 sec

- 32g liquid in cup (every shot measured)

I can get this within a few grams of liquid every time, with no grinder adjustment other than when starting a series of shots. The choked shot runs at about 4g for 30 sec after which the next shot runs at the usual 32g for 30 sec with no adjustment or change. My tamping is reasonably consistent I think, though I've not pulled out the bathroom scales in a while. I also rinse and dry the basket after every shot.

Equipment:

- Nuova Simonelli Oscar I

- Eureka Mignon

- Cast Iron coffee beans, though I find the problem occurs with any beans, and within the same bag/batch.

Hopefully someone with more experience can give me some pointers of what to try, as I just can't think of anything!


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## JayMac (Mar 28, 2015)

Is there any pattern timing wise?

I'm wondering if you could have an influence around the burrs in the Mignon heating up and cooling back off? Doesn't quite sound right but it's a variable a bit hard to control (other than making coffee less frequently) and in my experience Burr heating can slow shots and they return to normal when cooled down for a few minutes.


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## MWJB (Feb 28, 2012)

Isn't it a bit odd all the shots run for 30s? It's normal to have a little variation in shot time.

Are you grinding straight into the PF? If so, try grinding into a pot/cup, shake then transfer to PF, tap to level then tamp.


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## DavecUK (Aug 6, 2013)

I think you must be grinding really fine... what's the brew pressure of the machine against a blind filter. The shots are so short?

I think it might be channelling and then sometimes choking, especially when you do too or three shots in a row.


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## JayMac (Mar 28, 2015)

Regarding 30s, isn't newtwit just saying how much coffee s/he gets in 30s, meaning 4g (almost clogged) vs 32g (done, basically)?


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## MildredM (Feb 13, 2017)

Welcome (and love the name, by the way)









My first thought was your grinder having a hissy-fit every few shots, maybe. Or maybe it is a very fine grind that just occasionally you tamp slightly more forcefully. But it still seems strange . . .

It's an odd one alright.


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## MWJB (Feb 28, 2012)

JayMac said:


> Regarding 30s, isn't newtwit just saying how much coffee s/he gets in 30s, meaning 4g (almost clogged) vs 32g (done, basically)?


If you're getting varying weights, or even the same weight each time, the time will vary. If shots are killed at 30s the weighs will vary. It's not clear from the post whether shots are killed aiming for target weight, or a target time.


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## newtwit (Jul 13, 2015)

JayMac, thank you, that is definitely not something I'd thought of. I can't recall a pattern, but I will take note of whether it is due to a lot of shots. I usually run two shots at a time, and then a pause, but if I am adjusting the grind I would run more...


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## newtwit (Jul 13, 2015)

MWJB said:


> Isn't it a bit odd all the shots run for 30s? It's normal to have a little variation in shot time.
> 
> Are you grinding straight into the PF? If so, try grinding into a pot/cup, shake then transfer to PF, tap to level then tamp.


Hi MWJB, I am running all my shots to time (30 secs) and hopefully if all is right, I will get my desired 32g of liquid. If not, I adjust the grind.

I do grind directly into the PF, and there is some (loose) clumping so grinding into a cup first is definitely something I can try.


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## newtwit (Jul 13, 2015)

DavecUK said:


> I think you must be grinding really fine... what's the brew pressure of the machine against a blind filter. The shots are so short?
> 
> I think it might be channelling and then sometimes choking, especially when you do too or three shots in a row.


Hi DavecUK, the shots seem really consistent generally so I'm inclined to think it's not channelling, particularly as the taste is pretty good with a solid crema when it's running well. I don't have a way to measure pressure (yet) but the OPV doesn't seem to open under normal running...


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## newtwit (Jul 13, 2015)

MWJB said:


> If you're getting varying weights, or even the same weight each time, the time will vary. If shots are killed at 30s the weighs will vary. It's not clear from the post whether shots are killed aiming for target weight, or a target time.


Sorry, I should have made that clear in my post. I run the shot for 30 sec and then kill it, so running for target time, and using the grind to get the desired weight.


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## newtwit (Jul 13, 2015)

MildredM said:


> Welcome (and love the name, by the way)
> 
> 
> 
> ...


Afraid the name was a result of a total lack of inspiration







I should really get out the scales, but the fact I get a fairly consistent 4-5 out of six makes me wonder!


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## MWJB (Feb 28, 2012)

newtwit said:


> Sorry, I should have made that clear in my post. I run the shot for 30 sec and then kill it, so running for target time, and using the grind to get the desired weight.


That's the wrong way around. The intermittency probably has an additional cause, but killing by time & constantly changing grind will lead to inconsistent shots. Time has less of an influence on extraction than weight.


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## JayMac (Mar 28, 2015)

Hi Newtwit,

i thought your explanation of how you measure (constant time vs constant output) was what you meant.

i think you will find he standard advice is always pull x grams. 32, 36, whatever your recipe is, and aim for it taking roughly that same time, say 25-35s. At least if it is way too slow or fast you can still drink it that way. Not to say your method isn't decent science too though. But switching to constant volume/ weight would make your measurements more consistent with most recipes. Good luck!


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## JayMac (Mar 28, 2015)

I was so beaten to the punchline. Clearly I need to be more brief.


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## newtwit (Jul 13, 2015)

MWJB said:


> That's the wrong way around. The intermittency probably has an additional cause, but killing by time & constantly changing grind will lead to inconsistent shots. Time has less of an influence on extraction than weight.


Thank you, I had not realised the impact of weight was greater than time, I may need to rethink!


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## newtwit (Jul 13, 2015)

JayMac said:


> Hi Newtwit,
> 
> i thought your explanation of how you measure (constant time vs constant output) was what you meant.
> 
> i think you will find he standard advice is always pull x grams. 32, 36, whatever your recipe is, and aim for it taking roughly that same time, say 25-35s. At least if it is way too slow or fast you can still drink it that way. Not to say your method isn't decent science too though. But switching to constant volume/ weight would make your measurements more consistent with most recipes. Good luck!


Might make my life a little easier if I switch over to constant weight by the sound of it, thank you.


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## newtwit (Jul 13, 2015)

The only left of field idea I had is that when I recently replaced the boiler (long story, and took me a very long time!) and found that lime scale was disturbed and made it's way into the solenoid valve and blocked it. This had the same effect of sounding like the machine had choked.

The reason I don't think this is the issue, is that I had to remove and clean the solenoid to fix, and this just seems to be intermittent.


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## DavecUK (Aug 6, 2013)

newtwit said:


> Hi DavecUK, the shots seem really consistent generally so I'm inclined to think it's not channelling, particularly as the taste is pretty good with a solid crema when it's running well. I don't have a way to measure pressure (yet) but the OPV doesn't seem to open under normal running...


It should do!


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## 9719 (Mar 29, 2015)

Below is a link to what should be compulsory reading for all members, new and old, it's the bees doodahs on how to measure your dose. It explains everything you need to know on the subject and is well worth taking the time to read a couple of times and digest it.

https://coffeeforums.co.uk/showthread.php?t=22879


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## newtwit (Jul 13, 2015)

********** said:


> Below is a link to what should be compulsory reading for all members, new and old, it's the bees doodahs on how to measure your dose. It explains everything you need to know on the subject and is well worth taking the time to read a couple of times and digest it.
> 
> https://coffeeforums.co.uk/showthread.php?t=22879


Thanks **********, it's a great read! As pointed out earlier, the main deviance from this is that I have been using time as my constant rather than weight.

Even so, given this change in method and applied to my current issue, I would have a shot every now and then that ran for over a minute to get 32g - and it really can be a minute as I've tried it!


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## MWJB (Feb 28, 2012)

newtwit said:


> Thanks **********, it's a great read! As pointed out earlier, the main deviance from this is that I have been using time as my constant rather than weight.
> 
> Even so, given this change in method and applied to my current issue, I would have a shot every now and then that ran for over a minute to get 32g - and it really can be a minute as I've tried it!


You're pulling very short shots, whilst the difference between 30s & 60s is very large (at the same grind setting & ratio) I'd be more inclined to drink the 60s shot.


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## newtwit (Jul 13, 2015)

DavecUK said:


> It should do!


Sorry, my lack of correct terminology again! I think I meant the pressure relief valve, which I understood on the Oscar would only open under 'dangerously high' pressure. I have an OPV kit for the Oscar, but have not installed it yet.


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## newtwit (Jul 13, 2015)

MWJB said:


> You're pulling very short shots, whilst the difference between 30s & 60s is very large (at the same grind setting & ratio) I'd be more inclined to drink the 60s shot.


Probably right, but I tend to bin it, as my litmus test (my wife) won't drink it...

It's not a big issue, just one that was irritating me enough to seek advice


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## newtwit (Jul 13, 2015)

Thanks everyone for your comments, I have a few things to try - burr temp, extracting to weight etc.

Does anyone think it would be work picking up a simple portafilter pressure guage? I could run 5-10 shots into it consecutively and see if I get a variation in pressure...

Of course I am now wondering if I need to try a different grinder


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## MWJB (Feb 28, 2012)

newtwit said:


> Thanks everyone for your comments, I have a few things to try - burr temp, extracting to weight etc.
> 
> Does anyone think it would be work picking up a simple portafilter pressure guage? I could run 5-10 shots into it consecutively and see if I get a variation in pressure...
> 
> Of course I am now wondering if I need to try a different grinder


Wait until you have revised your prep & method. If you start assuming everything is the cause (pressure, grinder) this thread will still be running in a year's time. Deal with the simple things that have the biggest impact first.


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## newtwit (Jul 13, 2015)

Right - prep & method revised, results as follows

Monday

32g - 30 sec

32g - 29 sec

32g - 41 sec

Tuesday

32g - 29 sec

32g - 31 sec

32g - 62 sec

Today

32g - 29 sec

32g - 32 sec

32g - 30 sec

32g - 33 sec

A bit more fluctuation in time than I like as I was aiming for 32 sec, but given the nature of the test, I made only very small grinder adjustments. Any thoughts/ideas on troubleshooting the highlighted timing?


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## MWJB (Feb 28, 2012)

newtwit said:


> Right - prep & method revised, results as follows...
> 
> ....A bit more fluctuation in time than I like as I was aiming for 32 sec, but given the nature of the test, I made only very small grinder adjustments. Any thoughts/ideas on troubleshooting the highlighted timing?


You haven't told us how they tasted in comparison, was there any common attribute or fault with the 41s shot?

How have you changed your prep?

I still don't get why you are aiming for 32s (or any specific time). I would be aiming for a tasty shot.

How much are you purging from the grinder between shots?


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## newtwit (Jul 13, 2015)

MWJB said:


> You haven't told us how they tasted in comparison, was there any common attribute or fault with the 41s shot?
> 
> How have you changed your prep?
> 
> I still don't get why you are aiming for 32s (or any specific time). I would be aiming for a tasty shot.


Thanks, the shots that run to 32 sec are tasty, the shots that run long are not. My question and the reason for the post, is trying to discover the cause of the intermittent long running shots.


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## MWJB (Feb 28, 2012)

newtwit said:


> Thanks, the shots that run to 32 sec are tasty, the shots that run long are not. My question and the reason for the post, is trying to discover the cause of the intermittent long running shots.


So, purging, how much?

What is your dosing (hopper, singe dose?) & puck prep regime (grind into PF, grind into cup shake & transfer to PF?)

All shots were pulled at the same grind setting?

The 41s shot is not outside normal parameters. It's only the one 61s shot that looks odd.


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## newtwit (Jul 13, 2015)

MWJB said:


> So, purging, how much?
> 
> What is your dosing (hopper, singe dose?) & puck prep regime (grind into PF, grind into cup shake & transfer to PF?)
> 
> ...


Thanks MWJB my process is as follows;


Remove basket, rinse and dry to clear any fines

Grind directly into basket (18g)

Gentle tap to level, and also smooth any loose clumping (this does occur with Mignon, but does not require much to shake up)

4oz cooling flush

Run shot until 32g liquid in cup <change to process according forum advice>
</change>


I adjusted the grinder after shot 7 as it was running a little short, hence the slightly longer shots after that point.

Given the relative consistency of the timings, I am minded to rule out my prep for this particular issue. I do wonder whether there is an issue with fines collecting in the grinder and being ejected from time to time as there is some inevitable retention in my grinder.


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## MWJB (Feb 28, 2012)

newtwit said:


> Thanks MWJB my process is as follows;
> 
> 
> Remove basket, rinse and dry to clear any fines
> ...


The lack of consistency in timings is why you started the thread.

Your last 3 shots have been consistent. It would be more telling to see if this continues.

Are you purging a few grams from the grinder between shots to ensure you are getting the current dose? Do you have the same weight of beans in the hopper for each shot?

I think you are overthinking this, re. fines etc.

Don't grind into the basket, grind into a cup/pot/similar, shake it, then transfer to PF.


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## newtwit (Jul 13, 2015)

MWJB said:


> The lack of consistency in timings is why you started the thread.
> 
> Your last 3 shots have been consistent. It would be more telling to see if this continues.
> 
> ...


Yes, absolutely, the reason I started it was the intermittent inconsistency of one shot in every 5 - 6, the other shots I am currently very pleased with.

I'm not sure of the relevance of weight of beans in hopper etc. as I weigh the basket. Thanks for all your suggestions to date, but I guess I will need to continue my process of elimination.

Best regards.


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## Kitkat (Jan 25, 2018)

I have a mignon and it can be very clumpy at a fine grind. I thought I was stirring enough to break up the clumps but I've recently changed my prep and after pouring from a jug into the portafilter (much stirring and shaking beforehand) there can still be clumps that I didn't reach. The tap that you describe may not be getting rid of all the clumps and you may be getting channelling which is slowing down things.


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