# Strange fast->slow pour



## bronc (Dec 10, 2012)

I'm using a Gaggia Classic, Iberital MC2 and Rave Coffee's Signature Blend. The problem is that the shot starts pouring perfectly and then midway it just slows down massively and starts dripping. This was happening previously using my Tiamo and using the Iberital. Why can this be happening? My last shot started pouring quite fast in the beginning, then went to dripping and overall I got 23-24ml in 27sec but I don't think this is the way it should be extracted. I tamp once and then just twist and remove the tamper using my Motta tamper. Maybe this is some kind of channeling? I don't have a naked portafilter so I can't tell.


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## The Systemic Kid (Nov 23, 2012)

It's not channelling Bronc. If it was, you would not get the slowing down during extraction. Has the problem coincided with you beginning to use a new coffee? If so, can you go back to when you last got a good extraction in the 27 secs and repeat that set up. If you can't, try the following. Clean you machine by removing the shower curtain and backflush. If that doesn't work then try this - assume you are weighing your doses - if not, would be a good idea to do so to ensure repeatability. Back off you grind, dose and tamp quite lightly - just ensuring you have a level puck that has a smooth surface. If that improves the shot extraction but doesn't totally sort it, back off the grind and try again. See how that goes.


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## bronc (Dec 10, 2012)

It all started when I began using my home roasted Brazil Daterra Bourbon beans and I thought that the problem was there. Then I got my Rave Coffee beans and things haven't changed. However, I can say that it coincides with this problem:



\ said:


> So I finally got an Iberital MC2 (thanks to Sam__G) and some fresh beans from Rave Coffee and got to dialing them in. Still haven't achieved a good shot but I'm getting there. However, I did notice a problem with my Gaggia. After making a rather slow shot (30sec, 17gr) I tried to flush some water through the grouphead to clean it from the coffee grounds. When I pressed the brew switch the pump was really quiet and there was close to no water coming out of the grouphead. I turned off the machine for 1-2 minute and tried again. This time everything was fine. Is the pump dying or can it be something else like..? The machine hasn't been backflushed because I don't have any puly caff/blank basket. I will descale it today to see if that will help. Thanks!!
> 
> P.S. I have also noticed that often when I start my shot it begins by pouring perfectly and then starts to barely drip. Can these be related?


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## The Systemic Kid (Nov 23, 2012)

Different beans and especially degree of roast can throw your grind settings out quite a lot. As suggested, back off your grind and keep other variables unchanged - especially dose weight which should be around 16grms IMO for the Classic. Don't tamp excessively and *definitely avoid *applying any pressure when you you twist at the end of you tamp. This way, you can establish of it is the beans that are causing the problem. Hopefully, you will get a weak, i.e. fast extraction with no fluctuations during extraction and can then adjust your grind to get into the sweet zone. Hope this gets you going again.


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## bronc (Dec 10, 2012)

Thanks! I'm dosing 15gr and weighing both the input and output every time in order to achieve consistency. I will try to back off the grind a bit and will be careful with the tamping. I just backflushed it and a lot of gunk came out so this might be helpful as well.


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## garydyke1 (Mar 9, 2011)

Wild stab in the dark - Could be the grinder.

If the particle size range is too big (ie lots of comparitive rocks and fines) you could be having 'fine migration' at which point the fines cause the shot to choke/stall. Shame you havent got a brew pressure gauge to validate the theory


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## The Systemic Kid (Nov 23, 2012)

bronc said:


> I just backflushed it and a lot of gunk came out so this might be helpful as well.


That sounds encouraging. It will certainly help the shot taste.


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## bronc (Dec 10, 2012)

garydyke1 said:


> Wild stab in the dark - Could be the grinder.
> 
> If the particle size range is too big (ie lots of comparitive rocks and fines) you could be having 'fine migration' at which point the fines cause the shot to choke/stall. Shame you havent got a brew pressure gauge to validate the theory


Well, I find it difficult to believe that it's the grinder because it happened with both the Tiamo and the Iberital. I have a few projects that I need to work on at the moment, but as soon as I have some spare time I'm going to make a brew gauge because I want to adjust the OPV.


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