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Addressing Inconsistency

Consistency is the first challenge we need to overcome if we are going to serve great coffee to all of our customers.  We may be able to make the ‘God’ shot when we’ve got all the time in the world, but how do we maintain a consistent standard in the pressure of service?
The answer often comes down the process.

Low shot to shot consistency

Low shot to shot consistency can be caused by a number of issues, including: 

  • Variation in coffee dry dose (the amount of coffee in the basket).  If you have an electronic dosing grinder check that it is delivering a consistent dry dose into your porta-filter (be aware of any spillage when you’re dosing into the porta-filter, this will throw your dry dose out).  If you have a manual dosing grinder check your levelling off process is delivering a consistent dry dose every time. You can check if dry dose consistency is a problem by weighing your porta-filter after dosing a and observing the variation in weight between doses.  You should be looking for less than 0.5g difference between dry dose weights. Any more than this will be creating a considerable difference in resulting shot times (the lower the better)
  • Uneven distribution of coffee in the basket.  Check the distribution of the coffee being delivered to the basket by the grinder. You want the grinder to deliver the coffee as evenly into the basket as possible.  This may require moving the porta-filter around during dosing to even out the distribution. It is very hard to correct an uneven distribution once the coffee is in the basket, even with fancy distribution techniques and tools.
  • Crooked tamping.  Ensure coffee is being tamped straight up and down.  Tamping off true creates a sloped coffee bed which presents a weak point for the brew water to push through.  The resulting inconsistency in extraction will yield unpredictable shot times as well as inferior tasting coffee
  • Equipment.  Temperature/pressure variations, leaky group-head seals and incorrectly programmed volumetrics will throw shot times out.  If in doubt it might be time to get your equipment machine serviced

Low shot time accuracy

If shot to shot consistency is high but shot times are drifting out of the target band you need to improve shot time accuracy.  Issues that can affect shot time accuracy are:

  • The grinder not being adjusted often enough.  Adjust the grinder as soon as shot times trend away from the target time (but don’t get too eager, you need to see a trend, not just one rouge shot)
  • The grinder being adjusted in too large increments.  Make smaller grinder adjustments more frequently to get a feel for how adjustments are affecting shot times.  Keep adjusting towards the target shot time. If you wait until you need to make a large grinder adjustment, not only have you been serving inferior coffee but under/overshooting the adjustment becomes very likely
  • Bean variation.  Changes in bean condition will impact on shot times.  Make sure your stock rotation is enforcing beans are used from the oldest roast date to the newest.  Mixed up stock will wreak havoc on consistency, sending shot times all over the place when beans of differing roast date/condition go through the machine
  • Beans too fresh/too old.  Very fresh coffee can cause instabilities in shot times due to large amounts of CO2 being released during the extraction.  Conversely old coffee can require such a fine grind to achieve the shot time target that it’s very easy to jam the extraction completely leaving little margin for error.  Keep an eye on stock dates and adjust ordering to ensure your using beans of an appropriate age

Coffee is not an easy business, but a methodical approach can get us to consistent results.  If we are going to win our customers trust and their ongoing business we need to give them an experience they can rely on.

If you’re struggling with consistency in your coffee production, don’t give up, you can get there.  You need to systematically weed out the variations in your process and change one thing at a time.


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