Serving People Serving Coffee Since 2005
Issue link: http://baristamagazine.epubxp.com/i/659497
Above: A Modbar espresso module. Top right: The outer bean color can be mislading when examining a coffee's development. Below: A curved tamper and a fl at PUSH tamper. Adding coffee to a hopper can decrease flow rate because of the added weight on the burrs. Coffee freshness: The fresher the coffee, the more it will off-gas CO 2 , increasing the flow rate. Adding fresh coffee to a hopper with older coffee will eventually result in a sudden change in flow rate. Burrs heating: The more frequently burrs are used, the more they heat up. The coffee beans absorb most of this energy, causing fragments to change shape with increased heat. This causes flow rate inconsistencies when moving from low to heavy use, or vice versa. Retention: When the grinder is stopped, not all of the ground coffee exits the chamber between the burrs and your portafilter. The amount of grounds that are left in the grinder is called retention. Mixing fresh grounds with stale grounds will impact flow rate; removing the old coffee by purging will increase extraction uniformity. Adjustment lag: When making grind-size adjustment, you will need to dispense all retained grounds and bring fresh coffee through the burrs to begin operating at your new grind size. The amount purged is typically a full dose, but for grinders with high retention, it may take three or more doses to ensure you are operating on the new grind size. Clumping and inconsistencies: If you're seeing clumps in your portafilter, it's likely a sign that you need to clean your grinder. It may also be a sign of the age of your burrs, as clumping can increase with more fines. Dose Coffee weight: This is where most issues with quality begin. An unknown coffee mass will affect extraction and flow rate. Dosing an inconsistent amount will affect how slow or fast a shot will pull, which can cause a barista to misdiagnose a problem as a grind- setting issue. Quality begins with a consistent, weighed dose. Variance: Even great scales will display natural variances. 98 barista magazine