Intro to Advanced Brewing
Budget espresso machines typically use pressurized baskets or portafilters that both artificially build pressure in the basket to increase contact time and aerate the coffee to give the appearance of crema. Non-pressurized baskets and portafilters such as you find on the Flair system, as well as all commercial espresso machines, require you to properly grind, dose, distribute and tamp in order to achieve the resistance needed to brew with 6 – 9 BAR pressure. Being off by even a little will yield disastrous results when you introduce pressure to the system.
For espresso, only use a quality burr grinder which creates more uniform grounds than a blade grinder can and allows you to accurately control your grind size. Your burr grinder must be able to grind not only fine enough for espresso, but also precise enough so that you have more of the right sized particles to extract. A grinder with alignment issues, burr wobble or dull burrs will yield a very wide spectrum of particle sizes. An uneven grind will cause your coffee grounds to both over and under extract, all at the same time, because the size of the particles determines the amount of surface area, and that dictates how short or long the contact time needs to be to properly extract the coffee (all else being equal). Additionally, a grinder with too few adjustment points will prevent you from targeting the optimum particle size. You will need 60 or more adjustment points to obtain a good result, the more the better and we highly recommend a grinder that is “step-less” or else has hundreds of settings.
As coffee ages, it loses the CO2 generated in the roast process that is chiefly responsible for crema. Always try to extract coffee that has been roasted within days or weeks, rather than months for the best flavors and most crema. When you grind your beans you are fracturing the cell walls that hold in CO2 and other volatiles from the roast process. For best results, you should only grind your freshly roasted coffee just before it will be extracted. Every minute counts as you set the clock ticking on aroma and CO2 loss, and the onset of oxidation.
Brewing with a Pressure Gauge
Brewing time should typically be between 30-45 seconds at 6-9 BAR pressure, sustained. Light roasts might require even more time for proper extraction. Everything starts with the grind and dose, which creates the resistance to achieve desired pressure and brewing time. Use the Brew Chart below to adjust your grind and dose appropriately so that you can target ideal pressure and time.
The PRO uses a non-spouted portafilter, a so-called “bottomless” or “naked” portafilter. Removing the spout(s) provides an unobstructed view of the filter screen where the extraction happens. With the help of a small compact mirror, ideally with 3-5x magnification, you can easily observe the extraction as it occurs. This is vital information for determining the evenness of extraction across the entire coffee bed. A spouted portafilter hides this.
If you observe regions that are significantly lighter or darker than the average, you have areas of over or under extraction relative to the whole. This suggests that there may have been issues with your distribution or tamping for that given shot, and that brew water has flowed more easily through some parts of the coffee bed than others due to channels opening up under pressure.
When you lay bare the bottom of the basket in this way, spritzes and spurts can develop and coffee can spray objects below. Just as when you place your thumb over the opening of a garden hose to create a “jet effect” and propel the same flow further to reach parts of your garden you’d otherwise not reach with the water pressure at your home, the openings in your filter basket can clog and create the same effect. Coffee beans are comprised of both soluble and insoluble solids. Sometimes the insoluble materials lodge themselves inside the perfectly circular holes and create the same partial occlusion that you do with your thumb. Sometimes channeling occurs and allows water to flow faster in one region of the coffee bed than another and this “jet” of water will exit the filter screen at a higher velocity than the rest of the streams. There’s little we can do about partial occlusion, but channeling can be combatted with good distribution techniques and pre-infusion.
TIP: if a jet of coffee occurs, a subtle and momentary decrease in pressure is sometimes enough to either dislodge the material or collapse a formed channel.
Pre-infusion is the act of wetting your coffee grounds with low pressure for a short period of time, usually 5 – 20 seconds, before commencing extraction, and consequently, applying higher pressure. The goal is to soak the entire puck, evenly, without kicking-off extraction. By doing so, you can achieve higher extraction rates and minimize the occurrences of channels forming in the coffee bed when higher pressure is applied. The PRO is equipped with a bottomless portafilter. Once coffee begins to drop into your cup, extraction has begun. By monitoring the filter basket from below, you can accurately control the low-pressure pre-infusion and prevent extraction from occurring by backing off or holding pressure when you see the first drops beginning to push through the filter. To introduce pre-infusion into your brew, slowly pulling lever down until 1-2 BAR is achieved, and then hold the lever still for the desired period of time has elapsed. Once you have reached the desired dwell time, move forward with extraction as normal.
It’s important that you do not release pressure in between pre-infusion and extraction phases e.g. apply low-pressure, hold, apply high-pressure and complete the pull. For the o-rings installed inside the cylinder to engage and seal against the portafilter, the commencement of the pull must be marked with a constant and firm force on the lever. Should the force applied to the lever waver or diminish, the cylinder may rise up in an attempt to release pressure and this will result in some leaking. NEVER PUMP THE HANDLE. If you do not wish to include a pre-infusion in your brew, we recommend a slow ramp up from “0” to your desired brew pressure. Always continue in the direction of the pull once you have started.
You can use the gauge to implement pressure profiles that mimic other machines - from other lever-based machines, to high-end modern pumps with customizable pressure profiling capabilities. As you pull the shot, you can ‘draw’ the pressure accurately against the time axis with the help of a timing device such as your phone, watch or a coffee specific scale that includes a timer. Two examples of possible profiles to try are shown below. One is similar to a conventional straight 9 BAR pump machine while the other a lever. Using a timing device, attempt to hit the pressure changes at the appropriate time. Also notice that in both of these examples, there is a slow ramp up of pressure before peaking at 9 BAR. It is believed that the act of ramping slowly as opposed to immediately hitting peak pressure, higher yields can be achieved. You will discover that you can grind finer while achieving the same brew ratios obtained from going straight to peak pressure using a coarser grind. Where this ability to grind finer really comes in handy is achieving a higher extraction of lighter roast which typically are a challenge to find the right levels of sweetness, acidity and body one is hoping for in an espresso.
CAUTION: If you find that you have ground too finely and there is little to no flow occurring into your cup with a pressure as high as 10 BAR, you’ll need to start again with a coarser grind and/or lower dose. At this point, you have built up pressure within the chamber that will need to be released before you remove the brew head from the base. Using your free hand, hold the brew head down firmly while you raise the lever fully. Next, while still holding down the cylinder, lift up on the stem of the piston (the part the gauge attaches to). This will release the pressure in the system and make it safe to remove the brew head from the base. Skipping this step may allow the cylinder to “pop-up” and off the portafilter, releasing the brew water within.