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How to Calibrate Semi Automatic Espresso Machines

How to Calibrate Semi Automatic Espresso Machines
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Use this quick reference guide as a starting point to calibrate your semi automatic espresso machine out of the box. The guide should actually read "How to Calibrate an Espresso Grinder", hence the grinder in the picture.

Use this quick reference guide as a starting point to adjust and calibrate your semi automatic espresso machine out of the box. The guide should actually read "How to Calibrate an Espresso Grinder". As you know, the grinder is as important as the espresso machine, if not even more important.

Espresso brewing variables:

  1. Fresh clean water
  2. Fresh Beans
  3. Grind (fineness)
  4. Gram Through (weight)
  5. Tamping Pressure
  6. Water Dosing (Shot Size)
  7. Brew Pressure
  8. Brew Temperature
  9. Extraction Time
  10. Pre-Infusion

Water Quality:

98% of your coffee is water. A great tasting espresso starts with fresh clean water.

Another point to consider is the water hardness. The more minerals in the water, the better the aroma extraction. However, the espresso machine will scale up much faster and if not dealt with properly, by descaling frequently and on time, will destroy the machine in a very short time.

The following article will talk more about the effect of hard and soft water:

https://www.espressoplanet.com/espresso-coffee-machine/hard_water_equipment.html

Coffee Beans:

Nothing compares to brewing espresso from freshly roasted coffee beans. Try to find a local micro coffee roaster that can roast coffee to order or roasts on a weekly basis.

BTW: We have our own coffee blends, most of them roasted by-weekly. We also carry some great locally roasted coffees.

If you're wondering how many and what kind of flavours, or better aromas, are found in coffee, look at the Coffee Tasters Flavour Wheel by the SCAA (Specialty Coffee Association of America).

https://www.espressoplanet.com/SCAA-Unveils-a-Whole-New-Coffee-Taster-Flavor-Wheel.html

One of the most important steps in a great tasting cup of coffee is the blending and roast process. The Roast Master will determine the best roast profile to enhance tha flavours and aromas of the selected green beans and region.

Generally a darker roast (French or Italian) will taste bold, strong with full body while a lighter roast (City or Vienna) will taste acidic and bright.

How to Calibrate an Espresso Grinder:

When adjusting your grinder to a finer setting, do so only while the burrs are rotating (grinder running) otherwise you may damage the adjustment mechanism.

As you adjust the grinder finer, you'll see little balls forming (clumping) when you shake the portafilter sideways. This is a good starting point. If you go too fine, you end up with powder. That is too fine for most espresso machines, good for Turkish coffee though. Many grinders will clog up if you grind too fine.

A standard 58mm double portafilter basket will hold approximately 17-18 grams of ground coffee. Fill the basket to level. Use a straight edge, like a knife, to level off the ground coffee.

If you own a Baratza Grinder, you can find some grind setting recommendations (as a starting point) in the following article:

https://www.espressoplanet.com/baratza_grind_settings_how_to.html

Tamping:

Check if your espresso machine features pressurized portfilters or baskets. If it does, the grind settings and tamping won't be that important as this feature helps the extraction process.

The average tamping pressure should be around 30lbs. Practice this on a weigh scale and try to consistently tamp with the same pressure. The Espro 30lbs calibrated tamper helps with this step.

Try to tamp down straight or in level. If you tamp with a skewed arm or wrist, you will get channeling (uneven extraction).

Brewing Ratio for Espresso and other Coffee Beverages:

The brew ratio affects strength and taste of the coffee. It is expressed in ground coffee in grams per liquid coffee in grams. For example a typical double portafilter will hold approximately 18 grams of ground espresso and if we pull a 36ml (1.2oz.) shot we end up with a brew ratio of 50%, a typical espresso.

Brewing Ratio
(ground coffee in grams / liquid coffee in grams)
Drink Range Average
Ristretto 60% - 140% 100%
Espresso 40% - 60% 50%
Lungo 27% - 40% 33%
Cafe Crema
(Pressure Brewed Coffee)
12% - 27% 20%
Drip Coffee
(SCAA standard)
5% - 6% 5.5%

 

Brewing Pressure:

Many consumers are concern about how high the pump pressure capacity of an espresso machine is before they buy a machine. It is believed that a 18 bar pump will produce a better espresso then a 15 bar pump. It is very likely that the pressure on many machines is too high, making it very sensitive to the grind setting.

The ideal brewing pressure for an espresso is between 7 and 10 bars. Off course you need an espresso machine with a working pressure gauge. If the pressure is below, set your grind a bit finer or tamp a bit harder or add more coffee to the filter basket.

Read the next section about lowering the brewing pressure by adjusting the OPV (over pressure valve):

Extraction Time:

The contact time between hot water and ground coffee is referred to as Extraction Time. It is probably one of the most important brew variables, pending who you listen to. The ideal extraction time depends on the coffee bean, roast colour, gram through, desired taste profile and much more. Just browse the internet for "God Shot" to find millions of opinions on the ideal extraction time.

Generally, the darker the roast colour, the shorter the extraction time (15-25 seconds) and the lighter the roast colour, the longer the extraction time (20-30 seconds) should be. These recommended extraction times are for a double shot (14-18 grams) and a 1.5oz. to 2 oz. shot size.

If you find the shot is flowing too fast (short extraction time or shot size too large) adjust the grinder finer, tamp a bit harder or increase the dose (add more coffee to the filter basked).

As mentioned, many espresso machines have the pressure set too high. Most machines have an adjustable over pressure valve (OPV). If you find it very difficult to slow down the flow, try lowering the brew pressure by adjusting the OPV valve lower.

When you start seeing the crema turning white in colour (like 2 white dots) you can stop pulling the shot as all the oils (aroma) are extracted. A bottomless portafilter is a great addition as you can see the crema changes right at the source.

We always recommend to prepare some cupping samples in 5 second increments. Pull a shot at 5, 10, 15, 20, 25, 30, 35 and 40 seconds. Now compare the taste of your samples.

  • The 10 second shot probably tastes sour, harsh or too acidic (under extracted)
  • The 20-30 second shots will taste balanced and sweet
  • The 40 second shot starts tasting bitter and burnt (over extracted)

If the Espresso Tastes too Sour try:

  • Use a darker roast colour
  • Increase the extraction time
  • Increase the dose (amount of ground coffee)
  • Increase the shot size (amount of water)
  • Grind finer
  • Tamp harder
  • Increase the Brew Temperature

If the Espresso Tastes too Bitter try:

  • Use a lighter roast colour
  • Decrease the extraction time
  • Decrease the dose (amount of ground coffee)
  • Decrease the shot size (amount of water)
  • Grind coarser
  • Tamp lighter
  • Decrease the Brew Temperature

The strength of a cup of coffee can actually be measured. During extraction, oils and solids end up in your cup and can be measured as TDS (total dissolved solids).

We looked at the TDS measurements throughout the extraction time (40 seconds). Most extraction curves look something like this:

Brew Temperature:

While the brew water temperature has a huge impact on the extraction of the oils and solids (aroma), most espresso machines won't let you adjust the water boiler temperature. This requires a PID (Proportional Integral Derivative) controller to adjust the boiler temperature. On average, the brew temperature is set to 200F. The ideal brew temperature depends on the coffee bean, roast colour and desirable taste profile. Generally the higher the brew temperature, the more bitter characteristics are extracted compared to lower brew temperatures which may result in brighter, more acidic taste.

Bottom line:

We hope this quick reference guide will make you realize that at the end of the day you'll need to experiment with all the variables until you find the espresso shot that tastes perfect to you. Adjust only one variable at a time and take notes so you can track your progress and repeat the results.

Sources and more reading:

http://www.home-barista.com/tips/brewing-ratios-for-espresso-beverages-t2402.html
http://www.home-barista.com/tips/espresso-101-how-to-adjust-dose-and-grind-setting-by-taste-t16968.html
http://www.home-barista.com/espresso-guide-skills.html
http://www.espressomyespresso.com/

 



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