Espresso, Volumetrics, VST mojo


Volumetrics - 

Volumetric espresso machines use a Paddle Wheel Meter to control the volume of water that is used for a shot of espresso. When used correctly, volumetrics are a barista’s best friend. 

Since the introduction of Synesso espresso machines with paddle controls, there has been a trend towards giving the barista “more control” over the length of a pour. This is great, but we are only human. It is incredibly hard to judge an accurate volume of espresso by eye, especially while managing a busy café environment. 

Using volumetrics on your espresso machine will remove this complicated variable from your in-service process, giving you more time to focus on other matters. 

Unfortunately, volumetrics are not a ‘set-and-forget’ solution. To use them correctly requires a good knowledge of brewing ratios and espresso extraction. 

VST Baskets - 

Espresso baskets have recently been identified as a major source of inconsistency amongst all espresso machine manufacturers. Until very recently, all espresso baskets have been manufactured the same way - either with drill bits or punch presses - which create uneven hole sizes with uneven distribution. This leads to an uneven extraction of the coffee grounds and, subsequently, we don’t get as much out of our coffee as we could. 

VST Baskets have been redesigned from the ground up to be extremely consistent, accurate and durable. They are warranted for zero defects for a year of commercial use and are supplied with a quality scorecard, unique barcode and microscopic screenshot. They are, without a doubt, the best baskets available on the market right now. 

There are 5 different sizes of VST baskets – 7, 15, 18, 20 & 22g. After testing these baskets as espresso and cappuccino (160ml cup) we have found that the 20g baskets provide the best strength of beverage. The 20g VST basket is designed to hold 19-‐21g of coffee (and so, yield between 27 and 34g of espresso). Any more, and the grounds will begin to press on the showerscreen; this will create an uneven saturation of the puck and will negate any advantage created by using the baskets. 

Compared to standard La Marzocco and Synesso baskets, the hole size of the VST’s are much larger, creating less resistance. This means the user must use a finer grind to keep their extractions within the 22-‐30 second window. Do not be tempted to use more coffee to “slow down” the pour. As mentioned above, these baskets are only designed to use 19-‐21g of coffee. 

Do not be alarmed if your tamper sinks lower into these baskets, if your espresso shots look quicker towards the end, or if the pucks look wet when you remove the handle from the machine – if you are hitting the prefered dose, yield and time for that coffee, it will be delicious. Also, these baskets are much deeper than standard La Marzocco or Synesso baskets -‐ when you disengage the pump, there is more headspace above the coffee, and so more water will be sitting on top making the puck look wet. 

VST baskets do not have a very high tolerance for mistakes by the barista. It is absolutely essential to maintain the same dose +/-‐ 0.5g for every handle. It is also very important to ensure all of the grounds are evenly distributed throughout the basket and your tamper fits snug within the edges (58.4mm). If there are mounds and divets in the grounds, once tamped, they will become areas of lower and higher water flow respectively. If even distribution is not achieved, the benefits of using these baskets are once again negated. 

Even so, these are only slight drawbacks compared to the dramatic improvements in both flavour and consistency across the board. 

Brew Ratios 

Espresso coffee has 3 main variables in regards to brewing ratios. In order of importance - 

1. Dose – The amount of coffee used in the basket (measured in grams) 

2. Yield – The weight of the double espresso, in the cup (measured in grams, NOT mls) 

3. Grind – The fineness of the grind (influencing total extraction time and measured in seconds) 

A brewing ratio is the difference between the dose and yield weights, and can be expressed as a percentage, or decimal; whichever is easiest for you! 

Eg.1   A 20g dose, resulting in a 30g yield = 66% or a ratio of 1.5 

(20g/30g) x 100 = 66% OR

20g x 1.5 = 30 

Eg.2   A 18g dose, resulting in a 25g yield =72% or a ratio of 1.4 

(18g/25g) x 100 = 72% OR

18g x 1.4 = 25 

For most Sensory Lab coffees, a brewing ratio between 60% and 70% (1.4 and 1.6) is recommended. 

The next variable to add to the mix is grind. Without a method to control the speed of extraction, a consistent brewing ratio will not always give you good results. 

From our own experimentation, we have concluded that an espresso shot can taste delicious anywhere between 22 and 34 seconds. A longer extraction will generally create more intense flavours and denser mouth feel; while a shorter extraction will create softer flavours and a lighter mouth feel. 

When dialing in an espresso, it is very important to decide on a dose first; and then manipulate the grind and yield second. If a specific dose has not been decided on, it is very difficult to make decision about grind changes. This is because dose also affects extraction time.

Eg.  A 20g dose and a grind setting of 5 will yield 30g of espresso in 30 seconds. (grind setting # is arbitrary for example purposes)

If you change the dose to 18g, a grind setting of 5 and yield of 30g will take only 22 seconds. This is because there is a lot less coffee in the basket providing resistance to the pump pressure.

Once you have decided upon a dose to use (20g in this example) ; follow these steps to determine yield and grind. Note you will need to have  a small set of scales that have an accuracy of 0.1g and a timer or stopwatch. 

Use a small set of scales to tare your espresso cup.

Grind and tamp a handle with 20g of coffee, insert into the machine. Make sure the grounds are evenly distributed around the basket, and tamp it.

Place the cup and scales under the espresso machine’s spouts.

Start the pump and a stopwatch

Stop the pump and stopwatch when the scales read 3 grams below your desired yield weight ( due to the lag in the scales and coffee still coming out of the machine)

Once finished, your double espresso should weigh between 1.4 and 1.6 times the weight of your dose( in this example, between 28 and 32 grams)

If you reached the targeted yield before 22 seconds, adjust the grind finer.

If you reached the targeted yield after 30 seconds, adjust the grind coarser.

Repeat this process, adjusting your grind until you achieve the desired yield within 22 to 30 seconds( or more precisely if so desired)

In short time, you will see the direct relationship between large & small grind changes and their effect (in seconds) on the extraction. This can only happen when your dose stays the same.