How Al's Rule Saved My Life

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#1: Post by jrtatl »

How Al's Rule Saved My Life
By Jeremy R. Thompson

I knew if my espresso didn't get better my wife would kill me for having spent so much money on equipment, only to produce lip-puckering swill. I thought I knew the basics: grind, dose, distribution, tamp, cooling flush, lock, shoot, watch for blonding, cut the shot. And, in a way, I did know the basics. I read about them over and over again on the Internet.

After continued research and experimentation, I discovered that I did not know how to properly apply the basics that I had learned on the Internet to my setup at home. Everything changed the day I discovered Al's Rule (or Al's Sweet Spot Rule). My espresso improved, and my life was spared.

The following is a brief introduction to Al's Rule and how it can be used at home. I assume that the reader is familiar with, and has mastery of, the basics mentioned above.

"Al's Rule" is a rule of thumb formulated by Al Critzer, a longtime espresso expert. As he published on circa 2001: "the perfect espresso is 30ml in 30sec. That's assuming that all other factors are in line." By extension, the perfect double espresso will be 60ml in 30sec. (The design of the double basket allows for the increased volume in the same amount of time). If you think about it, Al's Rule is really just another, more precise, iteration of the "Golden Rule" you've seen posted on the Internet: double shot in 25-30sec.

I only make doubles, so I am concerned with achieving 60ml in 30sec. Why 60ml? Why 30sec? Because the Italians say so! See the Italian Espresso National Institute definition.

60ml pour

60ml shot in 30sec

Fortunately, Al's Rule allows for reasonable variations in volume. I like the flavor and texture of double ristretto (less than 60ml). My wife likes her Americano made with a double lungo (more than 60 ml).

Al said: "For every 5ml of espresso above 30ml, subtract 1 sec of extract time." So, by extension, when making a double, for every 10ml of espresso above 60ml, subtract 1 second of extraction time.

70ml pour

70ml shot in 29sec

Al said: "The same holds true in reverse. This will find the sweet spot in espresso regardless of volume in the cup (within reasonable limits of .75oz to 2.5oz), as you are optimizing extraction of the desirable elements, maintaining the balance between under- and over-extraction."

50ml pour

50ml shot in 31sec

So, my 50ml ristretto should extract for 31 seconds. The 90ml lungo I make for my wife will need to extract for only 27 seconds. The reason for this is simple. If I desire a greater volume of espresso, I will be running more water through the coffee grounds. In a gross overgeneralization, each molecule of water needs to touch the coffee grounds for less time, otherwise the grounds will over-extract. If I desire a lesser volume of espresso, less water will be forced through the grounds. So, each molecule of water needs to stay in contact with the coffee grounds for a longer period of time, or the grounds will be under-extracted. (This is not meant to be scientifically valid, merely illustrative)

Before anything else, I had to accept that Al's Rule is merely a guideline. So, experimentation was key to finding out what works best for me.

I started out by making sure that my dose (weight and/or volume of grounds) was completely consistent from shot to shot. Variations in dosage make for variations in shot timing and volume. So, I control this variable by using either a digital scale, or using the same volume of beans each time.

Once I was dosing consistently, I worked on my distribution and tamping. There are several techniques out there, and I settled on one and stuck with it. I dose halfway, settle the grounds, overdose the basket, and move the mound of grounds around the basket so that an even surface covers the entire basket. Then I level off with a straight edge. Then I tamp to 30lbs, with no twisting and no polishing. I then lightly blow the loose grounds off the top of the puck. I use this same procedure every time. Variations in tamp cause variations in shot timing and volume. Keep distribution and tamping consistent, and there is one less variable to deal with.

I use my grinder to control my shot volume and timing. With a commercial or prosumer espresso grinder, particle size is adjustable. Here's how I dial it in:
  1. First, I load my consistent dose into the grinder. Grind a shot. Distribute and tamp per usual. Then, I pull a shot, cutting it at 30 seconds. I note the volume of the shot when I cut the pump.
  2. Generally, if the shot volume is above 60ml, I will adjust the grind finer. If the volume is below 60ml, I will adjust the grind coarser.
  3. After adjusting the grinder: Grind, dose, tamp, pull. Cut the shot at 30 seconds. Check the volume. If the volume is still above or below 60ml, tweak the grinder again.
  4. After the grinder adjustments yield 60ml of espresso in 30 seconds, I stop tweaking (for the moment).
The beauty of Al's Rule is evidenced only after I have my grind dialed in to the 60 in 30 ideal. When I wake up the next morning, my grind will be off slightly, due to many factors. I can still get a great shot just by watching the pour as it leaves the portafilter. If it starts by dribbling a bit, and then proceeds to a slow stream, I know my resulting volume will be low, so I need to increase the time of the pour. If the shot starts out with a steady stream, I know my resulting volume will be larger, so my shot time has to decrease.

A good feel for Al's Rule also helps when I try to judge a shot based on volume in the cup. If my cup is filling fast and it looks like my shot volume will be high, I cut the shot early to preserve Al's Rule. Conversely, when the cup is filling at a snail's pace, I let the shot run long.

After I got a feel for Al's Rule, I was able to relax, and stop timing every shot. I generally time enough shots to get the grind dialed in. Then, I can pull shots based on feel, and tweak the grind (and time the shots) as necessary.

I just remember that low volume shots should take longer, and high volume shots should take less time.


UPDATED: From March 23, 2000 post from
Al Critzer wrote:It seems that everyone's close, but pretty much all around it. As I was trained, the perfect espresso is 30ml in 30sec. That's assuming that all other factors are in line. For longer extractions, the contact time of water to coffee would have to be lessened so that undesirable elements associated with overextraction wouldn't be present in the cup. With shorter extractions, the water to coffee contact time would have to be increased to ensure that underextraction doesn't occur. This is accomplished by grind adjustment. A good rule of thumb I have developed is this: For every 5ml of espresso above 30ml, subtract 1 sec of extract time. By this formula 11/2oz (45ml) would require 27sec extraction, 2oz (60ml) would require 24sec, etc. The same holds true in reverse. This will find the sweet spot in espresso regardless of volume in the cup (within reasonable limits of .75oz to 2.5oz), as you are optimizing extraction to the desirable elements, maintaining the balance between under- and overextraction. For some reason, grinder adjustment and it's crucial impact on espresso is the most difficult concept to explain and grasp in all the trainings I do. As to ristretto. This a different drink altogether. If your grinder is set for regular espresso, and you choose to stop the pour at 25ml, this is simply an underextracted espresso. You haven't hit the sweet spot yet. The " restricted" part referred to as ristretto is not so much related to volume as it is to water flow through the coffee puck. The ristretto that has been used for cuppings is a 25ml cup in 30-35sec. This extraction intensifies the organoleptic perceptions of the eyes, nose, taste buds and upper palate to better isolate the positive attributes of a given blend. Where the positives are accentuated, the negatives are exacerbated as well. The extractions are characterized by a very thin mouse's tail with rich, dark brown crema. Most people don't drink this as their everyday drink, but it is helpful in developing blends. If you customarily drink 25ml (or 50ml doubles), your grinder should be adjusted accordingly. Damn, I did it