Josuma Coffee Company

Most Espresso Machines in North America are Configured for Production Speed Rather Than for Espresso Quality

Espresso machines are expensive pieces of hardware, costing from about $3,000 to as high as $15,000 for a two-group machine.  Quite often it represents an important portion of ones investment in an espresso bar.  In any case, it is a critical part of ones operation and if the machine goes down, you are essentially "out of business."

Despite their high costs, these machines perform only three basic functions: First, they heat up the water to between 195 deg F and 205 deg F for making espresso.  If that is all that was required, one could accomplish it using a stove and a kettle.

Second, they pre-measure the amount of water delivered to the porta filter when a particular button is pressed; the exact amount of water depending on how that button is programmed. If that was all that was required, one could use a stove, a kettle and a measuring glass.  

Unfortunately, most machines are programmed to deliver too much water, some as much as 4 oz when making a double shot of "espresso."  This is based on the mistaken belief that more is always better.  We will address this problem in a future newsletter.

Third, they deliver the water to the porta filter under pressure; pressures as high as 10 bars or 140 lbs per square inch.  Without this high pressures, one simply cannot make real espresso.  The stove top devices that claim to make "espresso" at home seldom develop pressures above 2 bars and are incapable of producing espresso of any kind.  At best they produce strong coffee.

Using Water Pressure in the Wrong Way

Most practitioners of the art of espresso outside of Italy, employ the pressure generated by these machines in the wrong way. Instead of using it to drive the oils out of the ground coffee, they use it to speed up the passage of water through the coffee so as to make the "espresso" in 14 seconds, or less.  If it takes less than 20 seconds from the time the button is pressed till the end of the pour, one simply cannot produce real espresso, only ordinary coffee.  

The machine people have only helped to exacerbate the problem by speeding up the delivery of water so as to make the "espresso" in shorter and shorter times.  Most of the machines are reconfigured for production speed rather than espresso quality before they are shipped to North America or installed here.

When hot water comes into contact with the ground coffee in the porta filter, some portion of the ground coffee simply dissolves in the hot water.  Actually, one fifth of the ground coffee, by weight, is soluble in water and ends up in the cup.  Ideally, only about two ounces of liquid should have been produced in making a double shot of espresso and will be about five times as strong as ordinary brewed coffee.

Real purpose of the water pressure is to drive out the oils that are present in the ground coffee.  These oils just do not mix with water.  Instead, they form tiny droplets and swim in the coffee concentrate. This dispersion of oils in the coffee concentrate constitute an emulsion; and it is this emulsification of oils that actually converts strong coffee into real espresso.

Emulsifying the Coffee Oils

When oils in ground coffee are emulsified, all measurable properties of the liquid are changed.  Density, viscosity, surface tension, flow rate, wetting power, foam forming ability, of espresso are all different from those of ordinary coffee.  Real espresso is in fact a very different liquid, not coffee any more.

So are all the flavor properties.  For example, when one takes the first sip of real espresso, the oils in the emulsion coat one's taste buds and thereafter one's ability to detect bitterness is markedly reduced.  Thus, the second sip will be less bitter and the brain will use this information to interpret the second sip to be sweeter.  Hence, if one make real espresso and ordinary coffee using exactly the same blend, the espresso will be a whole lot sweeter. 
Improper Dosing & Tamping
The process of pressurizing water results in packing energy into the water molecules.  In the process of making real espresso, this entire energy must be used to break the bond between the oil molecules and the ground coffee particles and drive these oils out.  Once that is accomplished, there should be little or no energy left in the water for it to gush out of the porta filter.  The resulting brew should simply ooze out of the porta filter like molten chocolate (see photo).

If one does not succeed in driving the oils out, there would be too much energy left in the water as to make the liquid coffee gush out of the porta filter with the characteristic noise one hears at most espresso bars in North America.  

Assuming you are using a blend that is specifically designed to produce quality espresso, the secret then is to grind the coffee fine enough and tamp it hard enough so as to impede the flow of water through the coffee puck.  Instead of gushing out, the pressure should be used to force the water to penetrate the interior of the ground coffee particles and dissipate all its energy in driving out the oils, in addition to extracting the solubles.
What Is a Gicleur? Why Is It So Important?


A properly designed espresso machine has a restricting aperture inserted into the path of the pressurized water to control the amount and rate of its flow.  The technical name of that device is "gicleur."  Although it is often referred to as the "gicleur valve," it is not a valve at all; instead it is a limiting aperture, normally between 0.6 mm and 0.8 mm in diameter.

The gicleur plays several important roles in the functioning of a properly tuned espresso machine.  First, it limits the amount of water that flows into the porta filter in a given period of time.  Slowing down the flow of water is important for production of quality espresso.  Always remember that making espresso is not a speed contest.

Second, it protects the coffee in the porta filter from being blasted by the initial pressure wave that emanates from the pump as soon as it is turned on.  This pressure wave travels down the tubes and impinges on the top of the coffee in the porta filter if the restrictor is not in place to dissipate this wave.  In the absence of the gicleur, the initial blast of water creates a crater on the top of the coffee puck, thereby making the center portion of the puck much thinner than the surrounding portions.  This causes most of the water to channel through this thin coffee in the middle of the puck.  When that happens, the resulting liquid will be weak and bitter because the center portion of the puck would have been over extracted and the surrounding portions of the puck left under extracted.

When the gicleur is installed, the 140 lbs/square inch pressure wave reaches the pump side of the aperture, and the entire pressure drops across this orifice, with the pressure on the other side being zero.  As some water passes through the aperture, water pressure slowly build up behind the aperture, on top of the coffee.  Thus the water pressure that the coffee is exposed to builds up gradually from zero to 140 lbs/square inch with minimum disruption of the coffee puck surface.  This gradual build up is important to maintain the integrity of the puck for quality espresso extraction.

It is not uncommon for the gicleur to be opened up to 2 mm or larger or to be left out altogether when people focus on production rate rather than on espresso quality.  Some of the espresso machines used by the large chains fit this description.  

The simplest way to determine if your machine is equipped with a gicleur is to make a "water debit" measurement.  This is a very simple, common sense based, concept and is described in the next section of this news letter. Though based on common sense rather than exact science, it is nevertheless a very useful measurement to make.  

Measuring Water Debit

Water debit is the volume of water coming out of the group head during the first 10 seconds of the pump being turned on. It is that simple.

Follow these steps to measure water debit:
  1. Remove the portafilter from the group head and purge the group head a few times by turning on the pump and allowing the water to simply flow out. 
  2. When the group head is sufficiently free of spent grounds, place the portafilter locked in position with no coffee in it.  
  3. Run the pump for a short time and turn it off. Wait for about 20 seconds.
  4. Now turn the pump on and collect the water in a measuring glass for 10 seconds.
  5. Note the amount of water collected in those 10 seconds
Ideally the "water debit" should be 2.5 oz. It can vary between 2.0 and 3.0 oz. If your machine is configured for speed, as many machines in the US are, the readings would be higher.
If water debit is much higher than 3.0 oz, either the pump pressure is too high, or the gicleur valve is too large or non-existent.  See if you can reduce the pressure to 8 bars and/or install a gicleur valve of about 0.6 - 0.8 mm in diameter.
Note: The pump pressure should be read when the pump is on and can be read either during the water debit measurement or in a subsequent run of the pump.

As always, we appreciate your interest and support.



JJ Photo
Dr Joseph John
Josuma Coffee Company
P.O. Box 1115
Menlo Park, CA 94026
Tel: 650-366-5453