FRCN Espresso "HOW TO" Pages
by Randy Glass - Copyright 2008-2013
E-mail me at email@example.com
EASY GUIDE TO BETTER ESPRESSO AT HOME
by Randy Glass
©2008-2013 - Updated 11/19/2013
WARNING and DISCLAIMER - This article is general in nature. It covers functions of espresso machines, cleaning procedures, and various procedures that may or may not apply to your equipment. As always, consult your owner's manual for details on how the following article may or may not apply to your espresso machine, espresso grinder, and other equipment you may possess. Improper application of the following procedures my create a safety hazard and may cause bodily injury or damage to your equipment. By reading and/or following the information in the article below you assume full liability and responsibility for any and all damage or injury the information in this article may cause, whether used correctly or incorrectly. If you do not agree to these terms you must leave this page now.
NOTE- This article will be an ongoing effort. If you find an error of omission or an error of commission, please feel free to E-Mail at firstname.lastname@example.org . Additionally, this article, when speaking of making espresso, refers to a double, two-ounce (60ml) espresso.
Navigation Tip: These links: - TOP - conveniently located throughout this article will bring you back to the above Table of Contents.
INTRODUCTION Espresso will humble you. Just when you think you have a handle on things and you are making some very nice coffee drinks, BAM! Things fall apart. Or you were happily trotting along, tra la la, thinking you were making good espresso, and then you sample some made by another barista and you discover there are worlds of taste beyond what you had previously experienced or imagined. Now what?
I began this article shortly after dealing with a problem of my own. My espresso became mediocre, and that is being kind. It was drinkable in milk, but rude on the palate when sampled straight. I finally realized that there was channeling causing the flow to turn watery and blond early in the extraction. I could see the defect in the puck. What to do? What was causing the channeling? Back to basics!
But it's not just me. We all run into espresso difficulties now and again. There are so many variables to making espresso that when something goes wrong it can be intimidating and confusing trying to decide what to do. Should you adjust the brew pressure or just grind finer? Are you tamping too hard or is the coffee stale? This article is aimed at giving you the knowledge to recognize and fix problems when your espresso goes off, but it also quite valuable as a guide for those who are just starting out. I hope that it will help you avoid some of the pitfalls that we all encounter along the way.
By no way should this article be taken as an all-inclusive guide that will solve all problems you may encounter when making espresso. It is merely based on my experience making espresso at home since late 2000, and all the mistakes I have made and could remember while writing this article.
In much the same way that this is not an all-inclusive set of instructions, I will add that you do not necessarily have to do everything included here, nor do you have to do these things in the way they are described. I have had excellent espresso from a machine where the coffee was just dosed into the basket to about half the dose you would expect, left untamped in the basket, and locked into the group and extracted. You need to apply those portions of the following information that work for you in a way that works for you.
I will add that this article is intended to assist two groups of people: the first are those who are new to espresso and desire to build a sound foundation so that their future endeavors in the world of espresso will be as successful as possible. The scientific method applied here would state that if you control all the variables, it makes it a lot easier to avoid problems and to diagnose them when they do occur. The second group are folks who are having difficulties with their espresso and are trying to find out what went wrong.
EXAMINING YOUR ESPRESSO Lock and Load! "FIRE IN THE HOLE!" You hit the brew switch, or pull the brew lever and the espresso begins to flow. Is that pull going to taste good? Will it be coffee nirvana or "Tincture of Coffee"© ? How do you know? If you take your espresso straight then you will probably have a good idea very soon... as soon as you sip! If you just drink milk-based drinks I highly recommend keeping a demitasse spoon next to the espresso machine and that you take sampling sips of the espresso streams. If you have never experienced a really good espresso or are not sure how it should taste, you can read my Beginner's Guide to Tasting Espresso to get started.
We often read about the "rules" of espresso, and sometimes it is referred to as "The Golden Rule," but this is not to be strictly followed. That "2 in 25" rule says that you should get about two ounces of espresso produced in about 25 seconds from the time that you begin the pull. This is just a very rough guide. Some machines start with a slow, gentle flow of water until the pressure builds, so for those machines 25 seconds will be somewhat of a too-fast extraction. I have had some nice 30 and 35 seconds extractions. I have also had some very drinkable 2.25 to 2.5 ounce pulls. Through all of this you should never forget that espresso is a food product, it is meant to be consumed, and so the only rule that really counts is the taste.
Viscosity is an excellent indicator. The flow should start slow and thickly and build to a flow that stays quite viscous. If the flow turns watery and light in color there could be a problem. If you have a bottomless portafilter you should watch the flow occasionally, particularly if there is a problem with the taste. The flow should start evenly across the entire basket at about the same time and should center as one flow in the middle of the basket. Areas that do not flow or uneven streams can be a sign of a dose, distribution, or tamping problem and may even indicate a problem with your grinder.
The color of the flow is also an indicator. This is also best observed using a bottomless portafilter. As seen here, the streams should have striping in the actual flow. The flow across the bottom of the basket should show distinct striping. Even when things are going well it is a good idea to watch the bottom of the basket so that you have a reference point to which you can refer in the future when there is a problem.
After the pull is done and you remove the portafilter, examine the puck before you knock it out. Are there any holes, divots, or crevasses? This could be a sign that there was a problem with the amount of coffee used, or the distribution or tamping which caused or led to channeling. But remember that what is happening at the bottom of the basket (seen above), and in the cup is far more important than the appearance of the spent coffee after the extraction has ended.
FIX IT When something goes wrong and your espresso is in some way disappointing, it is a good time to stop and examine the basics to rule out any of the simple things. So let's go through the process and see where errors can occur, their common causes, and how to remedy them.
Before beginning you need to be aware that so many things in the creation of an espresso are interrelated that it can be very difficult to single out one factor as the cause. For example, is the slow extraction caused by too fine of a grind, too low brewing pressure, too much dust created by worn burrs, or all of these factors? Is the bitterness caused by too coarse of a grind or too high water temperature?
If you intend to make use of this article to improve your espresso, the use of some common sense and logical thinking skills are critical. If the espresso was good and now it isn't, something has changed. Logically, if everything is done exactly the same way, every pull, and the espresso has changed, what could be the cause?
The process can be broken down into four general areas.
In no particular order they are:
Coffee - Equipment - Procedures - Water
They are all interdependent. You cannot make good espresso with bad water. The best equipment money can buy cannot make good espresso with stale beans. While the majority of this article deals with the procedures used to make espresso and how to modify them to improve your product, I also discuss the other three factors as well. My main goal here is to help you discover problems in your procedure and to make the best possible espresso with the equipment you currently have.
COFFEE Espresso is created when a specific process is applied to coffee and water. Virtually all the flavor comes from...? Anyone...? Yes! The coffee! It's all about the coffee. How old is it? Is it a new batch? New crop? New roast? New blend? Has it been sitting around longer than usual? Do you really know how long it has been since it was roasted? If something changes, particularly if it coincides with a change in your coffee (like opening a new bag or starting a supply from a new source) suspect the coffee first.
If your coffee is coming from bins at the supermarket or in vacuum sealed bricks then I can just about guarantee that it is stale. Even if the coffee comes in some special packing like nitrogen-filled cans under pressure, a lot of time has probably passed between the time it was roasted and when you opened the package at home. Some of these packed coffees will taste good the day they are opened, but once exposed to the air, the oxygen-hungry beans stale very rapidly. A day or two later they can taste as old as they actually are.
Fresh Coffee is Critical!
DOSE For most of us (probably about 95% of those reading this article) the creation of an espresso is a hands-on experience, and so let's begin with the dose— the amount of coffee you are using. The "dose" can be thought of as a verb and a noun. There is the action of "dosing" when the coffee is being dispensed as well as the amount of coffee you choose to dispense and use which is the "dose."
When the portafilter is locked into the brewgroup, there has to be some space left between the top of the coffee and the shower screen, and adjusting the dose adjusts that space. If there is not enough space, when you lock the portafilter in place the coffee is disturbed as it hits the shower screen or the screen's retaining screw. Coffee also expands during the extraction and there needs to be a bit of room for that as well.
If the structure of the compacted coffee is disrupted, either before the extraction begins or during extraction as the coffee expands, the result will most likely be channeling and poor extraction. Channeling is when the water takes the path of least resistance through the coffee instead of flowing through it evenly so that it can thoroughly extract all that the coffee has to offer. Overdosing (using too much coffee) also can make a bigger mess on the shower screen.
If you use too small of a dose (too little coffee) you are under-dosing. If you don't use enough coffee the espresso can become blond too early in the extraction process and the result will be a beverage that has thin body (watery) and possibly be bitter. To little coffee requires a too-fine of a grind which may place a lot of fines into the cup which is yet another source of bitterness.
It can be so easy to slip into old habits (or develop new, bad ones). Just before I created the first version of this article I found that I had been overdosing (using too much coffee). It wasn't by much, but it was enough that it caused channeling as described above. There are many factors have to be aligned to the amount of coffee you are using, so having the "correct" amount of coffee and being able to dose that amount every time can be a cornerstone when diagnosing problems.
Not too much... Not too little. How can you tell? Begin by doing this simple test:
Those with doserless grinders will have to deal with how their grinders spit out the coffee. Move the portafilter around to get the coffee distributed as evenly as possible.
If there is ANY sign of clumping, apply the WDT (Weiss Distribution Technique discussed below in the DISTRIBUTION section of this article).
NOTE: As mentioned in the introduction, some of the above steps may not be necessary for all users. For example, if you have a grinder that creates a very even, clumpless grind, you will not need to tap the portafilter to settle the grounds nor will you need to use the WDT.
Verifying That You Used the Correct Dose, and How to Adjust the Dose.
Place a nickel or similar coin in the middle of the puck and do the same lock-and-remove test again. The result should be the same- at the most, there should be a slight mark from the nickel in the coffee, but the puck should not be disturbed beyond that. A slight mark is OK, but there should be no cracks or heavy dislodging of the coffee. If no mark is left, add a dime to the nickel. If no mark is produced with that test you will need to use a bit more coffee.
Too much coffee will cause the shower screen or the retaining screw to damage the integrity of the compacted coffee. The puck will be damaged before the water begins to flow with the resulting channeling of the flow of water through the coffee taking the path of least resistance. The result is espresso with thin body and thin crema. The espresso will flow like water from the spouts instead of like warm honey. If the procedure above indicates that you have used too much coffee, try this:
Using too little coffee and the flow may start slowly and thickly, but will turn blond and thin in as little as five or ten seconds. There is a narrow range as to what works best. As you become more adept at making espresso you will be able to adjust the dose to match your equipment, your coffee, and your taste.
Using more is easy to achieve. Just add more coffee. But if you find you have been using too much coffee, it can be tricky to remedy. Some grinders create a very fluffy grind, and so you might find that a swipe across the top of the basket with a straight edge works best. Other grinders create a dense grind and you may need to swipe deeper.
So, depending on your espresso machine's shower head, the basket depth, how deep the portafilter fits into the brewhead, your grinder, and the coffee and grind you are using, you may need to make adjustments to your dose. You may not need to do this at all if you have a grinder that has an accurate timer that grinds exactly the right amount every time. How do you know if it is the right amount? I recommend doing the "Lock and Remove" test on a regular basis to be sure that you are staying on track.
Fine Tuning The Dose
DISTRIBUTION How the amount of coffee is distributed in the filter basket is very important. Dosing the coffee and distributing it in the basket coincide and intermingle. Even if you have the correct mass of coffee, if it is a mountain in the middle or there is more coffee on one side of the basket than the other, the flow of water will be uneven it may actually disrupt the puck causing channeling once again.
The first step in avoiding this is to dispense the coffee into the basket carefully. I like grinders with dosers because the barista can operate the dosing lever at the rate which matches the way they ork. A doserless grinder will send the coffee forth at the rate determined by the size of the burrs, the grind setting, and the motor's speed. An additional benefit of using the doser lever is that it can be clicked rapidly while the grinder is working, dispensing small amounts of coffee as it falls from the grinder's throat, and that action tends to break up clumps before they can be deposited into the portafilter. The coffee falls like a drizzling rain and not a hail storm. How effective that is depends to some extent on the grinder you choose.
I grind per shot. I repeatedly thwack away at the lever so that small amounts of coffee are ejected from the grinder into the basket with each click. All the while I am moving the portafilter around to get the coffee distributed as evenly as possible. Although it is difficult to achieve, the goal is to have the coffee evenly distributed and level across the top. Realistically, just try to get as close to that as you can. Beyond that, try to develop a procedure that you can repeat every time.
Does your grinder create clumps? Some grinders are clump-free and others not so much. Some factors such as the humidity, static in the grinder, moisture level in the coffee, grind, chute design, materials used in construction of the grinder, etc., can combine to create extreme clumping. If your grinder creates clumps then you may need to use the Weiss Distribution Technique (WDT). After filling the portafilter with ground coffee, use a sewing needle, thin straightened paper clip, dissecting needle or other similar tool to stir the coffee in the portafilter.
As shown in this illustration, I find that using a pattern of intersecting circles as you go around the basket to be effective. When accomplished with attention, this procedure will also assist in leveling out the distribution of coffee as well as breaking up any clumps. The added benefit of this procedure is that it tends to fluff up the coffee. You may find that, after WDT'ing you may be able to simply level off across the top of the portafilter and that will create a good dose mass. This will be apparent when you tamp. Remember that all these procedures are interdependent, so after changing the way you distribute you may have to change the dose or grind.
Regardless as to whether you swiped across the portafilter, weighed the coffee, used the WDT, or any combination of procedures to dispense, dose, and distributing the coffee, it is possible that the coffee is not the same density throughout the basket yet. Distribution can be easily improved now by striking the entire portafilter downwards on the counter top. As mentioned previously, this should be done gently. Two or three light taps from an inch or two above the counter is sufficient. This give the coffee a chance to settle and level out before the tamping procedure which comes next. I use a tamping mat which not only protects my counter top but also absorbs a bit of energy making it easier to be gentle. A scrap of dimensional oak works as well. After this downward tapping you should find the coffee level. If not, it means that you did not dose or distribute the coffee evenly. Dump it back into the doser (or into a suitable container if you have a doserless grinder) and begin again. Never run ground coffee through a coffee grinder!
TAMPING Tamping the coffee helps assure that the coffee puck is the same density throughout and affords an even resistance to the flow of water. Water takes the path of least resistance, and if there is an area of lesser coffee density, the 130 PSI (9 BAR) of water pressure will find that area quickly and channeling will be the result.
The choice of tamper is important. The most important decision is to get one that properly fits the basket you use. It should be as close of a fit as possible without binding. Some say that it's shape (the shape of the tamping face) should match the shower screen, and there are convex and concave shapes from which to choose. I used an inexpensive, one-piece aluminum, flat tamper for many these years and it worked fine. Feel free to experiment, but flat is a good way to go if you are not sure. There are also tampers with etched or engraved, parallel lines around the outer edges of the base. This shows not only that your tamper is being held straight in the basket but also is a quick way to verify the depth to which you are tamping which is an indication of consistent dose.
There are so many theories concerning tamping that you could ask ten baristas and get eleven answers. Here is some information that will help you find what works best for you:
(damaged shower screen, missing shower screen or dispersion device, poor design, etc.)
If you are unsure what amount of force you are using I suggest getting out a scale. The bottom line is that, within reason, it doesn't matter much— at least to say, of the factors over which you have direct control, tamping force probably has the smallest affect on the espresso. If you find that a specific tamp is required, particularly one that is quite high or quite low, it is possible that you are compensating for other problems.
Tapping the Side of
A challenge: If you want to test your dosing and tamping skills, carefully and gently turn the portafilter upside down. Do this over the doser or over a bowl! If all has gone well up to this point, nothing will happen other than the remaining loose bits of coffee on the portafilter will fall off. If all has not gone well up to this point, the coffee will fall out of the portafilter and you will need to begin again. I hate when that happens!
TIP: If you have a bottomless portafilter it can be difficult to hold it steady when tamping. I use a tamping mat on the edge of the counter. You can also use a piece of hardwood about 3/4" thick upon which to rest the bottom of your bottomless portafilter when tamping. This gives clearance between the portafilter handle and the counter making it easier to hold the portafilter steady. It also protects the counter top. There are tamping mats available which wrap over the edge of the counter which are excellent for this as well.
GRINDER and GRIND
When you have "mastered" dose, distribution, and tamping, (and have stopped laughing after reading the beginning of this sentence... "Mastered..!? He must be kidding!"), the grind is the one adjustment that the barista most often makes to alter the extraction for the best taste. Based on the scientific method of controlling an experiment, you need to keep all factors constant except one— the variable. For any given coffee, once we find a dose mass that works, the grind is the one variable we use to control the extraction.
Let's take a look at the grind range in this way:
The above chart is a generalization, to be sure. I wanted to illustrate that when using a good grinder, there is a range of adjustment that will give acceptable results. In that range is the best combination of factors brought about by the best grind choice. That grind setting is the adjustment that best matches the basket, brew pressure, water flow rate, coffee, temperature, and grind. By adjusting the grind (as well as other factors in the process) you can narrow the range and find the best espresso possible for your situation. The purple, double arrows indicate that the entire range is not set in place. The volume as well as the brew time is adjustable in much the same way. For any given set of evaluation parameters, the best espresso may be at 2.25 ounces in 28 seconds or a 1.75 ounces in 24 seconds. How do you know what is best? Taste it and adjust the parameters to find what you like best.
But how to find that setting? Many problems are created by using a too coarse grind. Why is this a common problem? It might be for fear of damaging the burrs or from recommendations read online or from the manufacturer. Whatever the reason, it is a lot easier to find the correct grind by working from a grinder that is adjusted too fine towards a more coarse setting than it is to work from the other direction. I am not sure why, but in my personal experience as well as the successful advice I have given to many other home baristas, grinding finer has often been the solution when there was a problem with the espresso.
With all other procedures working well (dose, distribution, and tamping), grind finer and finer until the machine is choked or nearly so. That is, until you get about one ounce or less in twenty seconds. Now slowly adjust towards a more coarse setting using the smallest "steps" possible, taste testing after each adjustment. As your skills improve, the "Correct" or acceptable range will be easier to find and will also become more narrow. From there the amount of time it takes to complete the extraction becomes much less of a factor and your palate becomes the best indicator to assist in finding the correct grind. Unfortunately, some grinders will only offer one click finer before the grind becomes too fine or one click more coarse before the coffee is too coarse. This removes an important tool from the barista's hands when it comes to improving their espresso. If you get to that point it is probably time to modify your grinder or replace it.
As I mentioned previously, all the various procedures when creating espresso are interrelated. Don't be surprised if you have to make an adjustment to your dose after changing grind. Knowing what to change and when to change it comes with experience and consistency in your procedures. When you can make a small change in grind, and you can taste that change in the cup, and that change is consistent pull after pull, day after day, you are at a point where you are gaining control over the process.
Note that "gaining" as used above indicating present tense. The fact that we will never have full control over this process is one of the things that has held my interest through the years. Making espresso is easy. Making good espresso is not that hard. Making excellent espresso every time is impossible. The world's best baristas will toss a shot into the sink now and again. Remember that I began this article after nearly 8 years of daily experience at home, and after over ten years I am still learning! I think that the saying, "Pride cometh before a fall" was written by a barista. Just when a great pull comes along, don't be surprised if the next one falls short of your expectations. It happens.
THE ESPRESSO MACHINE
NOTE: Before proceeding with any cleaning procedure or using any cleaning product on your machine be sure to consult your manual or seller.
3-Way Valve - Consult your manual if you are not sure whether your machine has a 3-way valve. If your machine can be backflushed, consult my article 3-Way Valve Hows and Whys. This article covers, in detail, why it is important to backflush which should answer any questions on this process. If you are not familiar with the process, read my lesson on How to backflush. There are a few machines that use a non-standard placement for the 3-way valve, so be sure it is safe to backflush your machine before proceeding with this process.
Internal passages which become dirty with coffee residue may taint the taste of the coffee and can slow the flow of water to the coffee during the brewing process. A dirty 3-way valve can leak creating low brew pressure and can also lead to low water level in the boiler which can damage the heating element or various gaskets.
Steam Wand - Keeping the steam wand clean is simple. When making espresso I always have a dish towel over my shoulder and before beginning each session I wet a corner of the towel with water. You may just want to keep a wet dish rag next to the machine when you are working. This is used to wipe the end of the steam wand off at the end of each steaming session. You should also give a blast of steam after use to clear the wand of any milk that may be in the tip's holes or may have gotten into the wand. I do this regularly and have never had any milk get into the steam wand.
It is also a good idea to remove the tip occasionally. Bits of debris such as hard water deposits can get in there and clog the hole(s) lessening the effectiveness of the steam function.
Brewgroup - The brewhead's area needs to be kept clean. Coffee oils and coffee particles can build up on the screen, behind the shower screen, on the face of the brewhead, and on the brewhead gasket. The cleaning of these areas will vary from machine to machine, so it is difficult to comment specifically. Using a brewhead brush to scrub the area down, flushing some water out, then wiping out the area with the wet towel works fine if done on a daily basis. If your machine has a standard 3-way valve, doing a plain water backflush once a day or once a week (depending on use) and a detergent backflush one a month is usually fine for home machines. More often is somewhat more desirable than less often. If that sounds like overkill, after a week of not cleaning take out the shower screen of a cool machine, wipe your finger across the brewhead, and smell that residue! Notice how easily that dark residue comes off. It can just as easy get into your coffee. If you are still not convinced, taste what you just wiped off on your finger! E-61 machines should not be cleaned with detergent too often as it can cause accelerated wear to internal parts of the brew group by washing out lubricant. Because of that, doing a clean-water backflush at the end of every session is more important than with many other machines.
Shower Screen and Basket - These should be regularly examined. Check for clogged holes, cracks, bad welds, or any other deformity that could affect the espresso. If these look dirty or clogged, soak the parts in a strong, hot solution of espresso machine cleaner. Remove and scrub them with a stiff brush a few times during the soak. If the cannot be cleaned or show damage, replace them.
Removable Parts - Shower screen, shower head (distribution device behind shower screen), filter basket, portafilter body and spouts, and other related parts should be removed from the machine and soaked in cleaner about once every month or two depending on how much use the machine gets. Most machines have the shower screen attached with a screw or bolt. if you have an E-61 brewgroup, Consult my article How to Remove an E-61 Shower Screen and Brewhead Gasket.
As always, consult your owner's manual for details on how to keep your machine clean.
Temperature control is another matter. Manufacturers are beginning to equip some machines equipped with adjustable thermostats, usually in the form of a PID device. Heat exchanger machines have long had the ability to have the boiler's temperature adjusted. Some of the more enthusiastic home users are equipping their own machine themselves with PID controls.
The most important factor when it comes to temperature is to have a machine that can perform the same way from one pull to the next. How you achieve that depends on your machine, the amount of time and effort you want to put into it, and the volume of your bank account. If you have a single-boiler machine then you will likely have to temperature surf, time surf, or add a PID control. Temperature and time surfing methods vary from machine to machine, but basically the procedure involves pumping water out the hot water wand until the thermostat turns on the heating element, stopping the hot water function, then waiting a predetermined number of seconds before turning on the brew switch. More information on this can be found in my Brew-Temperature Control article.
If your machine has a pressurestat you can adjust that to control boiler temperature pressure which is an indirect way to control temperature. The range of that adjustment will affect the amount of steam power as well. Another factor is whether the machine is plumbed or has a reservoir since the temperature of the incoming water will vary. Some machine (such as those with E-61 brewheads equipped with thermosyphon heating) require that some water be bled out of the group before pulling a shot for best results. It is beyond the scope of this article to address how to control temperature in every type of machine. I suggest you consult one of the many online forums for more detailed information concerning the best way to control the brewing temperature of your machine.
Generally, better machines with larger boilers offer greater temperature stability. They also offer the ability to pull multiple shots, one after another, as well as to be able to steam and pull shots at the same time. Better machines with larger boilers also cost more. Machines are now being sold for home use that feature dual boilers— one for brewing espresso and one for steam. As you would assume, these can be quite expensive.
Measuring brewing temperature can be done simply. While not very accurate, it will give you an idea if you are close. Read my How To - Brew-Temperature Check article on how to do that.
If your machine has no adjustment then there is not much you can do about brew pressure. Even if your machine is adjustable, if it doesn't have a gage, the value of the adjustment is questionable. Even machines with pressure gages mounted as "standard equipment" have questionable value as the gages are often of low precision. To make best use of the brew pressure adjustment you will need to either purchase a pressure gage that mounts to a portafilter or cobble one up on your own.
For a machine equipped with the adjustment and a gage, the actual adjustment procedure will vary. Some machines read the pressure a long distance before the brewhead and so the pressure at the coffee will generally be less due to friction loss through the brew path. Since around 9BAR (135 PSI) is the recommended brewing pressure for espresso, setting the pressure at the gage to about 9.5 bar is a good place to start. Without a pressure gage attached to a portafilter there is no other accurate way to judge brewing force.
Having the correct maximum pressure set in the machine will establish a baseline to which the grind will be adjusted. If the machine is capable of sending a maximum 150 pounds of water pressure to the coffee, in order to sufficiently resist the flow of water to get the "correct" volume of espresso in the desired amount of time, you may need to grind finer. This will cause over-extraction and a poor-quality espresso. On the other hand, with the brew pressure too low, you will have to use a too-coarse grind to compensate and this can lead to under extraction. If the machine has a gage, use it regularly to monitor the gage the extraction to assure that you have the correct grind and dose to keep the brewing force from being too high or too low.
At the same time, water that is too high in some minerals (like calcium or lime), will cause mineral deposits to build in the boiler and other parts of the machine which carry water. If not dealt with these can eventually cause blockages, and can even cause the heating element to fail. Water devoid of minerals (processed through distillation or reverse osmosis) may cause leaching of copper pipes and will cause the water level sensors in HX boilers to malfunction leading to a pump that does not turn off, overfilling the boiler.
Minerals will likely build up in the boilers of all espresso machines when water with any mineral content is used. Descaling is a process of sending a special cleaning agent through the boiler to remove the hard water deposits. Citric acid can be used, and there are commercial products for this purpose as well. See my article How to Descale for more information. Jim Schulman's Insanely Long Water FAQ is the best resource I know of for information on water quality and water treatment.
Jim's article talks about the level of total dissolved solids (among many other things). To measure the TDS of your water you can pick up an inexpensive electronic gage. Do a search for "TDS meter" on a shopping search engine or at your favorite auction site. They often sell for around $20 or even a bit less. Even these devices do not tell the whole story. Scaling is a function of general hardness (GH) and alkalinity (KH). Both have to be present to cause scaling. The GH KH Test Kit from API (Aquarium Pharmaceuticals, Inc) is an excellent way to check your water. One test kit lasts for many, many dozens of tests and can be had for about $10 to $15.
Also be aware that if you use softened water the TDS meter is not going to give useful readings. While softening system vary, most exchange scaling mnerals for non-scling minerals, so the pre and post softened water will give approximately the same readings on the meter. That is why I recommend teh API kit.
In all of this, regardless as to how careful and precise you are in attempting to control every step, there will be limiting factors as to how well you can duplicate your last successful espresso. What worked well for your coffee when it was three days old may not work when the coffee is a week old. The brewing temperature range may not be very well-controlled in your espresso machine. The adjustment steps of your grinder may be too coarse. Work hard to control what you can control, and don't worry about the factors that are out of your control.
And there are limiting factors which few ever consider. How about line voltage? We take for granted that the electricity entering our homes is dependable, but is not always the case. Even though my home is on its own transformer, the switching station which feeds it is evidently quite old. For many years the voltage here was about 120 to 122 volts. I assume that something happened at the station during a recent electrical storm and the voltage dropped to around 108-109 when the espresso machine was pulling a shot. This lasted a few weeks until a repair was evidently made and the voltage returned to normal. This not only affected the heating rate of my espresso machine but greatly affected my home coffee roasting appliance!
It seems somewhat illogical, but the entry-level espresso machines aimed at first-time purchasers of home espresso equipment are the most difficult to control and thus are the most difficult with which to create good espresso repeatedly. That is the factor that drives so many to upgrade, or drives them away from espresso. Push your equipment to produce the best it can until you have developed your skills to produce the same flavors as consistently as is possible with what you have.
To a great extent, your level of success depends on your level of commitment. How much effort you put into the process, how much attention to detail you are willing to exert, and how much patience you have. Good espresso is a journey that is ongoing and never ending. The destination is never more than a stop-over, and the journey begins anew the next morning. I have been on the journey for nearly ten years and am still on the road. Have a good trip!
The only way to deal with this is to become as consistent as possible with all the things you do. Eliminating or minimizing as many of the variables as possible will make diagnosing problems a lot easier. This comes from practice and experience. You will never reach perfection. Even professional baristas will toss shots into the sink just from looking at the way the shot issues forth from the spouts.
Here's a good example I recently experienced- I had roasted and just about finished using two batches of coffee from a new supplier but had been having some of the poorest pulls I had experienced in years. While the taste of the espresso was improved with the new beans, the extraction was odd. It started with multiple streams in a doughnut pattern on the bottom of the basket (using a bottomless PF), then joining together in one stream after a good 10 seconds of extraction, then after about five more seconds the flow looked like an inverted bell hanging off the bottom of the basket, and very thin in viscosity. Sort of like the portafilter was trying to blow a bubble that would not release into the air. While I had been getting good pulls producing over 2 ounces of crema with the old coffee, I could not get this to happen with the new coffee.
Mind you, even with this poor extraction performance the espresso tasted better from the very first pull than it had with my old supplier. But what was the cause of these abnormal extractions? It turned out to be overdosing. The new coffee was expanding a lot more than the old supplier's coffee, and I discovered that by dosing less, and the espresso extractions immediately improved.
You may never achieve the level of expertise it takes to know how a shot will taste just from watching the flow from the portafilter, but depending on your equipment, coffee, and level of commitment, you can produce coffee beverages better than available at most coffee shops by using the above information and modifying it to work for you. Remember, all "rules" about making espresso are just starting points. The "art of espresso" is your ability to adjust the rules to get the best possible espresso from your beans, procedures, and equipment.
Hopefully these tips, tricks, and insights will help you make better espresso.
CHEERS, and GOOD LUCK!