Articles From Whole Latte Love

In Depth Look at Frothing Milk

Posted: 08/20/03
4
  1. List of Tools
  2. Basic Equipment
  3. Fundamental Foam
  4. Water is clear. Foam is white. What’s up with that?
  5. Foam you can eat!
  6. Way too much information about Crema
  7. The Gold Standard
  8. Milk Mucilage
  9. White Chrome
  10. Dances With Tips
  11. Frothing Doodads
  12. Super Automatic Machines
 
  1. Practice. Practice.
  2. Seeing Good Foam
  3. Steam is hot. Really hot.
  4. Way too much information about steam tips.
  5. Why You Want Good Foam
  6. Crema comes, crema goes.
  7. What is this Cappuccino stuff, anyway?
  8. Classic Cappuccino Recipes
  9. From Cappuccino to Caffé Latte
  10. Espresso Cups
  11. Last little bit of trivia
  12. Hope for the Hopeless


Gonna let you down and leave you flat!
Having trouble foaming and heating milk for your espresso beverages? If you’ve got the patience and a few gallons of milk to experiment with, perhaps I can elevate your coffee cuisine to a new height of palatability and open new doors of artistic expression.

Gather ’round all you clowns.
Create lovely hot beverages! Use simple ingredients! Requires simple tools! Here’s a list of the few items you need:

  • A device that produces steam

  • Some way to control the steam output

  • A stainless steel milk pitcher

  • Several clean towels

  • An hour or two of undisturbed study

  • Three or four 8-ounce clear glasses

  • Some food coloring

  • Five or six gallons of milk

  • Optional (but strongly recommended) thermometer

  • Optional (but highly desirable) carton of cream or half ’n’ half

You can heat milk carefully in a microwave or by stirring it constantly in a pan on top of a stove. For efficiency, speed, texture, and taste nothing beats steam heating. And nothing beats an espresso machine for this operation.

Steamed milk definitely tastes better than milk heated any other way. It is sweeter because your tongue reacts instantly to the decreased surface tension. Steaming the milk can be a drudge or one step on your path to culinary glory. It’s serious chemistry, too. In addition to violently and rapidly heating the liquid, steam alters the physical characteristics of milk proteins in a process called denaturing. Changes are taking place on a molecular level in the milk but the results are cosmic. And, of far more interest to you and me, steam-denatured milk can become something quite fascinating — something cold milk simply cannot. Steamed milk can be inflated, built up into a swollen, lofty lattice. That is, it can be turned into an extraordinarily cool thing: foam.

Happiness is a warm gun.
Your steaming vessel needs only enough room for the milk to double in volume and to keep the hot swirling mixture from sloshing up the sides, dripping all over your counter and down the front of your jeans. Almost any sturdy, non-plastic vessel will work. Ceramic and glass containers are heavy, a bit unwieldy, and you don’t want to drop one on the counter. Stainless steel is ideal. I like to use a .75 or 1.0-liter bell-shaped pitcher with a tightly pointed pouring spout.

A valve on the steam system controls the amount of heat transferred to the milk. You do not want to get the milk too hot because denatured milk proteins don’t foam well; they just break down. If they get too hot, the break down completely. The protein strands float to the surface and coagulate into far less fetching stuff: curdled protoplasm.

An instant-read thermometer is handy in any kitchen. Buy one. Thermometers for milk production usually include a small clip that keeps it firmly attached to the pitcher while the milk is being swooshed around.
I’ll tell you about the other items later.

You know how hard it can be.
There are several places where you can learn different ways to foam milk. Your public library may have coffee books by Nick Jurich, Kenneth Davids, Tim Castle, and Corby Kummer. Larger booksellers stock additional titles by David Schomer, Francesco Illy, and the tireless marketing grunts from Starbucks. Seems silly for me to repeat what those worthy experts have to say so I’m just going to give you the 3-step version:

  1. Put the steam tip under the surface of the milk and open the valve.

  2. Slowly lower the pitcher until you get a delicate foaming action.

  3. Stop before you boil the milk.

That’s all there is to it. Foam is fine but you are reading this to help you surpass frivolity, to forgo the merely frothy. You are here to fulfill foam’s fate to become something superior: Microfoam. Yeah, we’ll get to that. But first, some background information.

You don’t look different but you have changed.
Ever wonder why soapy water is almost clear but soapsuds are white? Add a little soap to clear or lightly colored water and when you shake it up, the suds are white. Simple physics; diffraction and reflection of light. Light strikes the bubbles, bounces around, and is dispersed and reflected in all frequencies or colors equally.

The same thing happens with milk. The little globs of fat floating in the milk water reflect light evenly in all colors. So milk appears to be white. Milk with lower fat content tends to appear bluish white.

Sidney Perkowitz, in a fascinating book, Universal Foam: from Cappuccino to the Cosmos, discusses several types of foams, grouping them into two major families: foams formed from emulsions and foams formed from colloids. In all cases, a foam tends to be unlike any of the substances from which it is made.
As espresso fans, we are interested in only two foams: Milk froth and crema. You can read all about crema here, but for foam to form in milk, we need three things:

  1. A substance existing as an emulsion. In this case water and milkfat.

  2. Another substance that acts as a surfactant. In this case milk proteins that have been denatured by steam.

  3. And an introduced gas. In this case bubbles of air.

Your mother should know.
My father made soufflé whenwe had guests for dinner. I was young enough to think the oven was magic. There‘snothing magic about cooking but understanding the chemistry behind the fun foodswe eat might make your milk foaming easier.

Sidney Perkowitz describes several familiar edible foams like raised breads, carbonated beverages, fermented beers, whipped cream, and beaten egg whites. Soufflé and meringue are little more than egg whites and air. Egg whites are the simplest of colloids, merely balls of proteins in water. Bang on them long enough with a wire balloon whisk and the protein chains will denature, loosen, and slip apart. They become a disorganized assortment of separate, sloppy strands. While the balloon whip is beating the proteins into submission it is also drawing air into the mixture forming small bubbles. The strands retain some elasticity and form the surface-acting agent, or surfactant, giving the bubble skins variable surface tension so they resist rupturing. When baked, the skins dry out — they denature completely — and set firmly. In the case of soufflé, expanded steam creates the picturesque puffiness. If the steam escapes or cools, the soufflé implodes. Goo goo g’joob!

Way too much information.
Crema goes so fast. You turn around it’s past. Make no mistake; crema is absolutely crucial to espresso. Crema holds all of the volatile compounds that constitute the breathtaking aroma of espresso. Crema is where your nose gets most of its information about your espresso. If your nose is well informed, your taste buds will gladly come along for the ride. Let us contemplate crema.

Wait, let’s consider espresso first. Brewed espresso is an enigma of physics. It is all at once a solution, a suspension, and an emulsion. Espresso has body, more viscosity than regular coffee, provided by trace amounts of fats and starches. It contains sugars, polysaccharides, acids, caffeine, proteins, lipids, oils, colloidals in suspension, bits of fibrous plant matter, and carbon dioxide. Carbon dioxide? Like soda pop or Champagne?

Coffee beans literally exude carbon dioxide as a byproduct of the roasting process. The burr coffee grinder, when set for espresso, slices beans into flaky grit. The flakes increase the surface area tremendously, rupturing cellular walls and allowing even more carbon dioxide to escape into the atmosphere. When hot water is forced through the finely ground coffee, much of this carbon dioxide is liberated and, because the brewing chamber is pressurized, it dissolves into the water.

In a sense, crema is only a potential; it is nonexistent until the liquid leaves the puck of coffee and dribbles from the portafilter’s spout. In the low-pressure atmosphere outside of the brewing chamber the molecules of dissolved carbon dioxide expand into microscopic bubbles. Think of a bottle of Champagne, a spritzer of carbonated water, or a can of soda pop. The bubbles only appear after the container is opened and the pressure equalizes.

Back to crema: Protein strands, available from the ruptured cellular material and denatured by the hot water, become surfactants and stabilize the tiny bubbles. The polysaccharides and lipids increase the viscosity of the fluid, resisting the pull of gravity and slowing the drainage. As the fluids drain off, the bubbles dry out and when the surfactants can no longer support them the walls collapse. The breaking down continues until the crema foam dries out or disappears completely. Too much information? Okay. Let’s just say crema is a foam of carbon dioxide and espresso.

I wouldn’t mind if I knew what I was missing.
Well, yes, I would. I certainly mind. I’ve been to Vivace in Seattle and I’ve been served caffé latte and cappuccino by baristas who take pride in their ability to create delicious and visually interesting beverages. So, yes, I know what I’m missing and I mind it a great deal, damnit.

When you find yourself in the thick of it.
David Schomer, proprietor of Espresso Vivace, did not invent this velvety smooth mode milk can obtain. In Italy, where espresso is considered the foundation of serious social intercourse — a basic food — this is how milk has been served for decades. Mr. Schomer is convinced, literally haunted by the idea, there is no other way to serve foamed milk.

Why is Schomer a total nutcase over one component of the American specialty coffee scene? I can tell you only that, once you’ve tasted it, you’ll never again voluntarily settle for plain ol’ hot milk. Microfoamed milk is luxuriously textured but it is not what you would call thick. It pours slowly, more like a premium white interior latex paint and less like a yogurt shake. Call it oozy, soupy, or gloopy. Call it mucilaginous, if you absolutely must. What do you say we call it velvet chiffon?

It is shining.
Over-stimulated foam plops from your pitcher in clumps and clods. Stretched too far, the volume becomes unsupportable. It’s too darn loud. The blobs of warty foam ride on top of thin milk. Obviously your assignment has not been successfully completed. What went wrong? Rinse your tools, go to the store, and get another gallon of milk. Lay down all thought, surrender to the void. And start saving for a better espresso machine.

When properly made, things get reflective. The bubbles in the chiffon are virtually microscopic, so fine the surface has sheen, a reflective gleam, and this means it’s supreme, a real boost to your self-esteem. Microfoam is a glossy and gooey foodstuff. Like most foams, it is an innovation; in this case, a new substance that only barely resembles either of the primary components that are simply milk and air.

Getting good microfoam is a two-step process. Step One, The Fattening Phase, in which slurps of air are added to the milk emulsion to stretch the volume and create a basis for the foam. This sounds easier than it really is. You’re trying to create small bubbles — so small you cannot really call them bubbles. You’re trying to end up with fewer visible and more foam. Yet this is far easier than I’m making it out to be. After a few tries, you will realize the introduction of a small amount of air into the milk is done in just a second or two. The trick is to keep the bubbles quite small.

Step Two, The Fusing Phase, in which the foam is further refined and stylized into a gooey chiffon. This is also known as the Whipping Phase because you will be using the full force of the steam wand to violently swirl the air and milk mixture. Your microfoam will last longer if the surfactants have a chance to develop without being completely denatured. You want the milky water to drain slowly from the walls of the bubbles. Once you get the hang of introducing small bubbles of air, the incorporation/fusing/whipping phase is actually more important than the fattening phase. Evenly distributing the air, breaking the bubbles up into yet smaller bubble-ettes, and refining the liquid into a smooth and viscous lattice all take place during this phase. After you’ve stretched it, open the valve and run the steam at full velocity, swirling and homogenizing the foam.

Holding them down, turning them round.
Steaming and foaming milk are not just done with your hands. It can be a whole body kind of thing. You can make a bizarre dance out of it if you enjoy performing and somebody’s watching. Concentrate. You must watch the thermometer. You must be aware of the feel of the pitcher. You must listen to the steam hitting the milk.

Drop the pitcher too fast and large bubbles instantly form like a blob of albino frog eggs. We call those big bubbles “grain.” Trying to recycle grainy bubbles takes some stealth, you’ve must sneak up on them and whoosh them into the steam stream without making more of them. There’s a sweet spot to this and you must find it before the milk boils. It’s easier to start over.

Finding the sweet spot for maximum air injection is not a one-time accomplishment. As the volume of foam increases and the temperature of the milk rises, the pressure of your steam delivery system might diminish and the sweet spot moves in four dimensions. Lusciously fine foam can be accomplished using a technique that Mark Prince calls “dancing with the steam tip.” Constantly on the move, the pitcher is raised and lowered and moved repeatedly from side to side. Depending on the design of the tip of your steam wand you’re also looking for the trajectory that gives the maximum swirling velocity without sucking any more air into the vortex.

If you’re playing along at home, put the thermometer in your pitcher while you work. Try not to surpass 100oF in phase one while stretching the milk. You will have between four and sixty seconds to perform the second incorporation and texturing phase. You want to create an exquisitely gooey mixture before the milk shoots past the 150oF mark. Remember that you will need a few seconds to reach up and shut off the steam so start moving your hand toward the valve when the thermometer starts to approach the 145oF mark.

All my bubbles seemed so far away.
Making ugly bubbles in milk and getting it to puff up is a no brainer. Any minimum wage food service worker can do it. You can probably create typically warty foam, “bubble rubble,” without much effort yourself. Frothing aids make foaming milk even easier by injecting small volumes of air or whirling the milk with miniature turbines. I am not a fan of any such device, mechanical or passive, and you really do not need one to make excellent steam-foamed milk. If you’re new to this foaming thing and you have one of these doodads on your machine, go ahead and use it for a few days then be brave and throw the training wheels away. You can do it.

Money can’t buy me froth.
Even the most expensive, totally automated, dual boiler or heat exchange espresso machines require a certain level of skill and patience to create the kind of foam I’ve been talking about — the microfoam velvet chiffon.

Microfoaming requires your full attention and the little silicon brains in the Super Automatics simply cannot hope to cope. Milk temperature, protein lattice, fat content — heck, what the cows had to eat, and how long since the milk left the cow are completely out of our control. Yet these funky variables must be dealt with in the course of just a few seconds. Steam pressure is variable, too, fluctuating over a wide range on just about any non-commercial espresso machine.

It’s getting better all the time.
Practice will make you better but you cannot achieve perfection unless you’re in the espresso business and you proudly steam four or five gallons of milk every day. Clearly, unless you’re a barista, you will always be chasing after chiffon perfection. Take your time to learn how your machine behaves under various circumstances and be aware of possible dangers that might damage your machine or cause burns from splashing milk or steam. For instance, most single boiler home units can be operated in the steam mode until the boilers are dry. This will totally kill your machine and baby, this kind of abuse is not covered by the warranty. You must learn when to stop and refill the boiler.

You should also know how long it takes to switch between steaming and brewing modes. Most high quality home machines are ready to foam less than one minute after activating the steam function. Going back to brew mode may require repriming the pump or running water through it to cool the system down so your next espresso is not incinerated. RTFM: Read the freakin’ manual that came with your machine. And practice. Go buy another gallon of milk.

Nothing you can do that can’t be done.
Still with me? Want a lesson in obsession? Why did I list food coloring and some clear glasses as Foam Production Education tools? Read on, my fizzy friends.

Find an 8-ounce, old fashioned-style clear glass and put a few drops of blue food coloring in the bottom. Turn to your machine and do your best to get a pitcher full of creamy foam. Pour it into the glass and then look at it from the side. Compare your view with these photos.

Frothed milk with food coloring example Frothed milk with food coloring example Frothed milk with food coloring example Frothed milk with food coloring example

There are three distinct layers in the milk foam presentation. At the bottom, because it’s heaviest, is the hot, milky water. Floating on top is the foam. Between the foam and the water is what I call the interface. Your success is gauged by the subtlety and persistence of the interface.
Because we’re nuts over a low-fat diet, the typical American foam is made of non-fat or one-percent milk. The presentation consists of stiff, white, dry foam riding on top of a layer of blue-colored water. The interface is unmistakable.

Microfoam, however, will show only a single, contiguous layer for ten or more seconds after pouring. Soon, though, the water succumbs to gravity and will begin to drain from the foam. The two layers will become evident and the interface resolves. The interface remains blurry for a few minutes but will eventually become a thin or nonexistent line.

Frothed milk with food coloring example Frothed milk with food coloring example

The starting temperature of your milk, steam pressure, amount of air inclusion, and how long you are able swirl in the fusing phase will make each foam session a new challenge. With experience you will be able to tell which techniques you need to employ at the steam wand that will lead to interesting variations in your presentation. If you try to change too many of the variables with each batch, you will never be able to keep track of your progress.

The summer of 2001 found me in Seattle on business and I hung out at Vivace each morning I was in town. Schomer was beginning his training with two new hires so I just pulled my stool up to the bar and paid very close attention. Here’s what I learned:

  1. You don’t need a valve on the steam wand. The milk expert uses a foot-activated switch to open and close the binary valve.

  2. You don’t need much air. The milk expert starts with the tip under the surface, steps on the valve switch, and lowers the pitcher until the nozzle is exposed. The air is drawn in for only a second or two. That’s all.

  3. The whipping phase is where it all happens or where it all falls apart. No more air is allowed to enter the mixture. The velocity of the swirling milk is quite high.

  4. Latte Art is MUCH more difficult than it looks. The baristas make it look so easy. That’s the sign of a real craftsman.

Life is very short and there’s no time for frothing and foaming.
When I hit the steam button on my Salvatore, I have about nine seconds before the ice cold milk is 100°F. In another eight to twelve seconds or so the pitcher will be too hot to hold. In less time than it takes to watch a commercial for Taster’s Choice Freeze Dried Coffee Crystals and say “Eewwe,” I can bring six fluid ounces of milk to a rolling boil, turning it into coagulated scum. Utter bubble rubble.

After practicing on a gallon of two-percent milk I was easily cranking out grainy foam on my Salvatore and avoiding the boiling point. But I still could not achieve the acme of frothing finesse: Microfoam. So I started to hack the machine.

I’m fixing a hole where the air gets in.
When I replaced my Rancilio Rialto with a Salvatore Basic model, I knew it would come equipped with a proprietary frothing aid. Nonetheless, I was not expecting my cappuccino career to come to a crashing close.

Top-end, semi-professional machines are equipped with either two boilers or a heat exchanger. The mechanical theory is easy enough. Water boils inside the boiler. Steam leaves through a valved outlet at the top of the boiler. A tube leads from the pump through the boiler vessel and to the brewhead. Heat is transferred to the water as it passes through this heat exchanger but the brewing water itself never comes into contact with water in the boiler.

Unlike conventional, single-stage home espresso machines, boiler temperature is not controlled by a thermostat. Instead, the pressure inside the boiler vessel controls electric power to the heating elements. As you might imagine, such a control device is called a pressure-stat. The hotter the steam gets, the higher the pressure inside the vessel and the pressure stat will turn off the heating elements. If the machine sits idle for a few minutes the steam cools, condenses, and the pressure drops. The pressure also drops if the steam is used to foam milk. The stat will fire up the heating elements when the pressure falls below its programmed threshold.

The water level inside the boiler will drop as steam is vented off or, in some cases, as really hot water is drawn off to make tea or mix an Americano. A sensor activates the pump to keep the water at an appropriate level to produce dry steam and to protect the heating elements by keeping them completely submerged.

I knew where the pressure stat was on the Salvatore so I cranked on that sucker until I thought I’d blow the boiler’s safety valve. I still could not generate enough steam pressure to provide any significant swirling and mixing action to fuse my warty foam into chiffon and this was starting to piss me off.

It occurred to me that steam pressure wasn’t the issue. I needed velocity. Speed was definitely lacking at the exit pupil of the steam wand tip. My Rialto had a three-hole tip and enabled me to become quite skilled at microfoam production (if only a rank amateur when in comes to latte art); I assumed that smaller holes would increase the exit velocity of the steam.

A trip to a brass fitting specialty shop where I found a handful of pipe end-caps. I drilled a pair of 1/16-inch holes in one of them and threaded another to accept a Rancilio-style steam tip from my old Rialto.

3 different tips Rancilio Tip

3 Different Tips

Rancilio Tip

When I put these shop made devices on my Salvatore everything changed for the better. The end-cap with the two holes was a terrific advancement over the proprietary device Salvatore supplied with my machine but I still had the impression the holes were a bit too large. Swapping out the two-holer for the Rancilio tip was a revelation. Suddenly, I was back in the microfoam business and serving up exquisitely gooey cappuccino and fluffy latte. It was that easy. Sheesh.

There’s a chance that our foam may fall apart before too long.
Frothing and foaming are fun and frustrating feats. The simple application of water vapor turns a common food item into a delightfully tasty and playful enhancement to your beverage service. Whether you are making hot chocolate, flavored warm milk drinks, or classic espresso beverages, steamed milk tastes better and the mounds of froth will add a touch of class to your presentations.

And our friends are all aboard.
Crema is necessary. Crema defines properly crafted espresso. Crema is one of only two ingredients used to create latte art. Yet crema is elusive, ephemeral. Crema will only last a few moments. If you are entertaining guests and producing many drinks you can almost forget crema as confirmation of your culinary craftsmanship, a characteristic demonstrative of your caffé coolness.
Entertaining is a distinct challenge for the espresso snob who normally satisfies her own jones with a small pump machine. On a single stage home machine, making espresso beverages for more than three people is an athletic event. You might want to borrow a machine from another espresso snob. One for brewing, one for frothing. As long as your kitchen’s electrical supply can support both ten-amp appliances, running two machines will make your pretend espresso cart scary efficient.

And though it’s only a whim.
You can make it with steamed or microwaved milk and top it with froth whipped up in a blender or created in one of those plungers that resemble a press brewer. You can even use a premixed powder of sugar and instant coffee. Squirt it with canned whipped topping. Put a cherry on it. Sprinkle it with chocolate ants and green sugar crystals. You can call almost anything “cappuccino.” Made properly, it is the basis for related drinks. Make the milk first and pour the espresso through the standing foam and you have a macchiato. Keep adding milk and you will sacrifice your cappuccino, progress through the abomination called latteccino, and eventually arrive at the caffé latte.

Tres bien ensemble, these are things that go together well.
Ah, cappuccino. Start with a colloidal foam: effervescent, ephemeral, polyphasic, possibly polymorphic — espresso. Add a buttery-smooth emulsion foam: microfoamed milk. Mingle them and they become something which is neither and yet more than either.

What can be said about cappuccino that has not by those more worthy? Cappuccino is a delightfully delicious, deceptively difficult dainty. Deserving of the effort, cappuccino is tricky but really only requires exact timing and meticulous measurements when you are learning. After you have crafted a couple dozen consummate cappuccino you will be able to crank them out without much effort or thought. A bit of practice and the specifics are soon gauged by eye and by feel.

Testing your cappuccino skills on friends? Keep watching their eyes. Even the most unimaginative cretin cannot help but be impressed by, or at least affected by, cappuccino. A sip of cappuccino — one properly made with ristretto, mounds of crema, and chiffoned milk — is a taste sensation one will not soon forget. The look of surprise on your guest’s face will tell that you have exposed them to one of coffee‘s acmes; you’ve served up sumptuously successful cappuccino. They will remember that burst of flavor and the velvety mouth feel for months. And they will curse you for years. You will have exposed them to a beverage they will not likely ever taste again. This is a very cool way to get even with someone.

Recipes vary around the globe and there is no categorically correct cappuccino. How can this be? Here’s what some of the folks who are paid to write about coffee and espresso have to say about cappuccino:

Nick Jurich (“ Espresso From Bean to Cup”) gives us what is perhaps the most common formula: equal parts of espresso, steamed milk, and foam. Classic Italian cappuccino is described as espresso and frothed milk, nothing else.

Dave Olsen (“Starbucks Passion for Coffee”) initially supports the commonly accepted recipe of espresso, steamed milk, and foam. He then promises Starbucks will gladly serve you a 20-ounce beverage inexplicably called cappuccino. I doubt it contains 6 ounces of espresso so one might presume the formula is likely to be only one tenth espresso, four fifths hot milk, and one tenth stiff, dry and tasteless foam. Put a lid on it, Olsen.

Bernard Mariano and Jill West (“ Espresso Encyclopedia”) give several flavored and Americanized versions along with the common recipe. The authors go out of their way to remind you to preheat everything with hot water from the machine and to use a cup that is large enough to hold the finished beverage. Some interesting variations: A “dry” cappuccino is described as 1/3 espresso and 2/3 frothed milk and no steamed milk; “Michael’s Cappuccino” includes two heaping spoons of lightly whipped egg white mixture to replace the steamed milk, just add espresso and an ounce or two of froth.

Kenneth Davids (“ Coffee: a Guide to Buying, Brewing & Enjoying ” and “Espresso: Ultimate Coffee”) includes the basic thirds recipe with the additional suggestion that you add a bit of sugar. In “Espresso Ultimate Coffee”, Davids describes the texture of the milk foam as the main difference between Italian and American cappuccino. The Italian version is thick and soupy; the American version is dry and airy. Davids devotes two entire pages to colorful descriptions of the perfect cappuccino, the “princess” of espresso drinks, and provides detailed instructions in how to prepare it. Among his preferences are brewing the espresso directly into the serving vessel, frothing up the milk so it’s just soupy, and pouring the milk so the white foam rises to the top, leaving a delightfully elegant golden ring of crema around the edge.

Timothy Castle and Joan Nielsen (“ The Great Coffee Book”) might have used Davids as their primary research source since their descriptions of the “perfect cappuccino” are similar, favoring the golden ring presentation. Castle contributes the observation that, when sipped, the espresso should slide under the foam. He decries the silliness of the “livestock sized” drinks being served in the United States as cappuccino.

Karl Petzke and Sara Slavin (“Espresso Culture and Cuisine”) give us three Italian variations, in Italian, yet. The dry cappuccino favored by Americans is called senza fiuma, without foamed milk. Scuro is dark cappuccino with more espresso and less milk. Chiara is light cappuccino with less espresso and more milk.

David Schomer (“Espresso Coffee Professional Techniques”) digresses radically and calls for a five-to-one ratio of milk to espresso. Including his bar’s signature (but not unique) microfoamed milk, it is served in a 7-ounce bowl. While my personal preference is for his espresso straight, cappuccino and latte are the celebrated beverages at Schomer’s Vivace Espresso bars in Seattle.

Corby Kummer (“The Joy of Coffee”) uses the classic recipe. Corby fills a gap in the literature by providing the reasoning behind serving cappuccino in a nicely rounded, bowl-shaped vessel. It allows one to drink deeply or sip daintily without the foam plopping onto your face or dribbling down your chin.

Through thick and thin, milk will always be my friend.
The Americanized caffé latte, when made with microfoam, will inspire rather than merely entertain. The larger amount of milk will mute the essence of the espresso but the microfoam will penetrate to the taste buds and leave an impression not soon forgotten. You can further enhance the impression by creating a heart- or rose-shaped design in the crema.

The mocha requires a bit more effort. You owe it to yourself and your guests to use the best chocolate you can justifiably acquire. Practice preparing your chocolate because they all behave differently. Some powders are difficult to dissolve while some of the syrups are vile.

Want to impress your friends? Try using a tall clear glass and assemble the ingredients carefully, adding them one at a time, so they settle out as separate layers. I’ll leave the experimentation up to you but the more dense and cooler ingredients will tend to migrate to the bottom.

Take a drink from his special cup.
Elegant china elevates this obsessive espresso silliness to the status of cuisine. Demitasse cups are designed for straight espresso and are about 3 ounces maximum capacity. Cappuccino cups are more likely to hold 5 to 6 ounces. You can also find huge bowls that look like joke coffee cups. Caffé latte looks great in a tall clear glass but I still prefer the bowl-sized cups. Crema decoration is really only possible if your cappuccino and latté are served in mugs, cups, or bowls.

I’ve just seen a face.
Traditionally made Middle Eastern coffee produces a rich foam resembling crema but it is created by boiling rather than by the release of trapped carbon dioxide. This might just be an urban legend, totally apocryphal, but I’ve been told this billowing foam is known as “face.” Isn’t that cool?

Coming on strong all the time, I me mine, I me mine.
Are you a Hopeless Espresso Hound or are you an Insufferable Espresso Snob? I’m worse than either of those. My friends rarely go out for coffee with me. I watch our coffees being made and I provide a running critique, telling them what the barista is doing incorrectly. I may or may not accept our drinks with grace and then I will go to great lengths explaining to my comrades what’s wrong with the beverages and their presentation. We sip and I assure them I can do better at my house. My friends have lost all patience with me. They tell me to get over it, already. Say thank you, shut up, and leave a nice tip.

If you want to develop your espresso brewing and milk frothing proficiencies, think about attending one of the many coffee trade shows. You can buy training video programs and books from several online suppliers including Borders, Barnes & Noble and Amazon. I have gotten the best information and help from Kenneth Davids’ many books and David Schomer’s videos.

Definitions:

Denaturing: Strictly speaking, denaturing means to change the properties of something. Ethanol can be denatured so it becomes highly toxic. Our interest lies in the fact that a biological substance, such as a protein or an enzyme, can be altered from its original or natural state by the application of an external agent such as heat, pressure, radiation, or specific chemicals. Denatured proteins lose their complex three-dimensional structure but rarely lose their function. Enzymes can become inactive, unable to perform their catalytic functions. Proteins that have been completely denatured by heat will precipitate out of a solution or form strong bonds with other available strands of proteins as they cool. For example, boiled milk will coagulate and a scum will form on the surface and boiled egg whites become hard.

Foam: a stabilized froth in a lightweight cellular form usually resulting from the introduction of gas bubbles. Emulsions and colloids are types of foams. Or foams are types of emulsions or colloids. Dunno. See below.

Colloids: Colloids are a type of foam composed of tiny bits of one substance distributed throughout another. Two properties of a colloid that distinguish it from other combinations of substances are the evenness of the dispersion and the difficulty one would have trying to filter the inclusion from the background substance. Examples given in physics books include fog, red-colored glass, various types of smoke, and homogenized milk where the fat globules have been evenly dispersed to the point where they will no longer separate and float to the top to form a layer of cream.

Emulsions: Emulsions are foams in which bubbles of one substance are suspended in another without being mixed together. Milk itself is an emulsion of fat globules suspended in water. Another typical emulsion is mayonnaise in which oils and fats are suspended in egg white and water or wine.

Surfactant: Surface-acting agent. Strictly speaking, a substance capable of reducing the surface tension of a liquid in which it is dissolved. The classic example of a surfactant recognized by many people is a laundry detergent. The surfactant properties of detergent actually allow water to wet the soils, especially oily deposits, making it possible for them to separate from clothing. This isn’t exactly true in our case. A surfactant is needed in milk foam to keep the skins of the bubbles wet and pliable. The surfactant in milk froths is the denatured strands of milk protein.

Surface tension: In the world of physics, this is the tendency of liquids to reduce their exposed surface to the smallest possible area due to molecular cohesion. The surface of a liquid will take on the apparent properties of a membrane because the molecules at the surface tend to pull closer together.

Crema: a fine foam of tiny bubbles of carbon dioxide that floats on top of properly made espresso. Effervescently ephemeral, crema is actually polyphasic, at once an emulsion and a colloid in a foam whose formation shows attributes of both. Crema was once the hallmark of espresso perfetto, the perfect espresso, indicating that all possible variables were correctly controlled by the barista.

Microfoam: Yeah, this is an anachronism invented by David Schomer, as near as I can tell.

Additional information on boiled milk: If you’re a Boomer, your mom or dad probably made hot chocolate or pudding for you by heating milk in a pan on the stove. This was back before the wide availability of instant mixes and the main ingredient was fresh milk. Remember the scum that sometimes formed on the surface? When milk boils, it denatures the proteins totally and they gather together in the only way they can.