How many times have you made the very same tea as yesterday, in the same amount and with the same brewing time and temperature, but it’s not quite as good – a little flatter, maybe, or less aromatic? You used the same tried and trusty teapot, infuser or tea maker. So, why the difference and disappointment?
Maybe it’s the cup, not the tea. It’s easy to treat all the coffee mugs, tumblers and tea cups you have at home or in the office as pretty much the same. Most tea drinkers don’t know or care exactly what they are made of: ceramic, glass, stoneware, porcelain, plastic, earthenware, melamine, or even polystyrene, and whether it’s glazed or in natural form. They mainly pick their cup for its size, shape and handle. Or they grab whatever is near at hand.
Cups are not so interchangeable. The materials they are made of have a surprising impact on tea taste, especially for an aromatic tea whose flavor offers some complexity, so it’s worth being more selective. The same applies to pots, teamakers and infusers, but in general tea enthusiasts pay a lot of attention to the one(s) they use on a regular basis, whereas they may go through a dozen different cups and mugs in a week or so, casually and even automatically. Choosing a pot gets much more thought: cost, design, ergonomics, size, etc.
If you want to get the best out of the tea you drink, switch your thinking from what style of cup you want to what type of material it should be made of. Very roughly, there are three overlapping elements of the tea experience: (1) the initial aroma and first sip, (2) the “mouthfeel” and full taste in the body of the tea, and (3) the aftertaste and lingering “notes” of the drink. The purpose of the kettle, teapot, infuser and other accessories is to deliver the tea to the cup at the right temperature and the right moment for the chemical compounds to bring out these three qualities.
The cup can affect any of them, often dampening out what should be part of the overall pleasure. Everyday instances are the porous clay in a standard coffee mug trapping some of the initial boost of aroma, the tea cooling too quickly and losing zip, or a hint of a plastic taste in the fresh-made brew. Less frequent or even indiscernible impacts are lead and cadmium leaching from the hard glaze added to the inside surface of the cup to make it less porous, and stored up water droplets blowing up the cup in the microwave. (Yes, it does happen.)
What does a cup need to bring out the best in your tea?
- Be nonporous so that it does not interfere with the unfolding of the aromas and flavors; the material should be neutral and not “leach” – transfer molecules from the cup – or leave traces of the tea’s compounds trapped in its tiny pockets of space.
- Modulate the heat of the tea to meet your preferences: keep it hot and cool it down quickly or slowly. A cup that is broad at the top cools tea more quickly than a tall, narrow one, which however concentrates the aroma. This is comparable to the different shape of glasses for red and white wine glasses. Ceramic cups tend to retain heat longer than glass ones. Thinner cups transfer heat faster.
- Be safe chemically, in dishwashers and microwaves and inert, with minimal interaction between the material and the tea. Borosilicate glass is excellent in this regard, but the very fact that it is highlighted in ads as “BPA-free” indicates that BPA-loaded is definitely not good. The same applies to dishwasher safe; the term warns you that there are plenty of unsafes around. (Bisphenol A is used to harden plastics and is banned for many applications.)
The main choices
Tea cups are made out of three main types of material: ceramics, glass and plastic, with cast iron occasionally used. These provide for a near-countless variety of shapes, sizes, decorations and features, along with differences in specific chemical compositions that affect heat transfer and porosity. They all offer wonderful designs, so you don’t have to give up appearance and style for function, or the reverse.
You could collect teaware by buying something new every day of your life and never exhaust the range of English-style dainty cups and saucers, Chinese porcelain, metal/glass combinations traditional in Turkish and Russian tea cultures, and tiny Japanese ones designed for ceremonies and special tastings. There are so many: Yunomi, Arita Gosho, Stafford, Winged Grace, broken loop, footed, moustache, zarf, zhong, podstakannik, kumidashi chawan…
But don’t let the varied styles divert you from the core aspect of any cup’s composition: how porous is it? For general use, the less porous the better. Increasingly, too, the tougher the better; cups get a lot of handling and hard treatment, especially travel mugs and tumblers. Obviously, safety is a common sense priority; here, the basic message is avoid plastics, beware of the dishwasher, and never open the microwave door.
- Forget the plastics as a conscious choice. There really is no positive feature beyond their being light, cheap and unlikely to break. They are, though, chemically active, with some low probability but high nastiness potential impacts. They are so commonplace that they are hard to avoid; it’s worth having some information about them. If the examples provided here scare you: good.
- Porcelain has been the material of global choice since around 1300, in China, and from the 1800s in Europe. (Chinese variants were being made as early as the 6th century.) It is thin, translucent and fairly fragile.
- Borosilicate glass or what we know by its trademark name Pyrex is very tough and handles heat well. The thermal insulation tiles on the Space Shuttles were coated with it.
Sip and Savor or Glug and Go?
The main distinction between porcelain and borosilicate glass is a slight difference in heat retention and a big one in the thickness of the lip of the cup that you drink from. (This is a byproduct of porosity that affects manufacturing.) This does have a subtle impact on teas, which may be summarized as SS for porcelain – Sit and Sip – and GG for glass – Glug and Go. The thinner the lip, the more you naturally let the tea glide onto your tongue. That’s why a porcelain or bone china cup seems so refined. It encourages you to sit and savor the flavor of the tea.
The thick material of glass and stoneware retains the heat well but it creates an autonomic reflex to take a big gulp of the tea. This is fine for big flavor brews, especially the breakfast ones that you rely on to transform you from narcoleptic zombie to functioning humanoid. But if you are trying out a range of mid-price teas, where you want to enjoy their individual lightness, aroma or aftertaste, choose the cup that helps you sit and sip. You’ll be better able to sense the differences. The obvious best option is both/and not either/or: an SS porcelain cup for use at home and a GG glass doublewall (a tumbler with built-in infuser) for travel and the office.
Porosity? Like Swiss cheese?
The main source of differences in how cups affect tea is the porosity of the material: how much it is like Swiss cheese, with pinholes where air and water can penetrate it or pockets of empty space be formed by small mixed in extra bits and pieces, such as mineral particles in the rock clays that are the base for ceramics.
Porosity is measured in terms of the void-space fraction and is generally proportionate to the hydraulic conductivity, taking into account pore throat radii. Vuggy porosity is of particular relevance to geological poromechanics, though not to Earl Grey consumption.
Think of the poured hot liquid on the larger scale as a tidal flow. The cup is like a sea wall. If it’s pitted with small holes and lumpy impurities, water gets trapped and that absorbs and dissipates the odors of the salt and seaweed. If it’s marble-smooth, all these stay within the liquid as it flows. At a more microscopic level than sea waves cresting and crashing, the interaction between the inner surface of the cup and the brewed tea has a surprising impact, one that you may not directly taste but it’s there as an awareness of something missing. It’s flat and loses some of its “notes” and overtones.
Ceramics vary widely in porosity. The term technically means made of clay that is fired in kilns, but it is loosely used to refer to stoneware – “pottery” – earthenware, porcelain or terra cotta or just some of the above. The clay and firing heat determine a ceramic’s type. Clay is fine-grained natural rock or soil material with minerals and traces of metal oxides and organic matter.
There are many classes of clay. For cups, the main categories are:
Earthenware, the most common and easiest to work with, hardens at a firing temperature of 950-1100 centigrade. These are the big, intendedly clunky, pottery mugs. They are very porous and rough, chalky and grainy in surface. They are generally not glazed, which is the addition of a vitreous – glass-like – coating that eliminates porosity and adds color and design. To retain heat, they are made thick in their walls.
Stoneware: 1160-1300 degrees, impermeable, dense and hard. There is a wide range of clay quality in terms of size of particles, impurities and non-clay elements such as mica and quartz. Stoneware may be fired once or twice, to facilitate glazing. It is heavy and thick and widely used for coffee mugs. It is inexpensive to make. It retains heat well but that means that it can crack when subjected to extremes of temperature.
This is cheap everyday functional drinkware and there is often corner-cutting in production to keep costs low. For instance, glazes may not join well to the clay and crack, forming “crazy” spider web-like patterns. When this happens, throw the cup away. Immediately. The cracks can provide nesting hideaways for bacteria. Never use a dishwasher no matter what the manufacturer states about this being safe; stoneware is rigid and intolerant of heat changes.
All in all, stoneware is acceptable but not outstanding on any dimension of cup features, including variety of shape. Most tea cups and coffee mugs are uniformly cylindrical, with the bottom and lip being pretty much the same radius. Its structural characteristics mean that they are invariably thick-lipped Glug and Go. Porcelain cups typically are narrow at the bottom and widen out at the top; this enables a better balance between heat retention and expansion of the aroma of the tea.
A small but definite concern about stoneware in particular and ceramics in general is that many of the most popular and bright glazes get their brightness and color from lead and cadmium oxide. This passing comment by an expert is a little disconcerting: “The toxicology of ceramic materials is often underestimated and sometimes neglected in our ceramics institutions.” He describes the consequences of cadmium exposure as gruesome and, it seems, not infrequent.
Another analysis states that “there are some glazes that contain lead and cadmium and still say that they are dinnerware safe…” and “a small amount of leaching is allowed by law.” It makes the point that no one can know what will happen to a glaze after years of the cup being used, run through the dishwasher thirty or more times, the glazes having “crazed”, and they have been microwaved who knows when. “Some potters say that you should never use these ingredients for dinnerware. Never, period.”
Porcelain: typically fired at 2300 degrees but this may be reduced to 1900 by adding unusual ingredients. Uses clay with very fine particles, mainly kaolin, also known as china clay. This is hard to work with because it lacks the plasticity and malleability of the clays used in earthenware and stoneware. Cracks and deforms easily in firing since the ideal density is achieved very close to the melting point.
The result is a thin, almost translucent, delicate and smooth cup. It doesn’t need glazing to ensure nonporosity, though light glazes are often added for decoration. Variants use “hard paste” clay mixed with feldspar, kaolin and quartz and marks German Meissen porcelain. Soft paste adds soapstone, lime and what is termed “frit” mixtures of enamels. minerals and other clays. It was the breakthrough development in matching Chinese porcelain and produces a more granular and shiny white body than hard paste, with the advantage of lower firing requirements. French Sevre china is a noted example.
Bone china is technically different from porcelain and fine china, but has the same charcharacteristics. It is more fragile but cheaper to make. It adds bone ash to the clay. That comes from cow bones, which can be a creepy idea for many people. It was invented by Spode and became the dominant material used in English teaware.
Porcelain and bone china are terrific choices for cups, except for their fragility. They look good, are a pleasure to handle and keep tea warm. They do not interfere with the flavor or leach. Porcelain remains the choice of professional tea tasters. It has historically been accompanied by the saucer, and that remains the case for the traditional tea set, which has smaller cups that are narrow at the bottom and widen out to the top. High tea ceremonies invariably include saucers. Tea drinking as everyday routine doesn’t need them.
Glass is a classic material for both teapots and cups. It is nonporous and very smooth. It is commonpalce in Russia, Turkey and Morocco, using standard breakable glass made out of lime soda. The Russian podstakannik is typical: this is an ornate metal basket into which the tea glass fits and is protected.
The more popular, practical and portable option is tough borosilicate glass. This adds boric oxide to the standard silicate ingredients, making it resistant to extreme temperatures and chemical corrosion. If it breaks, it doesn’t shatter into pieces but cracks, snaps and collapses. It’s more expensive to make than lime-soda glass, which is widely used in kitchenware, including glasses for cold drinks.
Tea cups that use the glass are increasingly double-walled: a cup within a cup, separated by a wall of air. The outer and inner pieces are blown separately, dried and firmed up, and then joined together. The inner one keeps the tea hot while the outer one ensures the cup is cool to the touch. One of the special extras is that the transparency of the glass shows both the color of the liquor and the unfolding of the leaf. It is striking and appealing to watch a flowering blossom tea open up its tied ball of leaves inside which is a marigold, jasmine or other flower or to see a teaspoon of rolled oolong expand to half the cup.
Glass does not require glazing and is easy to keep clean, with no need to use the dishwasher.
There’s not much to add about borosilicate. It is an excellent choice for everyday use, equal to but less fragile than porcelain. Your really can’t go wrong in picking it.
Plastics are lightweight, tough, inexpensive and brightly colored. They meet many purposes. Tea making is not one of them. The core problem is leaching. Silicates and clays are chemically inert. Plastics are formed of chains of polymers that vary in malleability, stability, reaction with other molecules and biodegradation.
Rather than review the options in detail, here are a few comments on individual types of plastic that add up to “Keep away.” Yes, they are almost entirely safe, but…
Melamine is nice looking and cheap. It’s the bright plastic dinnerware that usually comes in vivid single colors. It’s a tempting buy. Please don’t go near it. It’s probably safe but reading the details of its chemistry and record of scandals in manufacturing and use across many types of product is a scary exercise. It is not exactly encouraging to know that the melamine is created from urea, dicyandiamide or hydrogen cyanide and the plastic resin is made by adding urea and formaldehyde. Excessive heat can decompose this back to the original elements, “several of which are highly toxic.” This is why you should never put a melamine cup in the dishwasher or microwave. Did you know that? Would you recognize melamine?
BPA, bisphenol A, is a chemical that hardens plastics. It mimics the estrogen hormone. Tests of baby bottles, sippy cups and plastic storage containers not only show that BPA is a decided health hazard (The FDA declared it safe in 2008, a concern in 2010 and banned it from children’s products in 2012) but that BPA-free alternatives are often worse in leaching chemicals. One of the major advertising highlights for borosilicate glass is that it is BPA-free. The main BPA risks include possible though not fully proven impacts on fertility, cardiovascular damage, endocrine disruption, impaired brain development and chromosomes. Again, did you know this? Would you recognize a non-BPA versus BPA-based cup?
Polystyrene foam cups, officially classified as “probably carcinogenic” by the State of California. Proven to lose a little weight when used for hot drinks. That weight goes somewhere: inside you. A striking test is to add lemon to the tea in a Styrofoam cup. It melts quite nicely.
Reusable paper cups are coated inside with paraffin wax and polyethylene plastic coatings and the lid is invariably plastic. This leaches into the liquid. It is a common source of gastrointestinal problems.
There is a simple rule offered by a physician for his patients who are mothers worried about the ubiquitous pre-ban use of BPA in baby bottles: “Use glass.” For tea cups, this can be modified to “If it doesn’t say BPA-free, do not buy it.”
Drinking your tea at the right temperature
How the cup handles heat is one of the last but very important criteria in picking the best type of cup for yourself. You sometimes want the tea to cool quickly or stay hot, depending on the situation. You also would prefer that the one piece of tea ware that you put in the dishwasher emerges as still one piece and is not cracked, smushed or melted.
Here’s a quick historical footnote about keeping tea hot. The traditional English tea cup was designed to serve black tea very hot but the thin porcelain surface and wide brim that brought out its full aromatic flavors meant that it cooled fast. This characteristic led to one of the most epochal and seismic innovations in the history of tea, and the first that marked an advance on Chinese practice. It is an instructive moral on just how important it is for you to get the heat/cooling right. Its consequences reverberate across the social structures of society. This is, of course, the tip.
Today, tips are the gratuity, service charge, small change or “extra” that you expect to pay after you get the bill in a restaurant or get out of a cab. It originated in the new tea gardens of London that sprang up in the late 18th century. These were the outdoor attractions where families could stroll, groups of non-male chaperoned women were welcome, and tea was brought to you at the table.
It became the custom to provide a wooden box marked T.I.P.S. – “To Ensure Prompt Service.” Slip a coin in the slot as you were seated and the waiter would speed up the arrival of your steaming hot tea from the tucked away kitchen. This prepayment for service became extended across every area of everyday life. And it all began in order to make sure the tea arrived hot.
Illustration by Tasneem Amiruddin