In Defense of Porcelain

Why the much-maligned material is perfect for coffee

“When are you making a plastic version?”

Ever since Etkin— the company I cofounded — launched its first product, I’ve heard this request at trade shows and industry events. There’s a vocal group of coffee pros and home baristas who think that plastic is the optimal material for a coffee brewer.

Some appeal to plastic as a cheaper, lighter, or more durable material. I’m sympathetic: one only needs to compare the plastic and porcelain versions of various pour-over drippers to see that the plastic one is often half the price of ceramic or metal ones. Specialty coffee gear is expensive, and I commend anyone trying to make the best cup of coffee in the most economical manner possible.

But the primary reason I’m asked about plastic is performance. There’s a significant community of plastic apologists who are convinced that it offers superior heat retention, which results in a better brew.

I disagree.

There’s a lot that could be said about the unknown dangers of microplastics or the uncomfortably low melting temperatures of many of the plastics used for pour-over brewers or autodrip baskets. But my preference for porcelain actually has nothing to do with my distaste for plastic as a material.

I like brewing coffee with porcelain pour-over drippers because I think it makes the best cup of coffee. The fact that porcelain is an aesthetically beautiful, environmentally responsible, and food-safe material is the icing on the cake.

But before the temperature nerds come at me with TRITAN plastic pitchforks, let me explain.

What is Porcelain?

Porcelain was invented in China. The modern standards of porcelain first appeared around the eighth century AD. Humans have been making ceramics for at least 20,000 years, but the Chinese discovered that the addition of minerals like kaolinite allowed for the ceramics to be fired at higher temperatures, creating a harder, more durable material. The secret is a chemical reaction called vitrification, in which some of the minerals are turned into glass. This makes the porcelain impervious to water, unlike lower grades of ceramic, like stoneware, which have to be glazed.

Like other grades of ceramics, however, the material traps some air in the clay. This serves to make the material less conductive, with the air acting as a sort of insulation. As a result, porcelain conducts less heat than metal or glass, but still has the strength and durability that stoneware lacks.

In other words, it’s the best of both worlds.

Temperature stability

No doubt, many readers are now asking: “But I thought porcelain has less thermal stability?”

Certainly, an initial temperature sink occurs when almost boiling water comes in contact with room-temperature porcelain. Plastic-dripper advocate Jonathan Gagne explains in his excellent book The Physics of Filter Coffee, ceramics (he does not differentiate between ceramic and porcelain) have a higher thermal mass than other materials, and thus can absorb more energy. Gagne concludes that a ceramic coffee dripper is stealing energy from the slurry and inhibiting extraction.

But Gagne’s own tests reveal that a preheated porcelain V60 cools down more slowly than a plastic or metal version. In other words, after the ceramic version has reached a certain temperature, it will stay at that temperature for longer because it has more heat capacity and is less conductive.

More importantly, it’s worth asking: what is the purpose of temperature stability? Is it even desirable? The brewing method that maintains the most stable slurry temperature is the siphon brewer, and yet I know few coffee professionals who prefer it to the flavor profile of pour-over coffee. I think there’s a good reason for that.

As Chemistry professor Michelle Francl explains in her book Steeped: the Chemistry of Tea, temperature during brewing— be it coffee or tea — can be understood as energy. For the water-soluble compounds in roasted coffee to extract in water, the molecules need to be moving around, forming new bonds. The more energy (temperature), the faster this process takes place.

Anyone who has ever washed dishes knows experientially that hot water is a more effective solvent. The higher the temperature of the water, the more effective the extraction. This is why the SCA recommends a water temperature of 195-205° F / 90-96° C. Above this window, you’re more likely to dissolve the heavier, more astringent compounds. Below, the brew is likely to be vegetal and sour.

In other words, the purpose of water temperature when brewing coffee is to achieve a target extraction percentage. If you hit your target extraction, you have enough energy.

But as anyone who owns a refractometer already knows, TDS doesn’t tell you everything. The flavor profile can be modulated by a variety of factors, and this is where I believe porcelain shines as a material.

Early in the brew, the compounds with less molecular mass, such as organic acids, will dissolve quickly. As the extraction continues, the more complex compounds begin to dissolve, many of which taste astringent and bitter.

In other words, a slowly tapering slurry temperature can help mitigate astringency in the cup. (I typically approach turbulence in a similar manner: best applied earlier in the brew if necessary.)

Conclusion

If you’re chasing higher extractions for the sake of higher extractions, I’m unlikely to convince you to recycle your plastic dripper. If you’re looking for sweetness and clarity, however, it’s hard to improve upon one of the oldest materials we have for coffee brewers: porcelain.