Double Wall vs The Rest

BH Unlimited Update, Dec 5th 2021.

To make a great pour-over, you have to have stable equipment. A while back we compared the virtues of plastic, glass, steel, and ceramic filter cones. The resounding winner for the lowest heat capacity and the lowest thermal conductivity was, of course, plastic. But, folks, we have a new winner. It’s better than plastic, and it smoked ceramic. Head here for the big picture (free to read) with lots of eye-opening temperature profiles; but here follows a few stand-out findings from our most recent experiment.


The Experiment

Double wall glass designs have been on the market for some years, but a new design by Brewista takes the idea a step further by creating a fully-sealed double wall filter cone. The Tornado is very similar in shape and size to a Hario V60 02, so we set up a comparison between the Tornado and the classic V60, in porcelain and plastic.

To find out how much heat each cone pulls out of the water, we set up a thermocouple with the probe in the middle of the exit hole of the brewer. We sealed the base of the cone to prevent water flowing out, poured in 200 ml of water at 90°C, and recorded how the temperature changed over time.

Temperature changes in the three types of filter cones over time. The reading at time 0 is the temperature of the water immediately before pouring it into the cone.

It was immediately clear that the porcelain was pulling a lot of heat out of the brewing water. By the time of the first measurement 30 seconds in, the water temperature had dropped a whopping 20 degrees. The plastic brewer, meanwhile, was absorbing a lot less heat, which is what we would expect to see, as plastic is about 20 times less conductive than porcelain . The surprise, however, was that the double-walled glass brewer was doing even better — despite the fact that glass is more conductive, and has a higher heat capacity, the extra insulation provided by the air gap between the double wall prevented heat from escaping the brewing water right from the very start of the brew.

But what about temperature profiling?
If you’ve been inspired to try a bit of temperature profiling with your pour-overs after reading about the recent World Brewers Cup, then you’ll be pleased to hear that, at least in theory, insulation is better for temp profiling: You're minimising the effective thermal mass by isolating it from the slurry. Unless you actively want to lose heat without using different temperature water (i.e. you’d prefer not to have to buy two PID-controlled pouring kettles). But that's not exactly profiling, more like choosing a different (fixed) profile based on your material choice. Something we’ll explore more on our next outing … to the boundaries of coffee 😀


TEM

The Espresso Machine online course has officially become a certification course this week. The final assessment was published this morning, Melbourne time. BH Unlimited subscribers can head in there at your leisure and bag a new certification. Plus, we left this new quiz at the end of Chapter 4 open access to give any folks without an active subscription a chance to test out their knowledge of the history, form, and function of the espresso machine. FYI, Chapter Five’s quiz addresses the modern era, where flow profiling and boilerless technology have become a reality.


BH Tools

Our Hong Kong and North American warehouses are in stock for the holiday season with cupping bowls, tampers, and pitchers. Visit Barista Hustle Tools .


Coming Soon

Following on from many recent requests, we’re delighted to say we just started plotting out a new Roasting Science course and certification. The first instalments should be out just in time for Christmas.


The Coffee Buyer’s Guide to Brazil

When you picture a Brazilian coffee farm, you most likely imagine rows of coffee plants stretching across the Cerrado, in one of Brazil's largely industrialised farms. And yet, the majority of Brazilian coffee is produced by smallholders. This week in the Coffee Buyer’s Guide , we visit two small farms in Brazil to learn about how they harvest and process their coffee, and how they adapt to compete with large scale agriculture.

Cafezal em Flor is a specialty coffee farm in São Paulo that has built a sustainable business by diversifying into agrotourism. Despite their small size, they are able to use mechanisation, and have adopted the latest processing methods, such as controlled fermentation with cachaça yeasts, to get the most out of their coffee.

Sítio Vargem Grande , high in the mountains of Caparáo, has excellent terroir for growing coffee, but the prolonged rainy season means that their coffee cherries ripen at different times. They have adapted to this by selectively handpicking all their coffee — a rarity in Brazil — and focusing exclusively on very high quality production.


Our Editorial Policy

At BH we never do ads for products on our website. There’s no product placement in any of our courses, newsletters or blog posts. Our only income comes from what you pay for your subscriptions. When you see machinery or coffee gear mentioned in any of our educational material, or featured in our course videos, we have chosen to use that equipment because we like using it or because it shows you something you need to see. It’s as simple as that.


The Espresso Machine

History, Form, and Function
EM 4.12 • Recap and Glossary
EM 4.13 • Comprehension Test — Chapter 4
EM 5.01 • Final Assessment


The Coffee Buyer’s Guide to Brazil

Growing, Harvesting, and Processing
CBGB 5.05 • Harvesting and Processing on Small Farms — Cafezal em Flor
CBGB 5.06 • Harvesting and Processing on Small Farms — Sítio Vargem Grande


As always, we're just an email away if you have any queries! Have great weeks and we look forward to seeing you next time.



To the Boundaries of Coffee,
Team BH

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