Why do espresso shots run faster when I use super fresh coffee? It is a truth universally acknowledged that the gases trapped in fresh coffee create bubbles in espresso, which slows down the flow and reduces extraction. This explains why shots from older coffee run...

Apart from bicarb and epsom salts... A few months ago we released an updated version of our water recipes designed to allow you to easily target any hardness and alkalinity level you want, using two simple solutions — without having to do any complex maths. Since...

Does this mean it’s underdeveloped? Anyone who’s cupped very light roasted coffee, whether from a Nordic-style roaster, or perhaps from a sample roast, will have experienced this: it sometimes doesn’t form a crust in a cupping. When this happens on the cupping table,...

In natural processing, do sugars travel from the mucilage into the bean? Natural processed coffees are typically sweeter and more full-bodied than washed coffees, and often have distinctive fruity flavours. It seems intuitive that the sweetness, body, and...

In our latest poll on the BH Facebook Group, you asked us to check this out: 'If flow goes in much faster than it comes out, then you have the potential to create a fluidised bed. Where does that leave espresso?' Here's what we found out ... This question follows on...

What's the most temperature-stable material to use when brewing? The short answer is: plastic cones are best. They absorb heat from the brew water less quickly, absorb less heat overall, and lose that heat to the air more slowly. To really understand why plastic is...

Is it better to have as many holes as possible in your spray head, hardly any to make more agitation, or somewhere in between? To achieve even extraction in batch brewing, it’s important to get all the grounds evenly wetted — meaning exposed to the same amount of...

A couple of years ago, we published a method for making your own water recipes, using concentrated mineral solutions, diluted with deionised water, to make a range of waters with different hardness and alkalinity. This post updates this, with new recipes that allow you to easily target a specific GH and KH in your water.

"Professor Abbott told us he doesn’t really believe channelling occurs in espresso (except in drastic cases). So if not channelling, then what?" Only a few weeks ago we were telling you that over-extraction isn’t really a thing, and that it’s all caused by...

You asked us to look into this topic, “In espresso, fines migration may not be as much of a thing as we thought.” Here’s what we found.  Fines are the smallest particles created when you grind coffee. Depending on who you’re talking to, they might be defined as any...

Or is it better just to leave them in, when brewing filter coffee? Back in 2012, our very own Matt Perger won the World Brewers Cup, using a 250μm sieve to remove fines. This created a more even extraction, which allowed him to extract higher without getting dry and...

Above and below the coffee bed This week, Scott Rao made espresso with filter papers above and below the coffee bed yielding over 25%. What's he playing at? If you follow Scott Rao’s series of daily coffee tips on Instagram, you’ll have seen one recent post where he...

Decades of trial and error have shown that most people prefer espresso extracted between 85-95°C (A Illy and R Viana, 1995). For lighter roasted, special coffee, the range typically used is rather narrower – 90-95°C. Within that small range though, there are still considerable variations in flavor to explore.

A science professor told BH that with espresso, “in technical terms you have Forchheimer flows instead of good old Darcy flows”. What’s that? Keen readers of this series will remember Darcy’s Law from our discussion of bed depth in espresso. Darcy’s Law is an equation...

In our bi-weekly poll on the BH Facebook-group you asked us, "Can you please summarise Cafe Imports’ Water Activity Paper?", which is based on years of cupping and data logging by the influential green coffee importers. And we said, "Yes we can." Here is this week's...

Dose is one of the fundamental variables of any brew recipe, yet probably the one that is most often overlooked. Most of us probably tweak the grind size or yield very regularly, but always use the same dose. In fairness, this is often for a good reason — it makes...

Any time you’re reading about chemistry, you’re going to come across chemical formulae and equations. You might well remember these from high school chemistry, but if it feels like a distant memory then this refresher might be useful. This post goes out to the BH Unlimited subscribers attempting the first instalment of The Water Course.

The Maillard ‘reaction’ is actually a whole series of chemical reactions that are crucial to creating the characteristic flavours and brown colour of roasted coffee and many other foods – including chocolate, toast, and grilled steak. The reactions are named after Louis Camille Maillard, a French doctor who first described them in 1910.

What is the difference (if any) between a mineral salt, a dissolved mineral, and a mineral ion? A salt, in chemistry, refers to any ionic compound (IUPAC, 1990). For example, table salt, sodium chloride, is an ionic compound composed of sodium (Na+) and chloride (Cl-)...

Geisha, or Gesha, is a highly prized variety, with a distinctive jasmine aroma, and bright fruity acidity. These distinctive characteristics mean it has dominated coffee competitions, and become infamously expensive as a result. Geisha beans are often quite large and...