The matter of static causing clumping while grinding beans has been discussed recently in the Forum.

An article in the Daily Telegraph today (7/12/23) sheds more light on this. I have copied it below. Maybe a light water spray isn’t such a bad idea after all. I have achieved similar results with a small deioniser (see also Dave’s posts on this) but it seems that a water spray might improve the degree of extraction in a way that deionising won’t.

Secret ingredient for better coffee revealedBy Joe Pinkstone SCIENCE CORRESPONDENT

The Daily Telegraph 07 Dec 2023

SPLASHING water on to coffee beans before grinding could be the secret to making the perfect cup of coffee, a study has found.

It is a common technique favoured by baristas hoping to keep their station tidy, as the water creates less mess.

Now, a study from Oregon University which drew on the science of volcanic activity has found spraying water on beans before putting them in the grinder reduces the amount of static electricity on the particles as they pass through the machine.

This not only reduces clumping and makes clean-up easier, but it also creates a finer dust which increases surface area and therefore allows for more flavour to be extracted from the beans.

Dr Christopher Hendon, associate professor of chemistry at the University of Oregon, set up a coffee lab on his campus two years ago and volcanologist Dr Josh Méndez Harper was a regular visitor. Dr Méndez Harper’s expertise in the movement of molten rock, geological activity and rising magma meant he knew that when ash and rocks spewed out of a volcano they rubbed together and create static, which can result in lightning strikes.

“It is similar to grinding coffee, where you’re taking these beans and reducing them to fine powder,” he said.

The pair investigated if the process of spraying water on to the beans before grinding can stop the static forming. They found the technique was effective at stopping charge building up and improved flavour and the strength of an espresso.

“Because the static doesn’t form, the particles also do not clump. Clumps pose problems during extraction because less surface area is available for water contact,” Dr Hendon said, adding: “By having more available surface, you end up with less wasted but extractable mass left in the coffee particles after brewing.

“As a result, by grinding with a small amount of water, you end up accessing something like 5 to 15 per cent more soluble material.”

If everyone in Europe sprayed water on their beans when making a cup of coffee it could stop product worth £200 million being wasted every year, Dr Hendon said. However, the team warned that while grinding and spraying can boost flavour, the benefits will not be realised without careful calibration of a machine to exploit the finer grind.

The study is published in Matter.

To make a perfect cup of coffee, learn from the volcano. So say a group of volcanologists. No doubt they see everything through magmatinted spectacles. But static electricity does seem to be a thing that an erupting volcano and a coffee grinder have in common. Particles in a volcano’s smoke plume rub against each other, sometimes producing lightning from the electricity generated. Coffee grinders similarly create static, making the grounds stick together and flavour the brew less. The answer is to splash a little water on the beans first to discharge the static. A flaw in the scientists’ advice is that the majority of coffee drinkers in British homes do not grind beans. They make coffee from instant powder, ground coffee or those expensive capsules. For the best Eyjafjallajökull effect, they’ll have to be converted to beans.

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