What is Scale?


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(Photo: Cory Eldridge.)

[S]cale is the nasty, pale mineral buildup in your espresso machines, batch brewers, and kettles. It’s hard, but chips off in flakes. While harmless and tasteless to your customers, it’s pretty gross and, worse, it can destroy your equipment.

Scale is formed in a boiler by an interaction of calcium and bicarbonate, compounds found in water. When the two combine, they create calcium carbonate, better known as limescale. Limescale can coat the inside of equipment that’s exposed to heat and water. At low concentrations of bicarbonate or calcium, in water we call soft, scale forms very slowly, but at higher concentrations, in hard water, the formation of scale is rapid. Without proper filtration or maintenance, the stuff will clog water lines and destroy valves, and will compromise pressure and temperature gauges.

The rub is, as Chris Hendon points out in his article, we need calcium, bicarbonate, and heat to brew a good cup of coffee, so scale is often inevitable. So buy yourself some descaler and make sure you have regular technician visits scheduled.

Cory Eldridge is Fresh Cup‘s editor.

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