====== Espresso notes ======

These are a loose collection of notes about espresso brewing.

===== Water treatment =====

Water hardness is a function of two main components: calcium and magnesium. Hardness is typically measured in mg/L of equivalent calcium carbonate, which is found by adding together the concentration of calcium and magnesium ions with multipliers of 2.5 and 4.1, respectively. The formula is [[https://www.lenntech.com/ro/water-hardness.htm|here]]. Typically, magnesium is only a small component, the dominant component to water hardness is calcium. The total is often called GH (general hardness). 

Here is a scale of water hardness (from [[https://www.dwi.gov.uk/consumers/learn-more-about-your-water/water-hardness-hard-water/|here]].

| | Water hardness (in mg/L of CaCO3) | 
| Soft | up to 100 |
| 100-150 | Slightly hard | 
| 150-200 | Moderately hard | 
| 200-300 | Hard | 
| 300+ | Very hard | 

Here are some data points of comparison. 

  * My area of Bath has water hardness of 300 mg/L ([[https://www.wessexwater.co.uk/your-water/|source]]

{{ ::coffee:wessexhardness.png?direct |}}

  * Back in my hometown, Ottawa, Canada, the hardness is 30 mg/L ([[https://ottawa.ca/en/living-ottawa/drinking-water-stormwater-and-wastewater/drinking-water/drinking-water-frequently-asked-questions|source]])

  * A recommended 'boiler-safe' water is Tesco Ashbeck, which has about 35-50mg/L hardness, dependent on the formula. One source is [[https://coffeetime.freeflarum.com/d/619-testing-gh-and-kh-of-tesco-ashbeck-and-volvic-bottled-water|here]]  and another is [[https://coffeeequipmentreviews.wordpress.com/2019/07/22/hard-water-kills-your-coffee-machine/|here]]. Current estimates are 11mg calcium and 3mg magnesium and that comes out to around 40 mg/L hardness.

Here are two clear sources:
  * [[https://www.jameshoffmann.co.uk/weird-coffee-science/water-for-coffee-resources|James Hoffman overview]]
  * [[https://coffeeequipmentreviews.wordpress.com/2019/07/22/hard-water-kills-your-coffee-machine/|Hard water kills your coffee machine]]