Coffee with bottled water

Project history

  1. old posting: 'roast only' on the Bonaverde - Aldo Parducci
  2. current posting
  3. next posting: 'roast only' on the Bonaverde - Familia Alfaro


Up to now I have used tap water with a filter for my coffee experiments.
According to the water plant the water should be very hard but be only slightly above Ph neutral.
I always had the issue of always having an acidic taste.
Some coffee cups had a very balanced acidic taste, some where so strong as to be undinkable.
Especially freshly roasted coffe that was not given any time to release trapped CO2.


Now I experimented with using cheap bottled water insted.
Absolutely no sour taste anymore. Roasted the day before and even freshly roasted (with all the CO2 still in there and ALYWAYS tasting distinctly sour before) it tasted like a good cup of coffee.

Sadly it contains 500mg Ca/l+64mg Mg/l=>84,86dH and thus will just about kill the machine with scale if used often.


 Let's have a look...
The bottled water was from REWE "Aqua Mia Still" from the Alwa Spring in Sersheim.

There is a nice comparison of German bottled waters here. It has pH values (the content only lets you calculate hardness)


The water plant says, we have 23.1mg/l.
The bottled water says, we have 29.0mg/l
0mg/l is perfect
effect: in high temperature/pressure this creates hydroloric acid thatg eats away on metal.
There is nothing I can do anything about this except maybe carbon filtration.
But I don't care enough about this minor effect to do that.


The water plant says, we have 7.57pH.
The bottled water says: nothing
Water #2 says: nothing

7.0pH is perfect,
6.5-7.5pH is acceptable
effect: abovr 7.5pH this causes excess scale

Next steps: I ordered a digital pH and TPS meters from China for less then 2eur.

Hardness (Calcium only)

The water plant says, we have 75,8mg/l of Calcium
and a total hardness (considering not just the Calcium) of 12.5°dH or 2.19mmol/l
The bottled water says, we have 500mg Ca/l+64mg Mg/l=84,86dH

7°dGH/68mg/l is perfect
17-85mg/l is acceptable (first source).
8-12 °dH is acceptable (second source).
3-7 °dH is acceptable (third source).
Above 85°C this forms scale.
High hardness makes coffee go bitter quickly.
Low hardness supresses the taste of the coffee.

Here is a nice calculator between °dH, mg/l of Calcium-Oxide and ppm CaCO3,...
Or you calculate °dH = 0.1402*[Ca in mg/l ] + 0.2307*[Mg in mg/l ]
Or mmol/l= [Ca in mg/l] / 40 + [Mg in mg/l] / 24,3 .

Sodium (DE: Natrium)

The water plant says, we have 10.2mg/l.  But ADD what the water filter releases.
The bottled water says, we have 18.0mg/l

10mg/l is perfect.
Anything near that level is acceptable.

The problem may of cause also be that the water filter with my very hard water (12.5°dH or 2.19mmol/l) releases enough sodium (DE: Natrium) to exceed 10mg/l.
The original water already has 10.2mg/l and is thus at the brink of the acceptable level.
Above 50mg/l this seems to cause a sour flavor. (Very low sodium levels seem to cause sweet flavors. That sounds very interesting as it's a taste I generally like.)

TDS=total dissolved solids

The water plant says, we have 75.8mg/l of Calcium + 7.3mg/l Magnesium + 10.2mg/l Natrium+1.7mg/l potassium (DE: Kalium)
= 95mg/l  I'm not sure I did this calculation correctly and am not missing anything.
The bottled water says, we have 500+29.0+64.0+18.0+5.0=616mg/l

150mg/l is perfect
75-250mg/l is acceptable.
low=overextraction, tannic taste (DE: Gerbsäure), dry mouth
high=mineral taste, overextraction

Total alkalinity

The water plant says, we have TODO
The bottled water says: 1130mg/l of Sulfate + 414.0mg/l of Bicarbionate (DE: Hydrogencarbonat)
TODO: I need to refresh my chemistry on this topic.

40mg/l is perfect.
Anything near that level is acceptable.
effect: high=gum up outher layer of coffee and cause uneven extraction. Also scale buildup.


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