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December 04, 2019 /
What can we use to remineralise water?

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 writing the post, a few people have written in to ask how to extend this method to use other mineral salts. We’ve written this post to make it as easy as possible to make your water with any mineral salts you would like to experiment with.

The bad news is that in order to do this, you will need to do some basic maths, and a little research into what your mineral contains. The good news is that in this post, we’ve tried to simplify these concepts as much as possible, so that even if you don’t understand the chemistry, you should be able to expand your water repertoire by following these instructions.

 

 

What minerals can we use?

The idea with this post is that you can use anything you like, as long as it’s food safe! However, there are a few commonly used minerals to consider.

Hardness

  • Calcium Chloride
  • Calcium Sulphate
  • Magnesium Chloride
  • Magnesium Sulphate

Alkalinity

  • Sodium Bicarbonate
  • Potassium Bicarbonate

Both
These minerals are hard to dissolve, so for that reason we don’t recommend using them. If you want to try using these, you can carbonate the water using a sodastream to make them dissolve, but we find there are easier ways to get similar results.

Other

  • Sodium Chloride
  • Sodium Hydroxide
  • Hydrochloric Acid
  • Sodium Citrate

Calcium and magnesium minerals are responsible for hardness and give your extraction power, and the bicarbonates or carbonates add buffer, to moderate the acidity. These are the major components that control the way the water affects your coffee.

The chloride and sulphate ions don’t seem to have much effect on flavour at the concentrations we typically use, but can be corrosive or impart off flavours at high concentrations.

Sodium may have some effect in extraction, but too much will lend a salty taste to the water. Salt has also been reported to reduce perception of bitterness in small amounts (P. A. S. Breslin & G. K. Beauchamp, 1997).

Sodium Hydroxide and Hydrochloric Acid are used by Chris Hendon and Maxwell Colonna-Dashwood in “Water for Coffee” to control pH. However, because these chemicals are dangerous without careful handling, we don’t recommend using these.

Finally, Sodium Citrate is an ingredient in Third Wave Water, used as a buffer instead of bicarbonates. Using this correctly is a little more complicated and beyond the scope of this article, as it’s an organic molecule rather than a mineral, but we’ve listed it for completeness, should anyone want to experiment with it.

 

 

How much to use?

It’s maths time! The first step is to work out exactly what the content of your mineral is. Many common minerals exist naturally as a ‘hydrate’, meaning they include water as part of the crystal structure  — for example, Epsom Salts are actually Magnesium Sulphate Heptahydrate (MgSO4.7H2O). This should be listed by the manufacturer, but if in doubt, check online for the common form of the mineral and what it should look like.

Once you know what you have, you need to know the molecular weight of the mineral  — and rather than revising your high school chemistry, you can just Google the answer: for example, searching “molecular weight of magnesium sulphate” gives me the answer: 120.366 g/mol.

You then need to add the molecular weight of the water in the crystal — 18 g/mol for each water molecule. So for our example with Epsom Salts: 120.366 + (7 × 18) = 246.366 g/mol

Hardness

To work out how much of a calcium or magnesium mineral you need to add to 1L of water to get a certain hardness, just divide that number by 100,000 then multiply by the number of ppm hardness you require.

So here’s how to get 100ppm of hardness, using our example of Epsom Salts: 246.366 ÷ 100000 × 100 = 0.246g added to 1L water.

Alkalinity

To work out how much of a bicarbonate you need to add to 1L of water to get a certain alkalinity, just divide the number by 50,000 then multiply by the number of ppm alkalinity you require.

So, using Google we find that the molecular weight of sodium bicarbonate is 84.007 and it contains no extra water (anhydrous). To get 100ppm of alkalinity: 84.007 ÷ 50000 × 100 = 0.168g added to 1L water.

If you do use magnesium carbonate, then for both hardness and alkalinity, just multiply your desired ppm by 0.00084, then use that many grams in a litre of water.

 

 

And then?

That’s pretty much it! To confirm you got the KH and GH you intended, you could use a drop kit to measure the water you’ve made. We don’t know much about how other minerals affect the taste of coffee, so for those minerals (such as table salt), trial and error is the way to go. If you want to tweak pH, the easiest way is to use a pH meter and add your acid or base dropwise until you get the pH you want, but bear in mind that this will also affect the alkalinity.

Weighing such small amounts accurately is hard and needs special scales, which is why we use concentrates. You might find it easier to weigh out ten times as much as you need, then dilute the concentrate 1:10.

Look out for any cloudiness or white deposits at the bottom of your container  — this tells you some minerals didn’t dissolve, or reacted together to form something that doesn’t dissolve, which will throw off your calculations.

Lastly, a warning: don’t put remineralised water in your espresso machine unless you’re very sure what you’re doing (in which case, you probably don’t need this post!). If you create super-hard water and scale up your kettle, it’s fairly easy to fix  — but descaling an espresso machine is no fun at all.

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Stijn Mulder
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Stijn Mulder

About adding the magnesium hydrate, I don’t really grasp the simplified mathematics:
Wouldn’t you want to add 0.01 mass-% off magnesium-ions into the solution if you want 100ppm concentration?
0.01% of 1000gr (weight of 1 liter water) would be 0.1 gr of magnesium in solution. The molecular weight of magnesium is approximately 24 gr/mol, 0.1gr / 24 = 0.0041 mols of magnesium and therefore 0.0041 of magnesium-hydrate since each molecule contains one Mg atom. 0.0041*246 = 1gr of Mg-hydrate…..???
Or did my chemistry became mega rusty hahaha

BHLearn
BHLearn

Hi Stijn – we’re aiming for 100ppm of hardness (expressed as CaCO3 equivalents), rather than 100ppm of magnesium ions. Hope that makes it clearer!

Ghazi
Guest
Ghazi

I have found Potassium Bicarbonate’s molecular weight to be 100.115. So with the maths included I come up with 2g per liter of distilled water for concentrate. Which should give me the same results for targeting a specific KH or GH as the Sodium Bicarbonate 1.68 in your updated water recipe. I could not find if it was Heptahydrate or Anhydrous and most suppliers do not state.

Do you know if Potassium Bicarbonate is in fact anhydrous ? Otherwise how would I do the maths if it was a Heptahydrate?

Thanks a lot for this article.

Ghazi

BHLearn
BHLearn

Hi Ghazi, Potassium Bicarbonate will be anhydrous. Happy mineralising!

Ghazi
Guest
Ghazi

Potassium Bicarbonate KHCO3 is a heptahydrate or at least the one I got. So with the maths included

100.115 + 126 = 226.115 ÷ 50,000 x 100

= 4.5g per litre of concentrate

Ghazi
Guest
Ghazi

Hello. Sorry the weight for KHCO3 is

100.115 + 108 = 208.115 ÷ 50,000 x 100

4.2g per litre

Please someone correct me if am wrong

Thanks

Jonas
Guest
Jonas

Is there any way you could explain how to remineralise water for espresso machines? I’ve been making my own water for filter brewing for quite some time now, but the water for my espresso machine has always been a problem to get right, as filtered tap water isn’t good enough.

Ant
Member
Ant

How about RO with bypass?

Philip
Guest
Philip

RO would be pointless in espresso since the extraction ratio water:coffee is so low. Where pourover may be 17;1 espresso may be 2:1 so ideally the mineral content could be x8 more concentrated.
It is for this reason I use a ROK manual extraction which is easy to clean and affords pressure profiling

BHLearn
BHLearn

Hey Jonas, You’ll find three detailed lessons on this in chapter 4 of The Water Course which is one of our online courses included in the BH Unlimited subscription.

Ant
Member
Ant

Why is the alkalinity bit divided by 50000?
I can understand if you are using calcium/magnesium bicarb, but sodium bicarb should only contain one HCO3- group? Or am I being daft
Thanks

David
Guest
David

You’re not being daft. It’s because with bicarbonates there are twice as many carbonates than sodium/potassium, so dividing by 50,000 is the same as dividing by 100,000 and then multiplying by 2. That part could’ve explained a little better, but it is correct.

BHLearn
BHLearn

Hi Ant – David is correct, on all counts. We skipped over this to avoid a long explanation! Firstly, why 100,000? It’s the molecular weight of CaCO3 (100), which is our reference molecule, multiplied by 1000 to convert from g to mg/L. For Bicarb, it’s then half that: 50,000, because you need 2 bicarbonates to make one CaCO3 equivalent. To understand why two bicarbs is equivalent to one carbonate, remember the function of the carbonate/bicarb is to buffer the acidity by removing H+ ions. CaCO3 can neutralise 2 H+ ions (CaCO3 + 2H+ → Ca2+ + CO2 + H2O) while… Read more »

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