What Mg and Ca compounds to add to water if you must

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
coffeeOnTheBrain

#1: Post by coffeeOnTheBrain »

I have mixed bottles of mineral water, tested designer recipes, and altered recipes based on my taste preference. I did that mostly for pour over as I was never really comfortable feeding my precious espresso machine with designer water. I have the fear of damaging my machine with scale or corrosion.
The LSI formula to calculate if the given amounts of chemical compounds are safe depending on temperature weren't really helpful either. Owning a HX machine the temperature range between the boiler and the group is pretty wide with about 40 degrees. That would be somehow manageable, but I turn the machine of every day, so the range is basically 110 degrees. For a 110 degrees temperature range it is impossible to find a water recipe that is inside SCA range and deemed safe by the LSI formula.
I recently read a bunch if not all posts of Dr Pavlis about water chemistry here on the forum. I was actually sad that my fear of feeding my espresso machine with pure water and some added chemical compounds is pretty rational.
As part of his career as a Chemist and Professor Dr. Pelvis did research that is relevant to scale and corrosion in espresso machines. Therefore I believe more his posts than articles by coffee professionals that focus more on taste than on actual chemistry and in some cases do not even mention the danger of corrosion and scale. Didn't we all hear of a coffee shop which ruined expensive espresso machines with the wrong inline filter or maybe a wrong choice for the chemical compounds added.
Back to Dr. Pavlis, he has a very unique approach to water additives for espresso. He claims that only KHCO3 should be used to create water for espresso. KHCO3 raises the alkalinity, but doesn't affect hardness.
There are 2 main factors in water for coffee alkalinity and hardness. There are varying targets for those factors and a mostly agreed on acceptable range. He claims that one doesn't need to raise hardness for a good tasting espresso. He does acknowledge that there are other taste preferences though. However the SCA and a bunch of coffee professionals deem hardness a very important factor.
Furthermore Dr. Pavlis says that basically any chemical compound that raises hardness is dangerous to espresso machines in different ways.
I believe Dr. Pavlis, but I would like to raise hardness by adding magnesium and calcium to enhance the flavor according to my taste preference anyway, but I would like to minimize the danger of damaging my machine.

Starting from pure water one needs to add chemical compounds to reach a target value. I am wondering which chemical compounds can be used and which drawbacks do they have.
I am not a chemist hence I need your help :)
I will sum up what I have read and would hope for you to chime in.
Also I would like to find out if any other factors are noteworthy, besides alkalinity, hardness, scale, and corrosion. For example SCA sets a target of 10ppm of Na, I am unsure why they do that. To prevent corrosion or scale or maybe for taste. Are there additional factors besides Na?

To reach a target alkalinity one can add NaHCO3 and KHCO3 .
Dr. Pavlis chose KHCO3 as he claims that coffee has a high amount of K anyway and that Na can lead to bad taste in combination with K (if I remember correctly).

For hardness one can add different compounds of Mg and Ca.

CaSO4
CaSO4 seems to be hard to be descaled, but might be usable in kettles or if only using steaming rarely because it is soluble in water as long as the concentration is not to high and the water is able to absorb it and carry it (if I understand correctly).

MgSO4
When used as the only source for hardness and in absence of Cl and Ca, MgSO4 is reported to not cause scale.

MgCl2 and CaCl2
Cl seems to enhance corrosion and scaling, but descaling can be done with light acids.

MgCO3 and CaCO3
Not very soluble, a spritz of CO2 with e.g. a sodastream can help dissolve. By adding one of these PH is not affected, but through chemical reaction with CO2 alkalinity is raised.
While CaCO3 is limescale and precipitation can be calculated with the LSI formula, MgCO3 does not seem to cause scaling problems in coffee boilers that we would expect to see with an equivalent amount of CaCO3.

Ca(OH)3 and Mg(OH)2
Are soluble only in very low concentrations. They react with CO2 to form CaCO3 or MgCO3.

MgO and CaO
Make the PH very alkaline. They react with H2O to form Ca(OH)3 or Mg(OH)2.

Ca₃(C₆H₅O₇)₂
Calcium citrate is an organic carbon ion that potentially could become food for microbe growth.

Important Note
homeburrero wrote: ...
Also, note that if you add a mix of calcium chloride, magnesium sulfate, and sodium bicarbonate, be aware that you have potential for calcium sulfate and calcium carbonate in your mix. Once the salts dissolve and dissociate it is a just a mix of all the ions, and the calcium can combine with sulfate or carbonate even though it was added as chloride.

Did I miss any chemical compounds?
Do the above have other drawbacks that I missed?

A good short read: Boiler-safe level of chlorides (and other compounds) in water

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#2: Post by MNate »

I guess it's the Perger recipe that uses MgSO4, concluding that it does not add scale to boilers because it doesn't dissipate because of the lack of carbonates... or at least those who use it report no scale developing. I just said a lot of words there I don't understand... this thread mentions it:

Argument against magnesium sulphate?

It's what I've been using, but I can't report much about it.

But I guess you're really just asking for other options. It seems to have some things in favor of it though, if it really doesn't produce scale.

coffeeOnTheBrain (original poster)

#3: Post by coffeeOnTheBrain (original poster) » replying to MNate »

Thank you! I just went over the linked thread and it was very informative. Indeed only adding MgSO4 is an interesting approach. Based on user experience it seems not to cause scaling. What about corrosion though? I guess no corrosion either, as that probably would have been mentioned, but in fact wasn't this way or the other in that particular thread. I now wonder what happens to the MgSO4 in the steam boiler, does it leave the boiler with the steam? Even if it doesn't cause scale it has to go somewhere.

PS: I am basically looking for any knowledge or experience what chemical compounds could be added to water to be used in an espresso machine named already or not.

coffeeOnTheBrain (original poster)

#4: Post by coffeeOnTheBrain (original poster) »

Reading a little more I discovered that there are some concerns about MgCO3 and CaCO3 building a basis for organic growth, C might deposit in boilers and both seem to not be present in natural water.

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homeburrero
Team HB

#5: Post by homeburrero »

coffeeOnTheBrain wrote:MgCO3 and CaCO3
What about compounds with C? What are C's characteristics?
coffeeOnTheBrain wrote:Reading a little more I discovered that there are some concerns about MgCO3 and CaCO3 building a basis for organic growth, C might deposit in boilers and both seem to not be present in natural water.
I'm not sure what 'C' here is referring to. The ion in these cases is carbonate (CO3²⁻) and bicarbonate (HCO3⁻) -- inorganic carbon ions which are very common in natural waters. Along with CO2 and carbonic acid (H2CO3) this dissolved inorganic carbon (DIC) is key to the buffered pH of natural water. It's the reason the ocean can absorb tons of CO2 without becoming acidic.

Hard natural water is typically high in calcium and/or magnesium carbonates. And CaCO3 and MgCO3 are commonly used in remineralization cartridges in the form of calcite, aragonite, dolomite, crushed marble, crushed coral, etc to provide a relatively small and predictable amount of hardness and alkalinity to RO water. Once dissolved in the water they react with dissolved CO2 and carbonic acid to form somewhat soluble bicarbonates -- Ca(HCO3)₂ and Mg(HCO3)₂ at near neutral pH values.

Calcium and magnesium carbonate salts can also be used in water recipes but are troublesome because they are not very soluble. Some water recipes use CO2 spritzers like sodastream to help make the salts dissolve.

MgO and sometimes CaO can be used for remineralization in the form of products like Corosex and calcined dolomite. Once dissolved in water they also become bicarbonates. They are much more likely to overcorrect than simple calcite, and can cause a very alkaline pH.

Some recipes use calcium citrate (Ca₃(C₆H₅O₇)₂ as a source of calcium hardness, and unlike carbonate, citrate is an organic carbon ion that potentially could become food for microbe growth.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

coffeeOnTheBrain (original poster)

#6: Post by coffeeOnTheBrain (original poster) »

Thank you for helping and correcting what I messed up :)
I will add your input to the first post.
homeburrero wrote:I'm not sure what 'C' here is referring to.
...
My bad, that was just nonsense on my side, I understand it a little bit better now.
homeburrero wrote: ...
Hard natural water is typically high in calcium and/or magnesium carbonates. And CaCO3 and MgCO3 are commonly used in remineralization cartridges in the form of calcite, aragonite, dolomite, crushed marble, crushed coral, etc to provide a relatively small and predictable amount of hardness and alkalinity to RO water. Once dissolved in the water they react with dissolved CO2 and carbonic acid to form somewhat soluble bicarbonates -- Ca(HCO3)₂ and Mg(HCO3)₂ at near neutral pH values. ...
Now that is awesome! The neutral pH I mean.
homeburrero wrote: ...
Calcium and magnesium carbonate salts can also be used in water recipes but are troublesome because they are not very soluble. Some water recipes use CO2 spritzers like sodastream to help make the salts dissolve.
...
Interesting that a spritz of CO2 helps to dissolve CaCO3 and MgCO3 variants.
homeburrero wrote: ...
MgO and sometimes CaO can be used for remineralization in the form of products like Corosex and calcined dolomite. Once dissolved in water they also become bicarbonates. They are much more likely to overcorrect than simple calcite, and can cause a very alkaline pH.
...
Thank you I never heard of these being an option before.
homeburrero wrote: ...
Some recipes use calcium citrate (Ca₃(C₆H₅O₇)₂ as a source of calcium hardness, and unlike carbonate, citrate is an organic carbon ion that potentially could become food for microbe growth.
Thank you again, I mixed up this and CaCO3.

coffeeOnTheBrain (original poster)

#7: Post by coffeeOnTheBrain (original poster) »

I understand now that CaCO3 and MgCO3 need to react with CO2 to dissolve in water and that HCO3 is one product of the reaction raising the alkalinity of the water. Is there an easy way ti quantify this. I would like to take it into account when making a recipe. Is there maybe even an open excel sheet which does that?

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homeburrero
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#8: Post by homeburrero » replying to coffeeOnTheBrain »

If you quantify your salt in terms of CaCO3 equivalents, then you can easily calculate the hardness and the alkalinity. So for pure CaCO3 it's especially easy - - if you add 10 mg per Liter of water then your hardness and your alkalinity both are increased by 10 mg/L CaCO3 equivalents.

A handy tool you can use for a variety of salts is available from Aqion. Their simple online calculator calculator can be found here: http://www.aqion.onl/show_ph. They quantify hardness and alkalinity in units of meq/L. Just multiply that by 50 to get mg/L CaCO3 equivalent.

Re the underlying reactions, note that these reactions are always happening in water exposed to atmospheric CO2:

CO₂(aq) + H₂OH₂CO₃
H₂CO₃ HCO₃⁻ + H⁺
HCO₃⁻ CO₃²⁻ + H⁺


And the amount of CO₂(aq) in the water can vary. Spritz the water with a sodastream and the CO₂(aq) goes way up and drives those reactions to make the water more acidic. Pull CO₂ out of the water by adding CaO or MgO and it drives the other way and the water becomes more basic. Exposed to air the CO₂ will gradually increase or decrease to equilibrium with atmosphere and the water will return to a predictable pH for its alkalinity level.

Also, when I said: "Once dissolved in the water they [CaCO3 and MgCO3] react with dissolved CO2 and carbonic acid to form somewhat soluble bicarbonates -- Ca(HCO3)₂ and Mg(HCO3)₂ at near neutral pH values." I didn't mean to imply that their addition necessarily causes a neutral pH. I was trying to convey that at a neutral pH they exist primarily as somewhat soluble HCO₃⁻ , bicarbonates. At a high pH they shift to CO₃²⁻⁻ , carbonates, which are relatively insoluble an likely will precipitate out as scale. Below a pH of around 4.5 the bicarbonates are mostly gone, having shifted toward carbonic acid. When you measure alkalinity with a drop titration kit you are essentially measuring how many drops of acid you can add before the pH hits around 4.5, which is the point where all the HCO₃⁻ in the water sample has been used up in buffering the drops of added acid.

Also, CaCO3 and MgCO3 both contribute to hardness, but they don't cause scale in the same way. CaCO3 is limescale, and is a common scale problem that can be roughly predicted with simple equations like the Langelier Saturation Index (LSI). MgCO3 has no easy prediction equation like the LSI, is more soluble at near neutral pH, and may precipitate primarily as Mg(OH)₂ rather than MgCO3 at high pH. MgCO3 does not seem to cause scaling problems in coffee boilers that we would expect to see with an equivalent amount of CaCO3.

Also, note that if you add a mix of calcium chloride, magnesium sulfate, and sodium bicarbonate, be aware that you have potential for calcium sulfate and calcium carbonate in your mix. Once the salts dissolve and dissociate it is a just a mix of all the ions, and the calcium can combine with sulfate or carbonate even though it was added as chloride.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

coffeeOnTheBrain (original poster)

#9: Post by coffeeOnTheBrain (original poster) »

Thank you again for all the input!!! I feel like learning more reading one of your post than reading 10 times that before.
homeburrero wrote:If you quantify your salt in terms of CaCO3 equivalents, then you can easily calculate the hardness and the alkalinity. So for pure CaCO3 it's especially easy - - if you add 10 mg per Liter of water then your hardness and your alkalinity both are increased by 10 mg/L CaCO3 equivalents. ...
I was unable to see the forest for the trees.
homeburrero wrote: ...
A handy tool you can use for a variety of salts is available from Aqion. Their simple online calculator calculator can be found here: http://www.aqion.onl/show_ph. They quantify hardness and alkalinity in units of meq/L. Just multiply that by 50 to get mg/L CaCO3 equivalent. ...
Excellent! The tool seems to have a complete list of all minerals one could add.
Looking a little bit in your first statement in the tool I realized, that not only CaCO3 and MgCO3, but also CaO, MgO, Ca(OH)3 and probably some more chemical compounds always raise alkalinity as well as hardness in the same amount if counted as CaCO3. Therefore one will always end up with the exact same value for alkalinity and hardness if not using CaCl, MgCl, CaSO4, MgSO4 or chemical compounds which I believe can be harmful in pretty low concentrations like Phosphor or Mangan.
Hence some recipes with an alkalinity of 40ppm as CaCO3 and a hardness of 80ppm as CaCO3 can not be achieved without using SO4 or Cl compounds.
Am I thinking straight? Or is there some catch that I have overlooked or maybe other chemical compounds one could use?

homeburrero wrote: ...
Re the underlying reactions, note that these reactions are always happening in water exposed to atmospheric CO2:

CO₂(aq) + H₂OH₂CO₃
H₂CO₃ HCO₃⁻ + H⁺
HCO₃⁻ CO₃²⁻ + H⁺


And the amount of CO₂(aq) in the water can vary. Spritz the water with a sodastream and the CO₂(aq) goes way up and drives those reactions make the water more acidic. Pull CO₂ out of the water by adding CaO or MgO and it drives the other way and the water becomes more basic. Exposed to air the CO₂ will gradually increase or decrease to equilibrium with atmosphere and the water will return to a predictable pH for its alkalinity level. ...
Using a spritz of CO2 is very interesting. Is it necessary for achieving a hardness of 60 or 90 with let's say only CaCO3? I am asking because I think it might be pretty hard to have constant results with it. Or should I just mix, spritz and shake the water until all bubbles are gone?
homeburrero wrote: ...
Also, when I said: "Once dissolved in the water they [CaCO3 and MgCO3] react with dissolved CO2 and carbonic acid to form somewhat soluble bicarbonates -- Ca(HCO3)₂ and Mg(HCO3)₂ at near neutral pH values." I didn't mean to imply that their addition necessarily causes a neutral pH. I was trying to convey that at a neutral pH they exist primarily as somewhat soluble HCO₃⁻ , bicarbonates. At a high pH they shift to CO₃²⁻⁻ , carbonates, which are relatively insoluble an likely will precipitate out as scale. Below a pH of around 4.5 the bicarbonates are mostly gone, having shifted toward carbonic acid. When you measure alkalinity with a drop titration kit you are essentially measuring how many drops of acid you can add before the pH hits around 4.5, which is the point where all the HCO₃⁻ in the water sample has been used up in buffering the drops of added acid.
...
I will try to formulate that more clear in the first post, thank you!
homeburrero wrote: ...
Also, CaCO3 and MgCO3 both contribute to hardness, but they don't cause scale in the same way. CaCO3 is limescale, and is a common scale problem that can be roughly predicted with simple equations like the Langelier Saturation Index (LSI). MgCO3 has no easy prediction equation like the LSI, is more soluble at near neutral pH, and may precipitate primarily as Mg(OH)₂ rather than MgCO3 at high pH. MgCO3 does not seem to cause scaling problems in coffee boilers that we would expect to see with an equivalent amount of CaCO3. ...
I will add that above too.
homeburrero wrote: ...
Also, note that if you add a mix of calcium chloride, magnesium sulfate, and sodium bicarbonate, be aware that you have potential for calcium sulfate and calcium carbonate in your mix. Once the salts dissolve and dissociate it is a just a mix of all the ions, and the calcium can combine with sulfate or carbonate even though it was added as chloride.
That is a very good point I'll add that above and highlight it.

coffeeOnTheBrain (original poster)

#10: Post by coffeeOnTheBrain (original poster) »

As a takeaway I will try a new recipe for my pour over water and 2 recipes for espresso water.

I am not knowledgeable at all, so try these recipes at your own risk.

I will try the original Pavlis recipe and compare it to my own with added CaCO3 and MgCO3.
I will make a concentrate with 2.3g of each in 1l of water and use 10ml per liter brewing water. This should give me about 50ppm of hardness and alkalinity. So it has the same alkalinity as Pavlis water but a much higher level of hardness compared to Dr. Pavlis 0ppm hardness ;)
The result of the LSI formula looks ok.
This way I will be able to decide if I can live with the 0ppm hardness in water for espresso and I am save from Cl and SO4 :)

For the pour over water I will use
1.3g of MgCO3
2.6g of CaCO3
9.6g of MgCl2 6H2O
or should I rather use MgSO4 7H20?
Anyway I am aiming for 40ppm alkalinity and 88ppm hardness. And an amount of Ca of just about 10ppm for my taste preference.