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