mineral concentrations based on pre boil or post boil volume?

So my question relates to the water chemistry primer.

Say that you want a baseline water profile with 1 gm cacl per gallon. My question is related to boil off. Would you treat the water based on your pre boil water volume or your post boil volume?

Similar to how o.g. incresases as the liquid is boiled off, does the cacl (or other mineral additions) concentration increase as liquid is boiled off?

For instance if your preboil volume is 9.25 gallons and you treat with 9.25 gms of cacl but then boil down to 7.0 gallons I assume you now have greater than a 1 gm per gallon ratio of cacl

I realize that the difference is negligible and I wouldn't likely be able to taste the difference. I am just curious for my own understanding.

normally when you are talking about your water profile, its talking about the water as it is as it comes out of the tap, not post-boil.

the boil will change the concentrations slightly, sure. but no one is measuring the water profile in a finished beer (theres too much beer in the water at that point!). its always measured before starting the brew process.

+ 1 to Audger. There are also all sorts of reactions and activity that further alter the ionic content of the water throughout the brewing and fermentation process that we can't really quantify. Therefore, using the pre-boil water volume is most appropriate.

Specific to chloride & sulfate, does anyone have a feeling if those are involved in reactions during the boil that would change their concentrations more than just boiling off some water?

Chloride is a very soluble ion and it does not participate in many adsorptive or precipitative actions in the boil or in the environment. I'm currently preparing a presentation on Chlorides in Wastewater for a professional organization I'm a member of.

I am not sure if sulfate participates in many reactions in the boil that would alter its concentration (other than the concentrating effect of boiling off water). But, I doubt that sulfate does.

There are 2 goals in brewing water treatment. One is to get the mash pH to the proper value. This involves calcium, to a lesser extent magnesium and bicarbonate. Calcium and magnesium are precipitated to some extent as part of the reactions which help to establish mash pH and so are reduced (though the malt puts some back in). The other ions (the so called stylistic ions - chloride and sulfate) do not take place in such reactions and so stay pretty much at the initial concentrations as modified by the effects of boil off. Think of the control of these as similar to salting stew. If the beer manifests too much sulfate or chloride be aware that a large evaporative loss in the kettle will concentrate them and reduce them in the mash water.

As beer/wort with active yeast in it is in a reduced state some sulfate gets reduced to sulfite. This is especially noticeable with lager strains. The brewery often smells "like a paper mill" to quote one brewing friend of mine. Some of this gets further reduced to sulfide (jungbuket and the source of sulfide for skunking in light struck beer) but I don't think that's responsible for much reduction in the the original water's sulfate content.