Adding minerals to R.O. water: does the order matter?

[ocluke]

I use the donation version of Bru'n Water spreadsheet to calculate my brewing water profiles, and I always use 100% reverse osmosis water and build the profile (my municipal water switches wells throughout the year, so this provides me a reliable starting point).

The additions I use to build my water profile are:

• Gypsum
• Espsom salt
• Calcium chloride
• Baking soda
• Canning salt
• Lactic acid

I usually select the option to use Gypsum and Calcium Chloride to replace Lime and Chalk in the sparge water.

My question is: can all of the ingredients be measure out into the same plastic cup and then dumped into the water together, or should they be added in a specific order to ensure that the proper chemical reactions occur? I realize that lactic acid should be added separately (before the others, I think). Any insight that someone can provide (ideally siting a source or providing an explanation), would be greatly appreciated.

 

[ocluke]

I'll reply to my own question because Martin Brungard was nice enough to answer it, and I thought that it might help someone else who might have the question

Martin's answer:

All of the minerals and acids should be added all at once to each batch of mashing water and sparging water before any grains are added. It doesn't matter what is added first.

 

[ajdelange]

The only reaction that will take place in the treatment of water is where acid is being added to neutralize the source water alkalinity. For example using lactic acid for this purpose.

HCO3- + HLac ---> H2O + CO2 + Lac-

It obviously doesn't matter whether the acid is added to the water before or after any other salts are added as there as these don't react and even if they did (if the water is very hard phosphoric acid will react with the calcium and precipitate some of it) it still wouldn't matter what the addition order is as long as the species mix. So yes, you can mix all the salts together in the same container and dump it it. Or you could dissolve all the salts in a few hundred mL of water, add the acid, mix that all up and dump that solution into the water. Or you could mix the salts, dump them in and then add the acid separately. However you do it, if neutralization is part of the game, agitate the water to allow the CO2 to escape.

Perhaps you are thinking of the old "Do what you oughter, add acid to water" rhyme. There is a reason for this but it is safety related, not to the extent to which reactions take place.

 

[jdieter]

I underlet my mash tun with untreated RO water with a continuously running stirrator. I pull a small amount of wort and add the salts returning the mixture to the MT asap. Is my practice compromising the mineral treatment of the mash.

 

[ajdelange]

Depends on how well you mix in the returned wort. It is pretty easy to see that you have a uniform mix at strike (no dry spots, no dough balls...) but not so easy subsequently. This implies that it is the best policy to mix salts (and acids/bases) with the strike water. The exception would be where you cannot do that, e.g. an acid addition for measured mash pH correction.

 

[jdieter]

I use Bru'nWater and consistently hit my target mash pH so I'm assuming I have enough mixing going on with my stirrator setup. Is that a reasonable conclusion? It's doable, but would be painful to change my setup to mix the salts in the HLT.

 

[mabrungard]

I use Bru'nWater and consistently hit my target mash pH so I'm assuming I have enough mixing going on with my stirrator setup. Is that a reasonable conclusion? It's doable, but would be painful to change my setup to mix the salts in the HLT.

I guess if you are happy with the results and confident that the mixing is thorough, then it should be OK. But I have found it far easier to add salts and acids to water and be able to visually assure myself that they are fully mixed in the liquor before adding grain.

I am still quite confused by the premise that preparing all brewing liquor for the entire mashing and sparging volume, all at once, is easier or worthwhile. I've always prepared my mashing liquor separately and sparging liquor separately. On a thermodynamic level, there is only a small difference in the heating. Each smaller liquor volume heats quicker. I've also only had one kettle and one burner for liquor heating, so I know that not having a separate HLT does not prevent a brewer from heating separate liquor batches. Since we know that the alkalinity needed for mashing and sparging water can differ, it just doesn't make sense to ham-string water preparation in that way.

PS: due to that thermodynamic thing mentioned above, preparing the mashing and sparging water separately does shorten your brew day since you can mash sooner and the preparation of the sparging water is done during the mashing period while you are waiting.

 

[jdieter]

My well water isn't suitable for brewing almost any style, Ca>110ppm, Mg>35, HCO3>450, TA>350. So I start collecting enough RO the day prior to brewing, most times around 20 gallons. I mash-in with a combination of RO and hard water depending on the recipe mixing the two waters in the MLT. The remainder of the RO water in the HLT I use to sparge. I suppose I could treat the entire HLT volume but I thought sparging with RO would reduce the tannin risk.

 

[ajdelange]

It's pretty clear that whether it is easier to treat the whole volume of liquor to be used in a brewing session depends on one's equipment and procedures. For me it is much easier. For others, apparently it isn't.

There is no need to treat them separately unless you are adding alkalinity to the mash water which in most cases you shouldn't be doing (though see https://www.homebrewtalk.com/f36/water-chemistry-stout-520841/index2.html#post6774587). Even in cases where alkalinity is augmented it often isn't enough to raise runoff pH overly high prior to reaching target runoff extract level.