Adding minerals?

When adding minerals do you add right before you start on brew day or do you let the minerals sit in the water for a day? I've been reading people doing it differently and do not know if it's a personal preference or a method to the madness?
Also when adding a campden tablet (for five gallon batch) does it significantly change or add minerals that would mess up my water profile for the batch I'm brewing?

 

Nearly all minerals dissolve almost instantaneously, including Campden. You can add them all immediately prior to brewing, no need to add them in advance. The Campden is also immediately effective at eliminating chlorine from your water -- again, there's no need to wait or do it ahead. The chemical reaction there is instantaneous. And it's harmless in beer, you won't be able to taste it unless you do something strange like add several tablets per gallon. 1/4 tablet in 5 gallons is enough in most cases.

The one exception is chalk, which does not dissolve very well. Most people don't use chalk and I wouldn't recommend it because you can get your calcium and carbonate from other minerals that dissolve more easily.

 

Yes, most of the mineral salts used in brewing, dissolve. However, don't just dump them in and let them sit at the bottom of the vessel. You do have to stir the water to help the salts dissolve in a reasonably quick manner. If they aren't dissolved, stir more!

 

And don't be afraid to heat the water to get everything dissolved. Just like dissolving sugar is faster in hot water compared to cold, the minerals will dissolve more easily in hot water, so heat the water if you are having trouble with the minerals taking too long to dissolve.

 

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Of all the things mentioned calcium carbonate is the one that does not dissolve in water without the addition of acid but you aren't going to use that. If you are trying to duplicate a profile from one of the spreadsheets/programs that wants you to use calcium carbonate with acid to get calcium content up, don't. The second least soluble is the Campden tablet or or metabite powder. It is hard to get them to dissolve completely so about the best you can do is crush them with a spoon in some warm water, stir until they are somewhat dissolved and then add the liquid to the water to be treated. See the sticky on Campden tablets. It will also answer your question about what Campden tablets add to treated water.

Next on the list in order of solubility is calcium sulfate (gypsum). It is soluble enough for our purposes but not really that soluble and it dissolves better in cold water than hot. Calcium chloiride, sodium sulfate and sodium chloride are all very soluble. The only one that is going to give you trouble (other than the metabite which you will deal with separately) is the gypsum so do not follow the advice of #4. Even with cold water and a modest addition of gypsum it may take quite a bit of stirring to get it to dissolve completely.

As to when you treat the water it doesn't really matter unless you have added bicarbonates and acids. Such mixtures will change pH and alkalinity as they try to equilibrate with the air.

 

I usually add to the cold water before heating and stir it all up.

Sometimes I get a weird "scum" on the surface of the water before heating it up. Sometimes something doesn't dissolve right away, but with a little agitation it usually mixes in quite well. I almost always add Gypsum, Clacium Chloride and Campden Tab. Rarely I may add a pinch of Magnesium Sulfate (Epsom Salt).