homebrewandbeer.com

Well, I'm fairly new to all of this, but so far (and thanks to your help in the early days) things have been going great.

So great, in fact that my only complaint with my two most recent brews is the presence of a flavor that comes from our tap water supply. It's a kind of metallic chemically taste, it's just as present in a glass of tap water as it is in a glass of beer made from that tap water.

Now, I have a reverse osmosis filter here (not a britta filter, but a real RO filter), and here's my idea...

What I am thinking of is RO filtering some water into a sanitised fermenter, and adding back some minerals to give the water the correct mineral profile for, say - the bavarian alps, or Englands Lake District (insert favourite brewing region here).

That way, if I want to make a lager using Evian - no worries, I'll make something close to Evian.

Thing is, while I've heard that this is done in some commercial brewing, I haven't got a clue how to do this.

Does anyone have any advice on how to obtain the correct mineral salts to make quality brewing water from RO water?

Many thanks

There are a few threads on water chemistry on here already, but generally speaking water chemistry is quite a complex topic, which is covered reasonably well in a fair few brewing books (How to Brew, third edition by John Palmer and The Complete Joy of Homebrewing by Charlie Papazian are perhaps the best-known examples).

I'll try to summarise it off the top of my head for you here though.

Basically it comes down to tweaking the concentrations of various ions using various salts. Calcium Sulphate (gypsum), Calcium Carbonate (chalk), Calcium Chloride and Sodium Chloride (table salt) are the most commonly used.

- Calcium increases hardness.
- Carbonate increases hardness.
- Sulphate increases hop "crispness".
- Sodium (Na): Adds a "fullness" and "sweetness" (accentuates maltiness).
- Chloride increases "fullness" (up to a certain level where it starts to taste "salty").

You need to look at the salt profile of the area you're trying to emulate (see references), then work out what salts to add to give you that profile, keeping in mind the salt profile of the water you're starting with. If you have soft water this comes down to adding up to a teaspoon of gypsum and/or chalk, and/or a rather smaller amount of table salt. If you have hard water, then things are a fair bit more difficult, but your reverse-osmosis filter should solve most of that for you.

If you're not doing all-grain brewing then you're pretty much wasting your time playing with water chemistry, because the greatest effect it has is on the grain enzymes during mashing and the hop isomerisation during the boil. Having said that, using filtered water is absolutely a good idea though if you're noticing bad tastes coming through from your water.

References:
http://www.howtobrew.com/section1/chapter4-1.html
http://www.unm.edu/~draper/beer/waterpro.html
http://www.thekrib.com/Plants/CO2/hard-slu.html
http://www.brewsupplies.com/homebrew_chemicals.htm
http://brewery.org/library/wchmprimer.html
http://www.antiochsudsuckers.com/tom/brewingwater.htm