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I always use RO water to brew. I have never checked mash PH but have become concerned since my brews have come out darker than predicted by BrewSmith.

I thought (I read in How to Brew by Palmer) that adding some DME to the mash will normalize mash PH. So that is what I have done.

Is RO water not the way to go? Or should I be paying more attention to mash PH on lighter beers? Is there a rule of thumb?

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up vote 3 down vote accepted

For the best results, you should always check your pH and adjust if necessary. Using RO water doesn't change anything. Remember, it's the pH of the mash, not the water, that matters. As pointed out above, you will also need to adjust the mineral content of your water for flavor. That will likely also have an effect on the pH.

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What minerals/salts/adjunts would be needed? Is there a "kit" of additives that I can get? – Reed Feb 13 '14 at 20:19
Calcium sulfate (gypsum) and calcium chloride are the 2 that are generally most useful. But I would recommend adding anything until you get an analysis of the water you're using for a baseline. IF your very hoppy bees don't seem to have enough bitterness and a dry finish, you could experiment with adding a tsp. or 2 of gypsum to the kettle. Beyond that, I wouldn't advise adding anything without an analysis and using a water spreadsheet to calculate additions. – Denny Conn Feb 13 '14 at 22:06

You'll get more browning with higher pH, but there are also plenty of other reasons for producing a darker wort, so you'll need to at least check the pH before deciding to do anything about it. Ideally your pre-boil pH should be around 5.3-5.5 - lower is better.

While adjusting pH may help you with the color, you should be adding minerals to the RO water for the benefit of mash efficiency, flavor, stability and yeast health. In particular Calcium a key constituent in brewing liquor.

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