Dark grains and 5.2

[diver]

I made four great tasting Oatmeal Stouts and on the fifth one I put 5.2 in the mash. The beer doesn't taste so good. It has a bite to it on the aftertaste, I'm not sure how to describe it, maybe acidic or astringent. I heard on the Brewing Network show that someone said they did the same thing with a stout and it tasted bad and one made without it was good. Anyone know why this would happen? I'm going to try the 5.2 in a Pale Ale but no more with stouts.

[Bugeater]

Did you check the ph of your mash before using 5.2? This sounds like a classic case of trying to fix something that isn't broke. If the stout tasted good without 5.2, you probably did not need it and the addition of it added an undesired taste. On the other hand, a pale ale might require it as the pale grains will not lower the Ph as much as the dark grains in the stout. I would recommend checking your Ph measurements before trying any adjustments.

[TomG]

I've tried it with dark beers without success. I don't know if it changed the taste, but it certainly didn't help the pH. YMMV, Tom