Pre-conditioned mash water with acid, undershot pH

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gifty74

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So this discussion got a little lost in another thread I had started, so asking the question here to hopefully get a better response. The scenario is I was working with one grain bill from a previous batch, and realized I overdosed with phosphoric acid (85%). I replicated close to the very same grain bill, same water, etc, and this time pre-conditioned the water with half of the acid I used before, 2.5ml. After doughing in, and waiting 15 min I checked the pH and it came out to 5.02. Way low obviously, so trying to determine what changed. Thinking back, I did change base malts from a 2-row/Maris Otter blend to all Briess 2-row (15lb). I also used caramalt instead of 10L crystal (1lb), but those should be about the same. 1lb of Munich in both. So I'm hypothesizing that the base malt had that big of a difference in buffering capacity. Is this possible? All 2-row batch mash pH ended up at 5.02 with 2.5ml of acid pre-dosed. The 2-row/MO batch ended up at 5.2 with 5.0ml of acid added to the mash. Might just have to do mini-mashes tonight on the stove to see is the malts are really at fault.
 
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