Question about the latest release of Bru'n water?

[darynsd]

I received the latest release (v5.3) of Bru'n Water recently. I tend to mash on the thinner side so I was very interested when I read that thinner water/grist ratios should see improved predictions.

I transferred my most recent brew over so comparing the identical input, the pH decreased between v4.2 and v5.3 (from 5.42 to 5.35). I'm using a thinner mash at 2.12 qt./lb. The actual room temp pH measured 5.51 after 10 minutes and 5.48 after 20 minutes. Most references I've read say the pH should increase as the mash gets thinner, not decrease? If I make the mash even thinner, the pH continues to drop? This is opposite of v4.2. What am I missing?

 

[brewgar]

^ Thank you for posting your Bn'W results. Your observations are sharp, and reporting is crucial to refining the models. Brew on!

 

[schematix]

That small of a difference is within the bounds of measurement error.

 

[darynsd]

I agree that the measured pH was pretty close to the prediction from v4.2. It was a little high, but I believe Martin tweaked v5.3 to be more accurate for a thinner mash. I expected that to raise the predicted pH to be even closer to the measurement, but it got further away! Am I wrong that if the only change is an increase in the amount of water in the mash, the mash pH should increase? This is how v4.2 worked, so I'm surprised that it went the other way in v5.3.

 

[ajdelange]

I received the latest release (v5.3) of Bru'n Water recently. I tend to mash on the thinner side so I was very interested when I read that thinner water/grist ratios should see improved predictions.

Where did you read that? If you are mashing with an alkaline water it is true. More water, more bicarbonate, same amount of malt. But if you are mashing with RO water it shouldn't make any difference (or very little as even RO water contains a smidgeon of alkalinity).

I transferred my most recent brew over so comparing the identical input, the pH decreased between v4.2 and v5.3 (from 5.42 to 5.35). I'm using a thinner mash at 2.12 qt./lb. The actual room temp pH measured 5.51 after 10 minutes and 5.48 after 20 minutes. Most references I've read say the pH should increase as the mash gets thinner, not decrease? If I make the mash even thinner, the pH continues to drop? This is opposite of v4.2. What am I missing?

You aren't missing anything. As the mash becomes thinner the pH should rise (though the rise will be slight with low alkalinity water). It should never fall. There is some problem in Bru'n water's model of the interaction of malt and water borne bicarbonate. This was pointed out in a rather lengthy thread ("Thought Experiment") and supposed to have been fixed. The semi-emprical models of the early (Gen I) spreadsheets don't seem to be able to be fit to the actual chemistry under all conditions.

 

[darynsd]

Where did you read that? If you are mashing with an alkaline water it is true. More water, more bicarbonate, same amount of malt. But if you are mashing with RO water it shouldn't make any difference (or very little as even RO water contains a smidgeon of alkalinity).

Martin wrote in the email distributing v5.3 that "calculations for thin mashes are improved". Thanks for the clarification about using RO water. I typically do. There's a lot to learn! Unfortunately with the new calculations, I'm even further off than I thought.