Parti Gyle Water Chemistry

[SouthBay]

So, i need some help with parti gyle water chemistry.

I've had my tap water tested by Ward Labs, and use Bru'n Water to calculate how much dilution (distilled water, RO water, etc) to add to my tap, and how much/what type of additions to hit my target water profile for a mash. The long and the short of it is that using only my tap water, i can brew a pretty killer stout, but i need to dilute the mash water down for lighter colored amber beers and pale ales.

So, on the ever nearing horizon, i've got my first parti gyle brew planned. I'm going to make an imperial IPA and a mild Rye PA out of the brew. But, i need some help with the water chemistry on the mild Rye.

The grain bill for the first brew, the IIPA, is as follows:

19# US 2 row
2# Munich
2# Caramel 30

For that first beer, i've got my water chemistry all set to go.

Then, after draining the first runnings, i'm going to add about 7 gallons of water, and 2# of Rye malt, and 1# flaked Rye, re-mash, and drain that into the mild.

My question is this: how much residual acidity will remain in the grains after draining the first runnings? how do i calculate the acidity of the mash once i add more water to it, especially when i'm mashing in a few pounds of fresh grist?

Basically, i need to calculate how much distilled water to dilute my tap water with to hit the right PH and what, if any, mineral additions will be necessary. I can post my water profile if needed, but i'm really looking for more of a 'How To.'

Thanks in advance!

 

[SouthBay]

Nothing yet, eh?

So, here's where i'm at with it:
Presumably, the acidity of the grains is going to be diluted as the mash water for the first beer is added. When thats drained away, anyone have any idea what the percentage of acidifying properties of the grains would remain?

FWIW, the gravity will run off about 2/3 of its potential in the first beer. So, maybe if no one has any answers i'll just stick with that ratio, that the second mash will only be about 1/3 as acidic as the first mash.

 

[mabrungard]

The total acidity of the mash would be reduced in the primary mash. The alkalinity of the mash water added would leave you with a small net excess that leads to the appropriate mash pH drop. Since the first runnings are drained, you could estimate the remaining total acidity in the mash as the runnings volume divided by the initial mash water volume.

You can obviously calculate the added acidity that will be added via the Rye added to the grist. That would leave you with the dilemma of figuring out how much additional alkalinity to add via the second water batch. Not exactly easy to figure, but its possible. The thing is that you'll want to end up with a similar net acidity in that second partigyle.

Now you could just punt and assume that the mash pH won't drop too far due to the added Rye. Then you could just forget about the need for adding any alkalinity and use straight RO water to that second mash. I would skip adding any hardening minerals to that second mash and add that mineral dose directly to the kettle to avoid reducing the RA too much.

Please report back with your results.

 

[SouthBay]

Will do.

I played around with brun water this morning, too. Using the same ratio for the gravity to guess at the semi spent grains ability to acidify the second mash, 1/3, I calculated I only needed to replace 1 gallon of tap water with RO water to hit the mineral profile and 5.4 ph.

But, im guessing the grist acidity after the first mash is going to be reduced by more than 2/3, not counting the rye.

Im wondering if I should just calculate the second mash as if it was sparge water, and aim for 5.5ph, which would then hit 5.4 after the rye.

On the other hand, straight ro water should work, and isn't too expensive. Ill let you know what I come up with