Calculating SRM of Parti-Gyle

So I have a hard time reading math typed out, so I just took pics of my chalk board.
I'm not sure if I'm doing these calculations right. I made the assumption that color extraction was proportional to sugar extraction. That's color in MCU's, not SRM.

Well, I guess I'll just brew it and see if these numbers look right....

I believe your assumption is wrong.

MCU =(lovibond of grain * Grain weight)/ volume of batch

your SRM equation is right, but you miscalculated your MCU

The volume used in the equation should be you batch/final volume.

22.8 SRM just from 1.8*L 2-row is way off, 4.37 SRM for 16 lbs at 1.8*L

I get 21.27 SRM for the batch

By my calcs in Promash, with that grainbill for a total of 9.2 gallons, the total SRM would be 15.9 -- let's say 16. According to the Mosher partigyle guidelines, when you do a 1/3 - 2/3 split of that 16 SRM, it would result in 24 SRM for the 1.078 big beer and 12 SRM for the 1.039 small beer (at 75% efficiency).

hopsalot said:

I believe your assumption is wrong.

MCU =(lovibond of grain * Grain weight)/ volume of batch

your SRM equation is right, but you miscalculated your MCU

The volume used in the equation should be you batch/final volume.

22.8 SRM just from 1.8*L 2-row is way off, 4.37 SRM for 16 lbs at 1.8*L

I get 21.27 SRM for the batch

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Is the 22.8 your referring to on the bottom left of figure #1? If so that is the MCU from that grain before being divided by any volume.

Is that 21.27SRM for the both the 3.2gal and 6 gal batch combined?

michaeltrego said:

By my calcs in Promash, with that grainbill for a total of 9.2 gallons, the total SRM would be 15.9 -- let's say 16. According to the Mosher partigyle guidelines, when you do a 1/3 - 2/3 split of that 16 SRM, it would result in 24 SRM for the 1.078 big beer and 12 SRM for the 1.039 small beer (at 75% efficiency).

Click to expand...

Cool thanks. Those number don't seem that far off from what I came up with (and off in the right way as it's not exactly the same).
That spread sheet looks quite useful, I'll try figure out what formula they used for it. But not right now, as I'm in the middle of a bottling operation.

so you your total volume is 9.2 gal?

I get 6.73 SRM for the 3.2gal batch

and 19.76 SRM fo the 6gal batch

I dont know if you still sum the MCU's then calculate the SRM like you would if it was one batch with the same volume, so I am going to step out of this one.

hopsalot said:

I dont know if you still sum the MCU's then calculate the SRM like you would if it was one batch with the same volume, so I am going to step out of this one.

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Well, I don't really know the right way to do this either, but thanks for trying. I'll be making this tomorrow, so I can see if the original calculations are about right (wish I had some way of testing, other than "eyeballing it").

DrJerryrigger said:

Well, I don't really know the right way to do this either, but thanks for trying. I'll be making this tomorrow, so I can see if the original calculations are about right (wish I had some way of testing, other than "eyeballing it").

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Right on, post your results

hopsalot said:

Right on, post your results

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will do! I'm mashing right now. I'm sure things will work out differently than predicted, but I'll go back and calculate with the volumes and SG that I end up with, to see how things work out.

DrJerryrigger said:

will do! I'm mashing right now. I'm sure things will work out differently than predicted, but I'll go back and calculate with the volumes and SG that I end up with, to see how things work out.

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I'm curious about your parti-gyle session - how did it go?

michaeltrego said:

I'm curious about your parti-gyle session - how did it go?

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poorly, in fact it's still going. It's been three days!

Three days....I thought you were brewing yesterday?

michaeltrego said:

Three days....I thought you were brewing yesterday?

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I started early. Anyway I'm boiling now. It will take some time to figure out my notes. I really botched the calculations on this SRM thing because of a sparging technique I tried. I mashed 7lb of base, and use the sparge from that as the mash and sparge water for the second mash. I should have used the other grain in that, but I'll see if I can figure out what ended up happening, and calculate from that. It's been a long few days. I need a shower and a clean shirt.

SRM = 12.7*A430 = 12.7*e*c*1 where A430 is the absorption in a 1 cm cell at 430 nm, e is the extinction coefficient and c is the molar concentration. Making lots of somewhat shaky assumptions one can reason, therefore, that a 20 °P wort from a parti gyle mash would have twice the SRM of a 10 °P wort from the same mash (because °P, while they are not a molar concentration unit reasonably closely approximate one). Thus, if you believe in the commonly used MCU scheme for calculating color and you treat both gyles the same with respect to length of boil then you might be able to come up with rough estimates of the color by linear apportionment.