Parti-gyle: Please Check My Math

I'm planning my first parti-gyle next month. It will be a doppelbock/alt. I've run the calculations through and they work out on paper, but this is one of those things that I have been working on so long that I can't quite see the forest for the trees any more. I want to make sure that my math is solid.

The base recipe is follows:
18 lb Munich 10
2 lb Pilsner
1/2 lb Melanoidin
1/4 lb Carafa III

I plan on making 5.25 gallons of Doppelbock and 3.25 gallons of alt. Assuming 70% efficiency, that gives me 523 gravity points to work with. I will extract approximately six gallons of wort each with both the first and second runnings. I plan on taking two gallons from the second runnings and adding them to the doppelbock; then I will do a very long boil to get down to the proper final volume. The alt will get a regular 60 minute boil.

I'm getting a OG of 1.068 for the doppelbock and 1.051 for the alt. But just looking at that, the math does not seem right. Please someone confirm this for me!

I've recently been reading into Parti-gyle so I'll take a stab at it. Assuming your numbers of 523 points extracted over two 6 gallon runnings (12 total) is correct, I get about the same as you. Per Mosher (Radical Brewing) I will assume that the first runnings contain roughly half the sugars and the second and third runnings contain 1/3 and 1/6 respectively. In your case, we're just adding the 2nd and 3rd together as one.

523 points total = 261.5 per batch
Each batch contains 6 gallons = 43.58 points per gallon
Add 2 gallons to first batch = add 87.16 points
Total points, volume of batch 1 = 348.66 @ 8 gallons
Subtract 2 gallons from batch 2 = remove 87.16 points
Total points, volume of batch 2 = 174.34 points @ 4 gallons

Post-boil volume Batch 1 of 5.25 gallons (348.66/5.25) = 1.0664
Post-boil volume Batch 2 of 3.25 gallons (174.34/3.25) = 1.0536

I hope I didn't flub anything up there! Good Luck!

On second thought, after review some info on conversion efficiency based on mash thickness found here (http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Conversion_efficiency) I think we may be significantly off based on your mash thickness.

If you are doughing-in with about 8.5 gallons of water to yield you 6 gallons of first runnings, then that would give you about 1.65 QT/LB. According to this, you'd be getting more around 1.075 @ 6 gallons for your first runnings. That would not leave you much sugars for a 6 gallon batch sparge.

Sorry, someone with more experience will have to chime in here!

Parti-gyle is pretty cool, it will be a fun brew day. My initial reaction is that the gravities you plan for the two beers are too close together. This will require some blending of first and second runnings for both beers, which I did once and it was a PITA.

My advice is to focus on hitting the numbers dead-on on the first beer. Then let the second beer just be what it is based on the volume of wort you have. You can then adjust hopping based on the intended ibu:gravity ratio. But with some planning, you should be able to get pretty close.

As far as figuring out the mash numbers, do you have a brew log that you can look back into previous mashes? Specifically, it would be good to know:

water:grist ratio
volume of 1st runnings
gravity of 1st runnings

With this info you can figure out your conversion efficiency (based entirely on crush unless your pH and/or temp are way off) based on the braukaiser link above. This will let you calculate the volume and gravity of your first runnings based on total lb of grain and mash thickness. From there, apply the rest of your efficiency calcs to tell you the gravity and volume of your second runnings.

You might consider doing 3 runnings to get a little more effiency but also to allow for blending back in. You will need at least 2 buckets or other vessels besides your boil kettle unless you have a HLT.

dougdecinces said:

I'm planning my first parti-gyle next month. It will be a doppelbock/alt. I've run the calculations through and they work out on paper, but this is one of those things that I have been working on so long that I can't quite see the forest for the trees any more. I want to make sure that my math is solid.

The base recipe is follows:
18 lb Munich 10
2 lb Pilsner
1/2 lb Melanoidin
1/4 lb Carafa III

I plan on making 5.25 gallons of Doppelbock and 3.25 gallons of alt. Assuming 70% efficiency, that gives me 523 gravity points to work with. I will extract approximately six gallons of wort each with both the first and second runnings. I plan on taking two gallons from the second runnings and adding them to the doppelbock; then I will do a very long boil to get down to the proper final volume. The alt will get a regular 60 minute boil.

I'm getting a OG of 1.068 for the doppelbock and 1.051 for the alt. But just looking at that, the math does not seem right. Please someone confirm this for me!

Click to expand...

here's a good read on the math and how to estimate partial runoff of a volume of the batch
http://www.brewingtechniques.com/library/backissues/issue2.2/mosher.html

OLDBREW, I saw that article the other day and did find it informative. However, it is also the article that misled me slighty, because I didn't connect the dots about the volumes he was using (or hence, the grist ratios). It seems to me his numbers and charts are only accurate as long as your first runnings are 1/3 of your total running, assuming you double batch sparge.

"For a one-third/two-thirds split, I have found that approximately half of the extract from the malt ends up in first third of the mash runoff, and the other half ends up in the last two-thirds. Because the volume of the first portion is half that of the second portion and has the same amount of sugars, it will be roughly twice as strong."

So, as long as your sparge volume is two-thirds of the total volume, you are good using this. But if you mash thin, you could end up needing to sparge a large amount, possibly leading to over-sparging or exceeding the volume of your mash tun.

OLDBREW said:

here's a good read on the math and how to estimate partial runoff of a volume of the batch
http://www.brewingtechniques.com/library/backissues/issue2.2/mosher.html

Click to expand...

That's what I've been using. I used Mosher's stats saying that 58% of the sugars are extracted in the first runnings and 42% in the second to come up with my figures. But I did the math again, and it's actually 1.068/1.044, which is still more than fine for what I need. I have a can of LME in the fridge that I need to use anyways, so it will go to up the gravity of the doppelbock.

I've used those tables before, on the 50/50 split, my system worked a bit differently. I got about 50% in the first run and 25% for the second beer. I now work up my partigyles in this fashion and get pretty close. They are good approximations, but those efficiencies depend more on you. Also, you can mix and match in your running's to get where you want if need be.

Carter5112 said:

On second thought, after review some info on conversion efficiency based on mash thickness found here (http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Conversion_efficiency) I think we may be significantly off based on your mash thickness.

If you are doughing-in with about 8.5 gallons of water to yield you 6 gallons of first runnings, then that would give you about 1.65 QT/LB. According to this, you'd be getting more around 1.075 @ 6 gallons for your first runnings. That would not leave you much sugars for a 6 gallon batch sparge.

Sorry, someone with more experience will have to chime in here!

Click to expand...

Okay, I've changed things up slightly. I have upped the amount of grains from 20.25 lbs to 23 pounds. I will mash in with about 8 gallons and my mash ratio will go down to about 1.39 (from 1.72 before). I will extract approximately 5 gallons from my mash. I will sparge with 10 gallons to yield 7 gallons of sparge runnings (I would do more, but that's the most my system will allow). This should help with efficiency--especially with the sparge--and I can just add three gallons of the sparge runnings back to the mash runnings instead of the original two.

I made a fancy spreadsheet showing all this, if that will help.