Converting AHS mini mash from partial to full boil

[KG-Brew]

Just got my AHS Rogue Dead Guy Clone mini-mash and found out it is a partial boil. I have all the equipment so I would like to do a full boil. I will follow the directions for steeping/mashing & sparging...but just add additional water for the boil. From what I understand the only thing I need to change is the hop additions as a full boil would result in much higher IBU's for the same hop additions. Here is the recipe, thanks for the help.

Recipe Instructions from AHS:
Mash 2 gal @ 155 grain: 1# Pale, 1# Munich, 3/4# Carastan, 3/4# Caramunich for 30 mins. Then sparge with 1 qt/1b of grain. Then add 1 gal of water, bring to boil, add 7# Amber LME. Hops: 1.5oz Perle (60 min), 0.5oz Saaz (60 min), 0.5oz Saaz (15 min).

When I run the calc's in brewer's friend (with boil volume of 4.5) this results in an IBU of 49. This is about right because RDG is listed at 40 and the "Can You Brew It" recipe came up with an IBU of 49, so its in the nighborhood. When I up my boil volume to 7 gal, it raises IBU to 62 due to the hop utlization change with the extra volume, I get that...my question can I just adjust my hops to get back down to 49 or so and do a full boil with no issues? I wanted to make sure I wasnt missing something, I am, afterall, looking for a Rogue Dead Guy clone. Thanks for the help everyone.

 

[freisste]

Adjust your additions down. I would assume you want to adjust them all about the same ratio to keep the balance right, but balance may have already been taken into account for dry hopping, if any. What I mean is, you would dry hop after the volume was increased...

 

[KG-Brew]

Ok thanks...that was my plan. To adjust my hop additons down to maintain a 40-49 IBU. I wasnt planning to dry hop though.

 

[Yooper]

Ok thanks...that was my plan. To adjust my hop additons down to maintain a 40-49 IBU. I wasnt planning to dry hop though.

I wouldn't adjust at all, but if you want to that's fine. All you reduce is the bittering (60 minute) addition. You could go with 1- 1.25 ounces of perle instead of 1.5 ounces if you wanted, or just leave out the 60 minute saaz and it should reduce your IBUs just fine.

I think my clone is spot on, but I haven't ever tried AHS recipe/version so I don't know how close theirs is.

 

[KG-Brew]

Thanks Yooper! When you say you wouldn't adjust at all, that becaue you want a 65-70 IBU dead guy clone? My point for the clone was to get it back closer to the 40-49 that it acutally is. Just curious if I am missing some reason you wouldn't adjust. Thanks

 

[Yooper]

Thanks Yooper! When you say you wouldn't adjust at all, that becaue you want a 65-70 IBU dead guy clone? My point for the clone was to get it back closer to the 40-49 that it acutally is. Just curious if I am missing some reason you wouldn't adjust. Thanks

No. It's because I don't believe the software that bases IBUs on wort gravity and volume.

It's been proven that IBUs are NOT dependent on wort gravity, although break material can impact it and "pull" some of the IBUs out of the wort.

There have been experiments done (notably, recently by Basic Brewing Radio), that have shown no changes in IBUs in a full boil, late extract addition, or a partial boil.

The only exception I know of is for a very high IBU beer. That's because of dilution, though, not wort gravity. There is a maximum of hops oils that can isomerize in solution before the wort is saturated with the oils. That maximum is widely believed to be 100 IBUs or so. So, if you're hoping to make a 75 IBU beer with a partial boil, that's impossible. The reason is simple- say you have 2.5 gallons of wort with 100 IBUs. You add 2.5 gallons of water (0 IBUs) and then the grand total is 50 IBUs. So if there are differences in partial boils vs full boils, that is the reason and not because of the wort gravity. I hope that makes sense.

Calculating IBUs is a guestimate at best. Even Pliny the Elder, which calculates out to 200+ IBUs has been tested in a lab, and actually has something like 80 actual IBUs!