more hops?

[DanOmite]

I have scaled back my batch size to 3-gallons and I now boil only 1.5 gallons. Thus, the boil is a lot denser. Do I need to add more hops to get the same bittering I would get from boiling 3-gallons?

Beer tools is kind of confusing me, because it indicates that I will more hop utilization from a smaller boil. I thought it was the other way around. If so, is there some rule of thumb / conversion factor I can multiply my current hop amounts by to make up for this small batch effect?

 

[Shrewd_Alchemist]

All I read was the title of this thread - the answer is always

I would think that it's probably going to be pretty close either way. What you are doing is similar to boiling 2.5 gallons for a 5 gallon batch. I did extract for a while and now that I'm doing all grain, I don't really notice a drastic increase in utilization from my hops. Brew it according to the recipe, it'll probably turn out just fine. If not, do it again and add more hops! You always need to have one on deck

 

[SumnerH]

I did extract for a while and now that I'm doing all grain, I don't really notice a drastic increase in utilization from my hops. Brew it according to the recipe

Neither did I. Turns out that's because hops utilization is independent of boil gravity---something brewing software almost universally gets wrong, largely because up until about 2 years ago most of the big names in home brewing had it wrong too.

Listen to John Palmer's "What is an IBU, Really?" from 20 March 2008 where he talks about it (including apologizing for getting this wrong in the most recent edition of How to Brew):
http://www.basicbrewing.com/index.php?page=basic-brewing-radio-2008

Or the episode where they brew the same recipe as a full boil, partial boil, and partial boil with late extract additions, then measure the IBUs of the 3 beers. Hop utilization is identical. March 4, 2010 - BYO-BBR Experiment III:
http://www.basicbrewing.com/index.php?page=radio

The commercial brewing literature is littered with this information, going back decades. e.g. the American Society of Brewing Chemists in 1989:
http://www.asbcnet.org/journal/abstracts/backissues/47-14.htm says
"In the range 10.5-13.5° P, no relationship between hop utilization and original gravity was found. "

More discussion here:
https://www.homebrewtalk.com/f128/estimating-bitterness-algorithms-state-art-109681/
https://www.homebrewtalk.com/f14/hop-utilization-178668/

 

[mojotele]

Based off stuff I learned from the sources SumnerH has cited, I'd think you need less than half of the hops in a 1.5 gallon batch than you'd need for the 3 gallon batch.

My reasoning is that you'd need less extract or grain to reach the same gravity, and would thus have less break material. Since the break material serves as nucleation sites for the isoalphas and oxidized betas (if I understood Palmer right), that means better hop utilization. Since you're cutting your volume in half, you'd need at most half the amount of hops. But since you'll have less break material, you can use slightly less than half.

Or am I missing something? I may be wrong about the "slightly less than half" portion as it may depend on both break material and wort volume, but it seems you'd use at most half the hops you'd normally use. Any brewing software will make that change when you scale a recipe down by half. Please correct me.

 

[SumnerH]

Based off stuff I learned from the sources SumnerH has cited, I'd think you need less than half of the hops in a 1.5 gallon batch than you'd need for the 3 gallon batch.

My reasoning is that you'd need less extract or grain to reach the same gravity, and would thus have less break material. Since the break material serves as nucleation sites for the isoalphas and oxidized betas (if I understood Palmer right), that means better hop utilization.

You're talking about doing a 1.5 gallon batch at some gravity (say, 1.040) vs. a 3 gallon batch at the same gravity? Basically, brewing different quantities of total beer. That's not what I understood OP was doing, but to address that scenario:

(long boring response; feel free to skip):

First, it's adsorption, not nucleation--nucleation refers to a thermodynamic phase change. If you're talking about beer, pouring salt into a carbonated beer is a good example--it provides places for a dissolved chemical to undergo a phase change, form a bunch of bubbles, and float away. Adsorption is when molecules of one chemical stick to another; in our case, isoalphas adsorb to break material, which then precipitates out (carrying the isoalphas with it).

With less break material you'll lose less isoalphas, but you have less water so the _concentration_ of break material would be the same in a 1.040 1.5 gallon batch as in a 1.040 3 gallon batch--so though you'd lose less total isoalphas, you'd lose about the same proportion.

In practice with extract, the break material is minimal enough that it's not really worth considering (see BBR's IBU measurements, for instance).

Since you're cutting your volume in half, you'd need at most half the amount of hops. But since you'll have less break material, you can use slightly less than half.

Or am I missing something?

He's only boiling 1.5 gallons but he's still making 3-gallon batch (topping off with water). So he's boiling 50% of the batch size.

Previously he was boiling 3 gallons; he didn't say how big his batch was, but 3-gallons represents a "scaled back" size. Assuming he was brewing typical 5 gallon batches before, then he was boiling 60% of the batch size.

So, in theory, he has slightly more concentrated break material in the boil than he did before, and would need slightly more hops per gallon than before--but going from 50% to 60% of final volume is a very modest change in boil density.

I'd go with the same hops per gallon before (basically, 3/5 of the total hops if he was doing 5 gallon batches and is now doing 3 gallon batchs--if a recipe needed 2 oz of a hop for 5 gallons, I'd go with 1.2 oz for 3 gallons.), personally.

 

[mojotele]

SumnerH, thanks for clearing that up for me. I clearly misunderstood the OP. Now that I read it when fully awake, it is clear he is just doing a denser boil rather than a smaller batch.

Also, thanks for explaining the difference between nucleation and adsorption. I've never heard the latter term, and it's always fun to learn something new.

I figured the concentration of the break material was what mattered after I made that post, but I hoped that you'd come back and tell me for sure. Thanks again!