Amt of water affecting bitterness

In the beginners' area, responding to a post on Scottish Ale, Storunner13 mentioned that more water in the boil would result in more bitterness.

Just wondering - why? How does that work? I'd assumed that the amount of time in the boil would be most important (assuming identical ingredients between compared batches).

That's a new one on me. I suppose the reasoning is that more water implies more dilute wort and more dilute wort dissolves more isomerized bittering principal from the hops.

I think you are referring to the fact that a full wort boil will result in better hop utilization when compared to a thick partial boil. As AJ said, this will allow more isomerization of AA's.

If you read Palmer's Learn to Brew, check out Chapter 5 on Hops. He discusses utilization. Basically, what he boils it down to is that the volume of wort and the gravity of the wort, along with the amount of time you boil the hops go into determining the utilization.

He uses a scale developed by Tinseth to give utilization of hops boiled in a wort of a certain gravity for a certain amount of time. The math he uses is fairly straightforward. You determine the AAU contribution of your hops by multiplying the weight of hops you use by the AA% for the particular variety.

Then you determine the gravity of the wort in your boil (he gives instructions for that as well).

Then you look up the utilization on the Tinseth chart by taking the gravity of your starting boil and comparing it on the chart to the amount of time you intend to boil the hops in that gravity.

Finally, you multiply the AAUs contributed, the utilization and a constant for metric/standard conversion (explanation in the chapter). Then divide it by your final volume (batch size) to get the number of IBUs contributed by each hop.

So the short answer is ajdelange's. You get more utilization (and therefore more IBUs) boiling your hops in a larger, more dilute volume of liquid because, as Palmer states it, "hop utilization decreases with increasing wort gravity".

winvarin said:

If you read Palmer's Learn to Brew, check out Chapter 5 on Hops. He discusses utilization. Basically, what he boils it down to is .....

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Pun not intended but I just caught it and had to laugh a little.

winvarin said:

You get more utilization (and therefore more IBUs) boiling your hops in a larger, more dilute volume of liquid because, as Palmer states it, "hop utilization decreases with increasing wort gravity".

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I've seen several people dispute that statement. Their reasoning was that utilization was decreased by break material in the wort and not by gravity. Since the amount of break material is sometimes (even often) correlated with gravity, it sometimes (even often) gives a good estimate.

SpanishCastleAle said:

I've seen several people dispute that statement. Their reasoning was that utilization was decreased by break material in the wort and not by gravity. Since the amount of break material is sometimes (even often) correlated with gravity, it sometimes (even often) gives a good estimate.

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My experience has borne out, perhaps anecdotally, that the larger kettle volume does increase hop utilization ... or at least perceived bitterness. But I have no scientific evidence to back up what about the larger volume (gravity or amount of break) is contributing to the increased bitterness.

I can't argue it either way. I was merely quoting something from Palmer that seems to back the claim made by a lot of brewers that increasing the volume appears to increase the bitterness extracted from your hops.

Without a very credible case to the contrary, I think most brewers will continue to embrace the "settled" maxim that lower gravity boils increase isomerization.

Alright, alright. I found the credible cases.

My experience has borne out, perhaps anecdotally, that the larger kettle volume does increase hop utilization

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That sounds right. Just look at some commercial brewery recipes scaled for their systems. Then linearly scale them to a 5 gallon batch and you will find it wouldn't be enough hops to provide the stated bitterness.

MachineShopBrewing said:

That sounds right. Just look at some commercial brewery recipes scaled for their systems. Then linearly scale them to a 5 gallon batch and you will find it wouldn't be enough hops to provide the stated bitterness.

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I've read that too, that the big batch recipes don't scale down right. But when I use Tinseth it always gives me a number that seems lower than what I actually get (but I haven't had this tested). IOW, my beers are always more bitter than Tinseth predicts. I've been tweaking the numbers in Tinseth for my use and seem to be getting closer. I get way better utilization with late additions than Tinseth predicts and utilization also seems to be way less influenced by gravity than Tinseth predicts (a good example is that hop-bursted IPAs have turned out WAY more bitter than Tinseth predicts). But that's just my system.

Are you using the charts or his actual equations? I've used his equations (which use an average wort gravity for the boil) and have had pretty good success (in the 10 batches I've brewed so far). Are you using an average boil gravity or final boil gravity? If you use only your FG it would underestimate bitterness. So you would end up with more bitterness than predicted. This wouldn't have much of an effect on your late additions but would definitely affect bittering additions.

ayoungrad said:

Are you using the charts or his actual equations? I've used his equations (which use an average wort gravity for the boil) and have had pretty good success (in the 10 batches I've brewed so far). Are you using an average boil gravity or final boil gravity? If you use only your FG it would underestimate bitterness. So you would end up with more bitterness than predicted. This wouldn't have much of an effect on your late additions but would definitely affect bittering additions.

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I use the actual equations using the average boil gravity.

winvarin said:

If you read Palmer's Learn to Brew, check out Chapter 5 on Hops. He discusses utilization. Basically, what he boils it down to is that the volume of wort and the gravity of the wort, along with the amount of time you boil the hops go into determining the utilization.

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Palmer also redacted that after seeing science to the contrary. Many have done experiments since ( Basic Brewing Radio comes to mind who had partial and full boil beers lab tested for IBU ), and there is no direct correlation between hop utilization and wort gravity. What is true is break material can draw iso-alpha acids out of solution. So, worts with significant break can experience some IBU loss.

Hey Spanish are you checking your finished beer pH? This would affect percieved bitterness also.

jkarp said:

Palmer also redacted that after seeing science to the contrary. Many have done experiments since ( Basic Brewing Radio comes to mind who had partial and full boil beers lab tested for IBU ), and there is no direct correlation between hop utilization and wort gravity. What is true is break material can draw iso-alpha acids out of solution. So, worts with significant break can experience some IBU loss.

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Concentrated wort gravities over 1.050 do have some effect on hop utilization and IBU calculations. See chapter 9 of Designing Great Beers for the full story.

MachineShopBrewing said:

Hey Spanish are you checking your finished beer pH? This would affect percieved bitterness also.

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Yes I check it with a meter.