Boiling a short volume and then liquoring back - IBU & Hops

[ScottM]

Ok so I'm trying to work out how much hops I need to brew my German pils.

After reading around a few recipes I've come to the conclusion that the IBUs I should be aiming for is 37.

First of all, does that sound about right for a German Lager? I'm looking for it to be relatively hoppy, similar to Grolsch.

Next..... I'm not going to be boiling the entire batch, I'll be limited to a water volume of around 10L. I've done a bit of digging around and I believe I'm right in saying that I don't take the entire volume into account when working out the IBUs, as only the water itself will take on the acids from the hops. The volume increase due to the sugars should be discounted as this is basically taking up space that the hops won't have any effect on. Is this correct?

Lastly, I need to work out the correct hop addition to end up with a final volume IBU level of 37. Given that I'm boiling only approx 10L rather than the whole 23L batch I understand that I need to increase the hops at the various levels so that when I increase the volume to 23L. With that in mind does the following sound correct...

Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

The above seems logical to me but as we all know, certain things don't quite scale the way they do in an equation so I just want to make sure I'm doing the right thing. Will a boil volume of 10L with IBUs of 85.1 end up having IBUs of 37 when liquored back to 23L?

Thanks :)

 

[ScottM]

Friday night brewers bump

 

[Good Ed]

I wish I could help you Scott, but it seems a bit extreem to liquor back that much, but you're probably correct

 

[ScottM]

I wish I could help you Scott, but it seems a bit extreem to liquor back that much, but you're probably correct

I can't help it unfortunately, my largest pot is 15L.

I'm pretty sure the calculation is correct, or thereabouts, it's just a bit daunting when you see the increase

 

[Good Ed]

I'd just go for it, I'm sure it'll turn out good

 

[dzlater]

Ok so I'm trying to work out how much hops I need to brew my German pils.

After reading around a few recipes I've come to the conclusion that the IBUs I should be aiming for is 37.

First of all, does that sound about right for a German Lager? I'm looking for it to be relatively hoppy, similar to Grolsch.

Next..... I'm not going to be boiling the entire batch, I'll be limited to a water volume of around 10L. I've done a bit of digging around and I believe I'm right in saying that I don't take the entire volume into account when working out the IBUs, as only the water itself will take on the acids from the hops. The volume increase due to the sugars should be discounted as this is basically taking up space that the hops won't have any effect on. Is this correct?

Lastly, I need to work out the correct hop addition to end up with a final volume IBU level of 37. Given that I'm boiling only approx 10L rather than the whole 23L batch I understand that I need to increase the hops at the various levels so that when I increase the volume to 23L. With that in mind does the following sound correct...

Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

The above seems logical to me but as we all know, certain things don't quite scale the way they do in an equation so I just want to make sure I'm doing the right thing. Will a boil volume of 10L with IBUs of 85.1 end up having IBUs of 37 when liquored back to 23L?

Thanks :)

It works like that for gravity points, but I pretty sure it doesn't work that way with hops.
In "Designing Great Beers" there is a chart that gives a multiplier for hop additions in a concentrated boil.
Boil Vol: Fermentor Vol.
For 36 ibu's
1:1 = 1.14
4:5 = 1.17
3.5:5 = 1.20
2.5:5 = 1.28
If I do the math correctly you would only have to increase your hops by a factor of 1.29.
So just figure out how much hops you need for 37 ibu's in a 23L batch, and multiply the bittering additions by 1.29. Or basically just add 25% more hops.
I have few recipe books that have partial boil recipes and they also say to use 25% less when doing a full wort boil.

Hope this helps.
Dan

 

[ScottM]

Ok so I'm trying to work out how much hops I need to brew my German pils.

After reading around a few recipes I've come to the conclusion that the IBUs I should be aiming for is 37.

First of all, does that sound about right for a German Lager? I'm looking for it to be relatively hoppy, similar to Grolsch.

Next..... I'm not going to be boiling the entire batch, I'll be limited to a water volume of around 10L. I've done a bit of digging around and I believe I'm right in saying that I don't take the entire volume into account when working out the IBUs, as only the water itself will take on the acids from the hops. The volume increase due to the sugars should be discounted as this is basically taking up space that the hops won't have any effect on. Is this correct?

Lastly, I need to work out the correct hop addition to end up with a final volume IBU level of 37. Given that I'm boiling only approx 10L rather than the whole 23L batch I understand that I need to increase the hops at the various levels so that when I increase the volume to 23L. With that in mind does the following sound correct...

Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

The above seems logical to me but as we all know, certain things don't quite scale the way they do in an equation so I just want to make sure I'm doing the right thing. Will a boil volume of 10L with IBUs of 85.1 end up having IBUs of 37 when liquored back to 23L?

Thanks :)

It works like that for gravity points, but I pretty sure it doesn't work that way with hops.
In "Designing Great Beers" there is a chart that gives a multiplier for hop additions in a concentrated boil.
Boil Vol: Fermentor Vol.
For 36 ibu's
1:1 = 1.14
4:5 = 1.17
3.5:5 = 1.20
2.5:5 = 1.28
If I do the math correctly you would only have to increase your hops by a factor of 1.22.
So just figure out how much hops you need for 37 ibu's in a 23L batch, and multiply the bittering additions by 1.22. Or basically just add 25% more hops.
Hope this helps.
Dan

Ok that sounds good, I'll go for that.

I can only imagine it'll be a little safer anyway, as surely a bit less hops is better than too much

Based on my maths I would have been using 107g of hops.
Based on the 25% increase I would be using 78g of hops.

It's a bit of a pain that there's no actual way to know if what I'm doing is right. If it tastes right though, it's all gravy :thumb:

 

[ScottM]

Having read around there are different opinions on it but the general consensus is that any difference made will be a lot less than my calculation. Some people believe there is no difference and some people reckon 10-15 depending on boil volume.

Given that I want a fairly hoppy lager I'm happy to over-estimate by a little so I'll go with a 20% increase in hops.

Really glad I asked now

 

[Good Ed]

Also follow the rule that if in doubt add more hops :)

 

[Brycey]

I have the same problem,my biggest pot is also 15l and i don't fancy splashing out on lots more stuff so i'm looking at trying to do some extracts with 10l boil volumes.

Pittsy posted a heffweizen extract recipe that called for 25g then 15g of hops and i basically asked the same question and he suggested using half the amounts again.

I will follow your posts with intrest as we're trying to achieve the same thing. :

B

 

[dzlater]

Ok so I'm trying to work out how much hops I need to brew my German pils.

After reading around a few recipes I've come to the conclusion that the IBUs I should be aiming for is 37.

First of all, does that sound about right for a German Lager? I'm looking for it to be relatively hoppy, similar to Grolsch.

Next..... I'm not going to be boiling the entire batch, I'll be limited to a water volume of around 10L. I've done a bit of digging around and I believe I'm right in saying that I don't take the entire volume into account when working out the IBUs, as only the water itself will take on the acids from the hops. The volume increase due to the sugars should be discounted as this is basically taking up space that the hops won't have any effect on. Is this correct?

Lastly, I need to work out the correct hop addition to end up with a final volume IBU level of 37. Given that I'm boiling only approx 10L rather than the whole 23L batch I understand that I need to increase the hops at the various levels so that when I increase the volume to 23L. With that in mind does the following sound correct...

Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

The above seems logical to me but as we all know, certain things don't quite scale the way they do in an equation so I just want to make sure I'm doing the right thing. Will a boil volume of 10L with IBUs of 85.1 end up having IBUs of 37 when liquored back to 23L?

Thanks :)

It works like that for gravity points, but I pretty sure it doesn't work that way with hops.
In "Designing Great Beers" there is a chart that gives a multiplier for hop additions in a concentrated boil.
Boil Vol: Fermentor Vol.
For 36 ibu's
1:1 = 1.14
4:5 = 1.17
3.5:5 = 1.20
2.5:5 = 1.28
If I do the math correctly you would only have to increase your hops by a factor of 1.29.
So just figure out how much hops you need for 37 ibu's in a 23L batch, and multiply the bittering additions by 1.29. Or basically just add 25% more hops.
I have few recipe books that have partial boil recipes and they also say to use 25% less when doing a full wort boil.

Hope this helps.
Dan

I have been thinking about this.
When you said
Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

That is actually correct,
I was thinking you were going to adjust so the IBU's at the 23L was 85.
So if you were designing the recipe as 10L batch, you were correct in assuming you needed 85 ibus, before you added the rest of the water.
If you were designing the recipe as a 23L batch you would use the 37ibu's and add the 25% for the concentrated boil.
Hope I didn't screw up your beer.

Dan

 

[ScottM]

Ok so I'm trying to work out how much hops I need to brew my German pils.

After reading around a few recipes I've come to the conclusion that the IBUs I should be aiming for is 37.

First of all, does that sound about right for a German Lager? I'm looking for it to be relatively hoppy, similar to Grolsch.

Next..... I'm not going to be boiling the entire batch, I'll be limited to a water volume of around 10L. I've done a bit of digging around and I believe I'm right in saying that I don't take the entire volume into account when working out the IBUs, as only the water itself will take on the acids from the hops. The volume increase due to the sugars should be discounted as this is basically taking up space that the hops won't have any effect on. Is this correct?

Lastly, I need to work out the correct hop addition to end up with a final volume IBU level of 37. Given that I'm boiling only approx 10L rather than the whole 23L batch I understand that I need to increase the hops at the various levels so that when I increase the volume to 23L. With that in mind does the following sound correct...

Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

The above seems logical to me but as we all know, certain things don't quite scale the way they do in an equation so I just want to make sure I'm doing the right thing. Will a boil volume of 10L with IBUs of 85.1 end up having IBUs of 37 when liquored back to 23L?

Thanks :)

It works like that for gravity points, but I pretty sure it doesn't work that way with hops.
In "Designing Great Beers" there is a chart that gives a multiplier for hop additions in a concentrated boil.
Boil Vol: Fermentor Vol.
For 36 ibu's
1:1 = 1.14
4:5 = 1.17
3.5:5 = 1.20
2.5:5 = 1.28
If I do the math correctly you would only have to increase your hops by a factor of 1.29.
So just figure out how much hops you need for 37 ibu's in a 23L batch, and multiply the bittering additions by 1.29. Or basically just add 25% more hops.
I have few recipe books that have partial boil recipes and they also say to use 25% less when doing a full wort boil.

Hope this helps.
Dan

I have been thinking about this.
When you said
Boil IBU = Final IBU*Final Volume/Boil Volume

Boil IBU = 37*23/10
Boil IBU = 85.1

That is actually correct,
I was thinking you were going to adjust so the IBU's at the 23L was 85.
So if you were designing the recipe as 10L batch, you were correct in assuming you needed 85 ibus, before you added the rest of the water.
If you were designing the recipe as a 23L batch you would use the 37ibu's and add the 25% for the concentrated boil.
Hope I didn't screw up your beer.

Dan

The maths is correct and the theory is plausible, but in reality it doesn't work out like that apparently.

Its effectively like instant coffee. If you like 2 tsp of coffee in a mug, how much would you add to half a mug to then "liquor back" to make a full mug? Well, the answer is obviously 2 tsp, if you increased it like the above formula it would look like the following..

Coffee = Final Coffee Strength *Final Volume/Boil Volume
Coffee = 2tsp * 1/0.5
Coffee = 4tsp


Its all down to hop utilisation, and apparently the boil volume makes little difference to the acids extracted.