# Boil Gravity For Best Hop Utilisations.



## br33zy (30/1/09)

In [topic="29496"]this post[/topic], Butters (whose posts are always very very helpful) mentioned the following when discussing the amount of LDM to be included in partial boils in order to get a good (or expected) hop utilisation:



buttersd70 said:


> A good rule of thumb for the boil is to add 100g of ldm per L of water (which will give a boil gravity of 1040), and for short boils like this, 2-3L would be sufficient. ...



We are brewing partials at the moment. Our current recipe, an SNPA clone, boils the wrt from the steeped crystal, adding hops according to the schedule at 60mins, 30mins, 10mins and flameout. We brew with DME and have (to date) been pretty random about when we actually add the DME to the boil. Some in early, some in late - details not recorded.

Butters, would you mind elaborating a little on what we should be aiming for in terms of boil gravity, and how that effects hop utilisation? Would we do any harm by putting all the DME in at the start of the boil? Or alternatively just before the end of the boil?

If you have any links you can refer me to I'm happy to go and do the reading

Cheers

Breezy

P.S. Shit its hot.


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## stm (30/1/09)

Generally speaking, the lower the gravity the better the hop utilisation. Try playing with some numbers here:

http://www.realbeer.com/hops/bcalc_js.html


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## buttersd70 (30/1/09)

No shit its hot. <_< 

Basically, the higher the boil gravity, the lower the utilisation will be on the hops. (less bitterness extracted). But to utilise properly, and for flavour development, there needs to be some malt present. The _actual _gravity isn't a crucial thing, it doesn't need to be 1040, as long as you _know _what it is, because that will be used to calculate the hopping. The reason I reccomended 1040 as a gravity is a matter of compromise, convenience, and repeatability. It's very easy to get a 1040 gravity with 100g/L of ldme, which makes things very convenient. The gravity is also high enough for flavour development, and also low enough for decent utilisation.....1030, as an example, would work just as well, in fact you would get better utilisation....but then you need to work out how much ldm to give it. (it's about 80g/L, btw.  ) 

Adding all the malt at the start will do 2 things...firstly, it will make a really high boil gravity, and lower the utilisation dramatically. So you'd need a lot more hops. It would also darken significantly during the boil, because of it being so concentrated.


Hope that helps


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## ianh (30/1/09)

Hi tis hot

Agree with Buttersd70 on the boil gravity, however when doing small boils you should also take into account the Hop Concentration Factor.

The solubility of the hop iso-alpha acids is limited and with small boil volumes the HCF becomes important. The equation was developed by Mark Garetz.

HCF = 1+ ((Final Vol / Boil Vol) * Desired IBU) / 260

have a play with the numbers and see what a difference it can make. In some cases going from 2 litres to 8 litres Boil Volume could make up to 50% difference in the bitterness level.

I am trying to put all the numbers into a spreadsheet for us Kit & Extract guys to use. Once I have it in reasonable shape I will post a copy on the forum.

cheers

Ian


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## buttersd70 (30/1/09)

Ian is right in what he's saying, and for an extract or partial that has all hopping done by yourself, then volume sarts to become a factor if using Garetz's formulation...but in the context of the original thread, it's k&k brewing with a bit of added malt...so your talking less than 5IBU in a short boil required to rebalance sweetness...the difference it would make is sfa. Calculate using Tinseth or Rager, and you get completely different results anyway. So IBU calculations are subjective, depending on the formulation used for the calculation.


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## cdbrown (30/1/09)

I'm having trouble getting the correct IBU's out of beersmith due to boil volumes and the amount of ldme in the boil.

Putting 250g LDME and 20g challenger (AA7.5%) in 2.5L boil volume for a boil time of 30min - gives 13IBU in 23L
Change the boil size only to 5L and IBU goes up to 15.3. Should that be the case as now the utilisation is worse with the lower SG?

Butters which bitterness formula do you use in beersmith?


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## buttersd70 (30/1/09)

cdbrown said:


> Should that be the case as now the utilisation is worse with the lower SG?
> 
> Butters which bitterness formula do you use in beersmith?



Utilisation is _better _with lower sg.  

Personally I use Tinseth. But having said that, my boils are full volume now that I brew AG...and when I brewed extract, it was a high volume (15L, cos my earn could fit it in easy.) boil, anyway, which minimises any differences.

edit...software such as beersmith should account for any utilisation issues in lower volume boiling anyway, because unlike manual calculations, they have all the info input into them as to what is in the boil, it's volume, and the final volume. So it's really a non issue, imo, unless working out the hopping using formulation manually.


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## cdbrown (30/1/09)

Sorry to hijack

So based on all the bits of advice, the bigger the boil generally the more IBU's extracted from the same amount of hops. Going from 12L down to 3L means the IBU in a 23L batch changes from 30 down to 7. I can only do 3L boils at the moment as the 5L pot is my restriction. Not found an 18L pot in any of the shops, only 10L for about $50. To get the IBU's needed from a small boil I'd need to crank up the amount of hops - yes??


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## Gavo (30/1/09)

cdbrown said:


> Sorry to hijack
> 
> Going from 12L down to 3L means the IBU in a 23L batch changes from 30 down to 7.



Almost a topic for another thread.

When you take the 12lt boil down to 3lt what is pre-boil gravity? Are you using BeerSmith to work it out?
Have you checked the pre-boil gravity in the brewsheet? 30IBU down to 7IBU is a large difference.

Cheers
Gavo.


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## buttersd70 (30/1/09)

cd
I think the error you're making is that when you downsize the boil volume, you're leaving the malt amount the same, which causes the boil gravity to shift, and that effects utilisation more than the size of the boil itself....

OK, to get an idea and a visualisation of what is going on, set up a recipe in Beersmith with a 23L final volume. Set the recipe type to "partial mash" instead of extract. Set the boil volume to 10L. Add enough dry malt to give an OG of 1040, but split it to have 1kg in the boil, and the rest "add after boil". Then click the "brewhouse efficiency' button, and check the "estOG into Boiler". If it's not 1040, juggle the malt amounts until it is (it should be close). Then hop it to 20IBU. Then, change the boil size to 3L, but reduce the malt in the boil to 300g (and increase the other malt to maintain 1040 overall). Click on 'brewhouse efficiency' again to check the "est OG to Boiler' is at 1040, and adjust the malts accordingly....Once you have the Boil grav at 1040, adn the overall grav at 1040, have a look at what difference there is in the IBU......this is what you get.

Recipe: 5L boil BG 1040
Brewer: 
Asst Brewer: 
Style: Altbier
TYPE: Partial Mash
Taste: (35.0) Boil gravity is 1040.

Recipe Specifications
--------------------------
Batch Size: 23.00 L 
Boil Size: 5.00 L
Estimated OG: 1.040 SG
Estimated Color: 7.2 EBC
Estimated IBU: 19.9 IBU
Brewhouse Efficiency: 75.0 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount Item Type % or IBU 
1.95 kg Extra Light Dry Extract after boil (5.9 EBCDry Extract 78.0 % 
0.55 kg Light Dry Extract (15.8 EBC) Dry Extract 22.0 % 
26.00 gm Cluster [7.00%] (60 min) Hops 19.9 IBU 


--------------------------------------------------------------------------------------
BeerSmith Recipe Printout - http://www.beersmith.com
Recipe: 10L boil BG 1040
Brewer: 
Asst Brewer: 
Style: Altbier
TYPE: Partial Mash
Taste: (35.0) Boil gravity is 1040.

Recipe Specifications
--------------------------
Batch Size: 23.00 L 
Boil Size: 10.00 L
Estimated OG: 1.040 SG
Estimated Color: 8.5 EBC
Estimated IBU: 19.9 IBU
Brewhouse Efficiency: 75.0 %
Boil Time: 60 Minutes

Ingredients:
------------
Amount Item Type % or IBU 
1.40 kg Extra Light Dry Extract after boil (5.9 EBCDry Extract 56.0 % 
1.10 kg Light Dry Extract (15.8 EBC) Dry Extract 44.0 % 
26.00 gm Cluster [7.00%] (60 min) Hops 19.9 IBU 

So whilst the volumes changed for the boil, keeping the gravity the same leaves the IBU the same, at least when using tinseth. Changing to a differant hop formula, such as garetz, gives 16.1 IBU for both, and Rager gives 23.7IBU for both. Theoretically, the smaller boil will give you a lower Hop Utilisation Factor. If you were to calculate it manually, adn account for that (instead of leaving it at beersmiths default 100%), you would get a differant result....however, for _practical _purposes, just leave it as it is......because even in a full boil system, there is no way of knowing what your _specific _HUF is without actually having lab tests done on a sample.....so an assumption _has _to be made. So the IBU that you are projecting from your system may not be as bitter, relatively speaking, on the palate as the same IBU from someone elses system. But the differences are purely academic.

So short version is, rdwhahb, adjust your boil gravities when up/down sizing the boil volumes, and bitter it to a level that is right for _your _tastes, using the same _method _consistantly. If the same method is used, then it can be adjusted comparatively  .

Hope that makes sense.

Edit...sorry for going kinda OT, breezy.
Edit V2....I said to set it at partial....that opens up the 'efficiency' button, which allows you to quickly and easily check the BG without having to come out of the recipe to check the brewsheet.


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## unterberg (30/1/09)

buttersd70 said:


> So short version is, rdwhahb, adjust your boil gravities when up/down sizing the boil volumes, and bitter it to a level that is right for _your _tastes, using the same _method _consistantly. If the same method is used, then it can be adjusted comparatively  .
> 
> Hope that makes sense.



Thats the way to go. I am doing smaller volumes at the moment too. Nothing wrong with that I reckon.
And my understanding was that the boil volume shouldnt change the bittering achieve by a set amount of hops as long as you have the same gravity in your boil. 
Glad butters agrees


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## ianh (30/1/09)

cdbrown said:


> I'm having trouble getting the correct IBU's out of beersmith due to boil volumes and the amount of ldme in the boil.
> 
> Putting 250g LDME and 20g challenger (AA7.5%) in 2.5L boil volume for a boil time of 30min - gives 13IBU in 23L
> Change the boil size only to 5L and IBU goes up to 15.3.



If you leave the Boil SG (1.040) the same irrespective of volume size and increase the volume size you will get and increase in hop utilization and in IBU levels especially when doing small Boil Volumes. This is the effect of the HCF factor.

This is just one way of calculating the hop utilization factor. But because Kit & Extract brewers tend too boil smaller volumes than AG brewers it becomes important

Ian


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## dr K (30/1/09)

IBU's are directly related to Volume of Wort, AAU of the hop(s) and mass of the hop(s) and utilisation of the hop(s). The Volume/Mass/AAU made an old back of envelope formula for HBU, Home Brew Unit.
There are much more complex calculations available, personally I use the Tinseth (I know it makes sense), Tinseth uses "Bigness Factor" which is derived from observed variations in utilization where only the wort gravity varied. The Tinseth method calculates utilisation from time and gravity, the longer the time the greater the utilisation (up to a terminal utilisation), the higher the gravity the lower the utilisation. The calculations are done in Plato, there is not a linear relationship twixt Plato and SG (those crazy ancient greeks).
Anyone who plays around with comparing the four methods (HBU, Rager, Tinseth and Garetz) will notice a signifcant variation in calculated IBU which begs a pretty big question, does it not ?

K


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## Gavo (30/1/09)

Yep that's what I am thinking Butters. Just not as in as many words. Beersmith assumes a little in thinking that you understand the relationship between pre-boil gravity and hop utilization. It's not until you take notice of the brew-sheet and play with splitting the extract amounts changing the pre-boil gravity that you notice this difference.

I reckon this is still OT as it relates to boil gravity and hop utilization.

Cheers
Gavo.


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## buttersd70 (30/1/09)

dr K said:


> Anyone who plays around with comparing the four methods (HBU, Rager, Tinseth and Garetz) will notice a signifcant variation in calculated IBU which begs a pretty big question, does it not ?



As K has pointed out in his astute manner, the variations in the formulae pose a big question....that being, which is right? (correct me if I'm wrong, or if I've misunderstood you, please K). IMO, _none _of them are right, and at the same time, _all _of them are right. A quandry, indeed...especially for a "number nut" such as myself. Which all leads back to.....pick _one _formula, and _consistantly _use it, and get _consistant _results from it.....I'm happy by and large to let beersmith make certain assumptions and calculations for me....but use those same assumptions and calculations on a consistant basis, to achieve consistant results.


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## br33zy (31/1/09)

Thanks Butters and all for a great discussion. We're just about to start brewing with much larger equipment (98l - woohoo!), sticking with a partial recipe for the moment (SNPA clone which is tasting gorgeous...and the dramatic increase in boil volume has had me wondering for the past week or so. This thread (and the one which it originated from) have answered a lot of the questions.



buttersd70 said:


> .....pick _one _formula, and _consistantly _use it, and get _consistant _results from it.....



Consistency. Consistency. Consistency. There is the Wisdom!

When we brew the next batch on Tuesday night I'll be recording boil gravity and volume, and DME additions for the first time (we always had more urgent things to worry about with two small brim-full boiling pots teetering on camp stoves with the earlier batches) - so it will be a first chance for us to try and get some accurate IBU numbers, and then start equating those numbers with our taste impression.

Cheers

Breezy

P.S. Might be time to abandon the trusty Calculating Bitch (home cooked brewing spreadsheet) for a Beersmith download too...


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## ford-ute (31/1/09)

wow good question brezzy. possible need a new thread but butters mentioned earlier that 1.040 was enough for flavour development 

so I was wondering if you just boiled you hops in straight water and used less you could get the same IBU's but what would it do for flavour

A mate of mine did it with an exstract and said it tasted fine really bitter but still good


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## buttersd70 (31/1/09)

Boiling in water will give bitterness, no question. Ive done a correction for an underhopped beer in this method, as well as making samples up for hop tastings. You do get flavour from it, but many people consider that it is a harsher flavour....I don't know the science behind it, but I tend to agree (but my opinion isn't set in stone on this).

BasicBrewing did water boil experiments ages ago, and it was in one of their podcasts...would have been maybe late 07?. It was in the video podcasts on basicbrewing.com, if you can find it.


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