Scaling Hops To Match Biab Sparge

[Truman42]

Also worth considering that your final volume, boil vigour and your boil gravity are what will affect hop utilisation the most so the calcs probably won't be far off.

Generally Im well over my OG at EOB. Last nights brew should have had an EOB SG of 1.054 but I ended up with an SG of 1.062. Obviously due to sparging and the great job my missus does of stirring the sparge and exracting maximum sugars..

I suppose what I should be doing is checking my SG at start of boil after my first sparge and add boiled water instead to compensate for evaporation loss as Im obviously getting better efficiency than the 75% I set in brewmate due to the sparges.

My current practice is to just add water to the cube at a calculated dilution rate to drop the SG to the required figure. But either way I do it I was concerned that my hop additions should be increased to compensate for this.

The maxi biab method I do suits my equipment. I can boil in an 18 litre urn and still get 18 litres in my cube after dilution etc.

 

[Vanoontour]

Surely to keep it simple, the evaporation from your boil increases your gravity so dilute at the end as its going in your cube? Keeps all your calcs simple that way, just set and forget.

Thats what I do and I'm always above OG at the end of the boil.

 

[Truman42]

Surely to keep it simple, the evaporation from your boil increases your gravity so dilute at the end as its going in your cube? Keeps all your calcs simple that way, just set and forget.

Thats what I do and I'm always above OG at the end of the boil.

Yeh well now that I know my system better thats the method I will use from now on. Sparge only once and use boiled water to top up during the boil
to bring the Sg down. But how much do I increase my hops by to compensate?

 

[Vanoontour]

I sparge once and get 18l into the 19l pot, boil it and top up right at the end as it goes into the cube. That way I don't need to worry about different hop addition amounts dependant on how much evap there was.

When you get your evap, along with the increase in gravity, my understanding is you also increase your IBU's and colour, so diluting at the end only brings it back to what it should be. But happy to be corrected on this as I am new as well.

 

[stux]

If you were being pedantic

The end of boil OG should be equal to

(Start of boil gravity x start of boil volume + sparge gravity x sparge volume) / end of boil volume

The hop additions should be calculated based on the average gravity during the addition of the hop and average volume. This is done using ratios. But is a bit trickier

As far as I know no software does this properly. My maxi-biab calc does handle water additions during the boil, but not sparge additions, so it will miss a little bit of gravity. My ce calc does handle the sparge addition but not hop additions

Anyway, if you adjust your software's evaporation to zero or whatever gets you to your EOB volume given your SOB volume, then that should mostly compensate for the liquid addition. What it won't compensate for is the sparge sugars, but that effect should be minimal anyway.

 

[Truman42]

I sparge once and get 18l into the 19l pot, boil it and top up right at the end as it goes into the cube. That way I don't need to worry about different hop addition amounts dependant on how much evap there was.

When you get your evap, along with the increase in gravity, my understanding is you also increase your IBU's and colour, so diluting at the end only brings it back to what it should be. But happy to be corrected on this as I am new as well.

I sparge twice so I cover evap loss and..can add water to the cube as my EOB Sg is usually 10 points or so higher than it should be.
I usually get 15-16 litres into my cube after kettle trub loss and then add a further 1-2 litres of water to bring it up to 18 litres.

It works for me and I get the max volume I can per brew.

Still trying to get my head around it all but would it be right in saying if I dilute back to the recipes original OG before pitching then my recipes hop additions should be right?

From what Im understanding from the replies, hop additions are affected more by a change in gravity rather than volumes, especially if I end up getting my recipe volume through sparging and water additions anyway?

Sorry if Im not grasping what your saying. Just having trouble getting my head around it all, but do appreciate the help.

 

[stux]

I sparge twice so I cover evap loss and..can add water to the cube as my EOB Sg is usually 10 points or so higher than it should be.
I usually get 15-16 litres into my cube after kettle trub loss and then add a further 1-2 litres of water to bring it up to 18 litres.

It works for me and I get the max volume I can per brew.

Still trying to get my head around it all but would it be right in saying if I dilute back to the recipes original OG before pitching then my recipes hop additions should be right?

From what Im understanding from the replies, hop additions are affected more by a change in gravity rather than volumes, especially if I end up getting my recipe volume through sparging and water additions anyway?

Sorry if Im not grasping what your saying. Just having trouble getting my head around it all, but do appreciate the help.

IBUs get diluted as you add water. An IBU is just a certain amount of alpha acid per unit volume, so as you dilute the volume the IBUs dilute linearly.

The complexity comes from hop utilization. Hop utilization is affected by the gravity of the brew and the length of the hop addition. So all other things being equal, you will get less hop utilization in an over-gravity boil relative to a normal gravity boil. Which means less IBUs at the end compared to how many grams of hops you added.

I would suggest not worrying about it. Go with your recipe, make your beer, and if you need more or less bitterness, add more or less hops for your bittering addition next time.

If your method and equipment stay the same, then your evolving recipes will be adapted to your equipment (and palate)

...

If you have 18L at 40 IBU and you drain off 16L, you will have 16L at 40 IBU. If you now add 2L of water, you will have 18L at 35.6 IBUs

...

check this out

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

If you just hit calculate on the 1.050 brew, you get 35 IBUs, and 23% utilisation. If you adjust the brew to 1.060, you get 32 IBUs and only 21% utilisation. Which means you need to add 10% more hops to get the same IBUs. Of course, your brew is 20% over-gravity so, you need 20% more IBUs to get the same bitterness after diluting... which is 44 IBUs. To get 44 IBUs you need to add even more hops because of the lower utilisation.

Another 40% more hops. But you do end up with 20% more beer at 35 IBUs, after diluting

The Maxi-BIAB calculator calculates this for you. But it assumes no additional sugars are added during the boil.

I think the difference would be negligible. And it would be correct if you added boiling water instead of sparge water during the boil.

 

[Truman42]

Thanks for the link and explanation Stux. Will take your advice and will also try just adding boiled water at end of boil to dilute and see how things go.

Cheers.