Need Topup calculation help please

[morethanworts]

I have a kit which I've done twice now and it has finished at 1.018 both times, after plenty of time. OG was 1.072 so this is decent attenuation. See the brew details below if you like*, but others concur that they get this FG as well.

I want to increase the batch size so that the FG ends up around 1.010, but keep the ABV around 7.3% in the increased batch size (before the priming sugar addition). Yes, I want less body in the final beer, and slightly less taste! It's also more bitter than I'd like, so increased batch size should help that too. So I need to calculate how much extra water to add at the start to achieve 8 points less gravity in the end, and how much extra sugar to add to keep the ABV at 7.3%.

Is there a way I can use the forum's "Topup Calculator (Volume Required)" to do this, or one of the other tools, or can anyone please help?

*In case you think I've gone mad wanting to do this, it is the Brewferm Abdij (abbey) kit - a style which is not supposed to be too full bodied and in which it is acceptable (and necessary) to add extra sugar of some sort, even commercially. I had a Rochefort 6 and a Bernardus last night and they were less full of taste and definitely thinner bodied than mine. I do like the basic taste of my (6 week old) Abdij very much, it's just a bit too full bodied and full-on.

 

[morethanworts]

OK - total silence on that one, but I think I may have finally worked out the maths myself: I would still be grateful for anyone confirming if my calculations and logic look correct (or if this may even have the desired effect I described above!).

Old brew was 7.3% ABV (excluding priming) in 9L, so it contains 0.657L alcohol.

I know that around 7.4 points on the hydrometer represents roughly 1% alcohol and this is coincidentally around the difference in FG that I want to achieve. So 0.657L alcohol will represent 6.3% of the new batch size (if my logic is right).

(0.657/6.3)*100=10.43L (new batch size)

To raise the ABV back up to 7.3, I know that 18g sugar yields about 1%ABV in 1 litre, so:

18*10.43=188 (the additional cane sugar or equivalent to add)

Does this look OK? :hmm:

 

[calumscott]

You can indeed use the calculators to do this:

First, lets liquor back with "Topup Calculator (Volume Required)"

Original Gravity points       : 1072
Original volume               : 9
Topup Specific Gravity points : 1000
Target Specific Gravity points: 1064

Which tells us we need 1.1l

Next lets work out the sugar required using "Topup Calculator (SG Required)"

Original Gravity points       : 1064
Original volume               : 10.1
Topup volume                  : 0.1 *
Target Specific Gravity points: 1072

* - you have to put in a volume or it doesn't like the calculation...

Gives a sugar equivalent of 232g

So morethanworts off the top of the head calculation isn't too bad at all!! :clap: :clap: :clap:

 

[morethanworts]

Thanks Calum! I didn't think of using the calculators that way, but I understand now. :thumb:

Now you've pointed it out, the 'SG Required Calculator' will actually let you enter a nominal 0.01 in the topup, which then brings the sugar reading down to 215g, which is even closer to the result I had worked out.

It would be interesting to know what assumptions the calculators are making there, to explain our slightly different results, but my modest skills are certainly are going to negate any further maths! The calculators must either assume that it takes up to 21.3g sugar to yield 1% ABV in 1L, or that the 8 points difference (topup) doesn't equate to 1% ABV (we can't enter 7.4 point differences to test), or a combination of differences in both assumptions, I guess.

 

[calumscott]

Well I could tell you because I wrote the basis of them...

...but then EskiBrew (Martin) implemented them...

...and I've since forgotten what I wrote in the first place!!! :lol:

 

[morethanworts]

Just realised, that all seems neat, until you ignore what you've done to get there and instead just calculate the expected ABV in the new 10.1L batch. If we've added enough sugar to bring it back to 1.072 after the topup, and it fermented down to 1.010 (which was one of the main intentions), then the ABV would be around 8.2%, rather than the 7.3 wanted.

Have I woke up today and confused myself, or have we gone wrong somewhere?

 

[bunkerbrewer]

Just realised, that all seems neat, until you ignore what you've done to get there and instead just calculate the expected ABV in the new 10.1L batch. If we've added enough sugar to bring it back to 1.072 after the topup, and it fermented down to 1.010 (which was one of the main intentions), then the ABV would be around 8.2%, rather than the 7.3 wanted.

Have I woke up today and confused myself, or have we gone wrong somewhere?

Unless I've not understood, you need to factor in attenuation of the yeast? 1.072 down to 1.018 is 75% attenuation - perfectly reasonable, whereas 1.072 down to 1.010 is 86% attenuation.

If you want 7.3% ABV from a FG of 1.010, I think you're shooting for an OG of 1.065, but you'd still need to get 84% attenuation - if my maths is right :)

[Edit] You could try the "Saison" trick of adding champagne yeast (or something neutral like WLP001) after the initial pitch of yeast has fermented out - this should help dry out the beer

 

[morethanworts]

Just realised, that all seems neat, until you ignore what you've done to get there and instead just calculate the expected ABV in the new 10.1L batch. If we've added enough sugar to bring it back to 1.072 after the topup, and it fermented down to 1.010 (which was one of the main intentions), then the ABV would be around 8.2%, rather than the 7.3 wanted.

Have I woke up today and confused myself, or have we gone wrong somewhere?

Unless I've not understood, you need to factor in attenuation of the yeast? 1.072 down to 1.018 is 75% attenuation - perfectly reasonable, whereas 1.072 down to 1.010 is 86% attenuation.

If you want 7.3% ABV from a FG of 1.010, I think you're shooting for an OG of 1.065, but you'd still need to get 84% attenuation - if my maths is right :)

[Edit] You could try the "Saison" trick of adding champagne yeast (or something neutral like WLP001) after the initial pitch of yeast has fermented out - this should help dry out the beer

Brewferm themselves state 1.010 as the target FG, even for the beers in their range that have an even higher OG, such as the Triple at 1.075! I would only be adding sugars that are 100% fermentable.

Who knows whether the remaining sugars below the current 1.018 are all unfermentable or whether it's just the yeast giving up...

Anyway, in reference to my original post, I have a kit that, when made up to 9 litres with 550g Golden Syrup added, gives an OG of 1.072 and consistently ferments down to 1.018. There surely must be a way to thin-out the original batch so that the end result will be around 1.010/11, but keeping the ABV around 7.3%. Even if we assume I had a 100% attenuating yeast, I still haven't worked out the maths yet.

 

[bunkerbrewer]

Anyway, in reference to my original post, I have a kit that, when made up to 9 litres with 550g Golden Syrup added, gives an OG of 1.072 and consistently ferments down to 1.018. There surely must be a way to thin-out the original batch so that the end result will be around 1.010/11, but keeping the ABV around 7.3%. Even if we assume I had a 100% attenuating yeast, I still haven't worked out the maths yet.

Yep, you'd need to liquor back so that the OG is around 1.065 rather than 1.072.

Using "gravity points", the gravity / volume equation must balance, so (9* 72) = (x * 65) where x is your new volume; x = 9.97 - so adding a litre of water should do it?

 

[calumscott]

Just realised, that all seems neat, until you ignore what you've done to get there and instead just calculate the expected ABV in the new 10.1L batch. If we've added enough sugar to bring it back to 1.072 after the topup, and it fermented down to 1.010 (which was one of the main intentions), then the ABV would be around 8.2%, rather than the 7.3 wanted.

Have I woke up today and confused myself, or have we gone wrong somewhere?

There's a flaw in all the logic!

I've just worked it through in Beersmith and you need to add 8 litres of water and a kilo of sugar to do what you want to do.

Here's how it should be done in the calcs (which actually gives a totally different number because I was working with BS's estimates of gravities):

Topup Calculator (Volume Required):

Original Gravity points       : 1015
Original volume               : 9
Topup Specific Gravity points : 1000
Target Specific Gravity points: 1010

Gives 4.5l


Now calculate your best guess OG with just the original ingredients:

Topup Calculator (OG Expected)

Original Gravity points      : 1072
Original volume              : 9
Topup Specific Gravity points: 1000
Topup volume                 : 4.5

Gives 1049

Now work out the sugar equivalent to get back to 1067 (so the original 1072 less the 5 points FG we're hoping for):

Topup Calculator (SG Required)

Original Gravity points       : 1049
Original volume               : 13.5
Topup volume                  : .01
Target Specific Gravity points: 1067  

Gives 641g of sugar.

:thumb:

 

[morethanworts]

Thanks Calum, I will grind that through my mind again so I understand it better!

Thanks too, bunkerbrewer, although I had just composed a post (now cancelled) asking how you can add a litre of water to a 9 litre brew, without any extra sugar, and get the same ABV. There needs to be more ml of alcohol from somewhere, to keep the %age the same in the larger batch. What if I added 5 litres (and no extra sugar)?

ADDED: I want it to be significantly less bitter - I think the Abdij is considerably over-hopped for the style, but would the malt taste also become non-existent in a such a massively liquored-back batch?

 

[bunkerbrewer]

Thanks too, bunkerbrewer, although I had just composed a post (now cancelled) asking how you can add a litre of water to a 9 litre brew, without any extra sugar, and get the same ABV. There needs to be more ml of alcohol from somewhere, to keep the %age the same in the larger batch. What if I added 5 litres (and no extra sugar)?

That's where the attenuation of the yeast comes into play :)

You'd need 84% attenuation to get the same ABV, instead of your 75% (1.072 -> 1.018). So more of the sugar is converted into alcohol. In reality I suspect you'd get it down to about 1.016 without extra help, giving you about 6.5% ABV.

 

[morethanworts]

Thanks too, bunkerbrewer, although I had just composed a post (now cancelled) asking how you can add a litre of water to a 9 litre brew, without any extra sugar, and get the same ABV. There needs to be more ml of alcohol from somewhere, to keep the %age the same in the larger batch. What if I added 5 litres (and no extra sugar)?

That's where the attenuation of the yeast comes into play :)

You'd need 84% attenuation to get the same ABV, instead of your 75% (1.072 -> 1.018). So more of the sugar is converted into alcohol. In reality I suspect you'd get it down to about 1.016 without extra help, giving you about 6.5% ABV.

But how can you be sure that there were any (or at least 'many') fermentable sugars left in the 18 points of the original brew?

 

[bunkerbrewer]

But how can you be sure that there were any (or at least 'many') fermentable sugars left in the 18 points of the original brew?

You can't :) (Not without complex analysis, as far as I know)

But if you're adding simple sugars, there's a reasonable chance. Sometimes the only way to know if a brew is going to work the way you want is to try it and see, and learn the lessons for next time :)

 

[morethanworts]

Thanks both :thumb: I haven't quite got my head around your working yet, Calum You said the figures would be slightly different - something to do with Beersmith's estimates - but I'm still slightly lost.

My OG has been 1072, FG 1018. I'd like FG 1010, but keep the 7.3%ABV. If I get to understand your process, I will run it through the calcs myself.

The attenuation seems like an issue, as BB points out. I would consider buying a known high attenuating yeast, making a big starter, and pitching that into the existing batch, but I want to lessen the bitterness too (without adding malt/body), so I guess I must increase the batch size first.

I really want to refine my methods and improve my understanding before moving (back) to extract this time around, so I'm not against pitching a liquid yeast starter - even in a kit. It seems one stage that is often missed out: then you get to extract/partial mash, and have all the other variables at play.

Added - Maybe I should give BB's Saison idea a try too.

 

[calumscott]

Attenuation should be OK I think. Your FG is partly the attenuation of the yeast and partly stuff that it would never manage to eat anyway...

So all the stuff that it wouldn't eat gets watered down and replaced with stuff that it can (simple sugar) so I think you should be able to achieve your aim without the yeast packing in... especially with brewferm's own yeast.

Failing that, if you get it down and it stops short of where you want it, bung in a nicely rehydrated US-05 to finish it off. It's a beast of a yeast and eats pretty much everything!