# Beersmith Assistance - Low Abv



## itguy1953 (3/2/09)

I have noticed that Beersmith seems to underestimate the OG and ABV values for a brew, so I punched in some figures to see if someone can help me with the problem.

I put in a 1.7Kg can of Coopers Lager goo, 1Kg of Dextrose and 1 packet of S23 yeast.

I get an OG of 1.039, FG of 1.009 and an ABV% of 3.82. 

These figures all seem to low?

Any clues?

Barry


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## browndog (3/2/09)

And how much water are you adding there Barry?

cheers

Browndog


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## Gavo (3/2/09)

With 23 lt I get SG 1044 and FG of 1008, ABV 4.6.

Cheers
Gavo.


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## itguy1953 (3/2/09)

browndog said:


> And how much water are you adding there Barry?
> 
> cheers
> 
> Browndog



I have a batch size of 23 litres


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## itguy1953 (3/2/09)

gavo said:


> With 23 lt I get SG 1044 and FG of 1008, ABV 4.6.
> 
> Cheers
> Gavo.



These are the sort of figures I would expect, as a true k&K should give around 4.5% ABV. 

Now we need to find out what I am doing wrong.

Barry


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## browndog (3/2/09)

Are you sure your hydrometer is accurate?

-BD


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## Gavo (3/2/09)

Just looked again. With S-23 yeast FG 1011, ABV 4.24%.

Cheers
Gavo.


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## buttersd70 (3/2/09)

Barry R said:


> These are the sort of figures I would expect, as a true k&K should give around 4.5% ABV.
> 
> Now we need to find out what I am doing wrong.
> 
> Barry



You're not doing anything wrong.....1039 in 23L is correct for 1.7 kg of lme and 1kg of dex. Beersmith says 1039, Brewsta says 1039, promash says 1039, my manual spreadsheet says 1039.....
The fg is subjective though...the average apparent attenuation for the yeasts is based on a malt wort, so having dextrose in there would skew the figures. You have to account for the higher fermentability of the dextrose portion, which beersmith doesn't do. It works FG based on OG and the manufacturers average attenuation values, irrespective of wort composition. (as an interesting aside, it doesn't take the mash parameters into account either, if you do AG.) It would more likely be 1007-1008 fg.

Edit....don't forget that that ABV is post ferment only...by the time it's carbonated in the bottle, it would be adding approx 0.3% for 2.5vol CO2. So for a beer going 1039-1008, it would end up as 4.5%, for 1039-1010, it would be 4.2%


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## itguy1953 (3/2/09)

gavo said:


> Just looked again. With S-23 yeast FG 1011, ABV 4.24%.
> 
> Cheers
> Gavo.



Still this is different to the 3.82% ABV I am getting.

Wonder why?

What av attentuation are you assuming for S23? I have 75%.

Barry


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## itguy1953 (3/2/09)

buttersd70 said:


> You're not doing anything wrong.....1039 in 23L is correct for 1.7 kg of lme and 1kg of dex. Beersmith says 1039, Brewsta says 1039, promash says 1039, my manual spreadsheet says 1039.....
> The fg is subjective though...the average apparent attenuation for the yeasts is based on a malt wort, so having dextrose in there would skew the figures. You have to account for the higher fermentability of the dextrose portion, which beersmith doesn't do. It works FG based on OG and the manufacturers average attenuation values, irrespective of wort composition. (as an interesting aside, it doesn't take the mash parameters into account either, if you do AG.) It would more likely be 1007-1008 fg.
> 
> Edit....don't forget that that ABV is post ferment only...by the time it's carbonated in the bottle, it would be adding approx 0.3% for 2.5vol CO2. So for a beer going 1039-1008, it would end up as 4.5%, for 1039-1010, it would be 4.2%



Thanks Butters.

I understand that malt only partially ferments out, and I thought that this is what the avg attenuation figure was supposed to reflect. 

Now thinking about it, I also believe that Dextrose fully ferments. 

So, should the av attenuation be a weighted average of 75% for the malt, and 100% for the dextrose.

Something like - (75%*1.7kg*80% (malt in the goo) + 100% * 1kg)/(1.7*80%+1)=85.6%??

If I put this into Beersmith I get FG of 1.005 and ABV% estimate of 4.35%, which is closer to what I would have expected.

Comments? 

BTW, I put up this simple brew, to assist in discovering the problem in the way I am using Beersmith. I normally put in a lot more malt, and a little dex, but I am always getting OG's higher than Beersmith predicts.


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## buttersd70 (4/2/09)

Barry R said:


> Thanks Butters.
> 
> I understand that malt only partially ferments out, and I thought that this is what the avg attenuation figure was supposed to reflect.
> 
> ...


Close, but not quite. You can't just average for the entire amount. You can work it out based on the formula 
FG=OG-(Average attenuation x OG).
If you convert the ingredients to dry weights (ie for liquid, its 0.8x weight), then work out what percentage of the total extract amount each ingredient gives, (by adding all the dry weights...then dividing the dry weight of each ingredient by the total dry weight) you can sub the Average attenuation with 92% for the dex (which is an average fermentability for dextrose monohydrate).....so for example
1.7*0.8= 1.36. +1kg for dex. =2.36 total extract weight. 
1/2.36=42.37....so the dex makes 42.37% of the total extract weight. So,

0.4237x(39-(0.92x39)) + 0.5763x(39-(0.75x39)) = 6.94
So it would be 1.007.

btw, you can do the same thing for maltodextrin content...just factor in 0 for the attenuation.

Having said that, numbers are all fine and well, but there are *many *factors that influence the attenuation of the yeast, and a projection of FG should _only _ever be used as a (_very_) general guide. Only a stable hydrometer reading over consecutive days is an accurate indication of end of fermentation.

EDIT....don't get too hung up on yeast attenuation...the attenuations that are listed by the manufacturers or in software are a guide only, based on experience over a wide range of worts, then averaging the results out.


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## Gavo (4/2/09)

buttersd70 said:


> You're not doing anything wrong.....1039 in 23L is correct for 1.7 kg of lme and 1kg of dex. Beersmith says 1039, Brewsta says 1039, promash says 1039, my manual spreadsheet says 1039..






buttersd70 said:


> FG=OG-(Average attenuation x OG).
> 
> 1.7*0.8= 1.36. +1kg for dex. =2.36 total extract weight.
> 1/2.36=42.37....so the dex makes 42.37% of the total extract weight. So,
> ...



Butters, Thanks to your time and effort I am getting a handle on the numbers involved in these calculations. 
I have tried a few things with beersmith and can get the same numbers as you. By looking at your formula I am guessing that the calculation you have allows for potential for dextrose to be 1039 SG. So... when I change the potential for dextrose to 1039 and the average attenuation to 92% I get OG numbers in the 1039 ballpark. I normally have dextrose potential set for 1046 SG and a dry yield of 100% (is dry yield the same as average attenuation?), Link Here for beersmith potential for dextrose. I like the max in batch advise.

From memory when I did K&K I usually got a measured OG of 1042 - 1044. This number is from memory only as I never recorded these measurements back then. I am not about to to a K&K just to check it. <_< 

As you have said numbers are one thing, good to play with and used as a guide, but the hydrometer readings will give the accurate indication of specific gravity.

Cheers
Gavo.


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## buttersd70 (4/2/09)

Gavo, dry yield values and attenuation values are two entirely different things. Dry yield (as far as sugars are concerned) refer to the amount of dry sugar available in the product...so liquid malts are ~80% (because 20% is water), simple sugars are 99-100% dry, dry malt extracts are 95-97% (they have moisture content). The fermentability of the dextrose is lower than its dry weight, because it is a monohydrate....it is not anhydrous.  

I don't know how you are managing to get a higher OG in beersmith...I made no changes to the dry yield from default values. Same in promash. And manual calculations turn out the same. 

The formula for gravity are as follows;where sgp=specific gravity points, EE= extract efficiency as a decimal (grain only, otherwise ignore it), wt = weight, v = volume. 

using HWE (another way of experessing potential....which doesn't make it's way into beersmith. but 386HWE=100%dry yield),
sgp= hwe x EE x wt /V............all quantities in metric.

Using ppg;
sgp = Wt(lb) x ppg x EE / V(g)............all quantities in US measures.

So, without using a program, the example at hand is 1.7kg of lme (310HWE) and 1kg of dex (386HWE). EE is irrelevant, because we;re dealing with extract.
spg = (386 x 1)+(310 x 1.7) /23
= 386 + 527 /23
= 913/23
= 39.69 points, which rounds up to 1040. (the 1 point difference to beersmith is due to the potentials in the ingredient list not being exactly 100 and 80...depends on which brand you pick. It'll go up or down a point either way, depending on rounding, but 1 point is purely academic anyway.)

You could get the same result with the ppg...the only problem is you would need to convert all measures to fit the damn formula.  Easy enough if you do it in a spreadsheet, though.....alternatively, you could convert the dyfg to hwe by multiplying by 386.

There was a poll recently 'which software do you use', and there were a couple of responses (don't know who from) saying pad and pencil....these are the formulas that would be used. As an extension to that, if you have a recipe of a given volume adn known OG, and you want to know what the og would be at a differant volume....you multiply by the original volume, and divide by the new.


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## Gavo (4/2/09)

buttersd70 said:


> Gavo, dry yield values and attenuation values are two entirely different things. Dry yield (as far as sugars are concerned) refer to the amount of dry sugar available in the product...so liquid malts are ~80% (because 20% is water), simple sugars are 99-100% dry, dry malt extracts are 95-97% (they have moisture content). The fermentability of the dextrose is lower than its dry weight, because it is a monohydrate....it is not anhydrous.
> 
> I don't know how you are managing to get a higher OG in beersmith...I made no changes to the dry yield from default values. Same in promash. And manual calculations turn out the same.



Bang, got 1039 in Beersmith. My entry for the extract had a dry yield of 94% (don't know where I got that from). I changed it to 80% and now get 1039 for 1.7kg kit and 1kg of dextrose in 23 lt of water. Sorry about that Barry... if you want to up the ABV you are going to have to add some malt.  
I now stand for correction.  

Butters you still baffle me with numbers, however keep them coming so as to expand our brewing knowledge. Just a good thing they are used as a guide and not 100% paramount to making great beer. Well they might be 83.67% of the time. :lol: 

Cheers and thanks for the brain teasing session.
Gavo.


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