# Maths In Brewing / Hops



## Fatgodzilla (12/12/07)

In these recipes threads two things stand out on some of these recipes.

1. If the recipe says a 50litre brew, can we automatically scale back everything by 50% for a 25 litre brew? Is there anything that is exponential in our calculations ?

2. If a recipe says hop flowers, how do we convert to pellet ? I'm sure there is likely to be a chart or table somewhere, just haven't seen it (or do people just adjust through Brewsmith / Promash)

3. If you grow fresh hops, like many here, how do we calculate the bitterness ? Is there a kit somewhere to do this ?


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## Screwtop (12/12/07)

Fatgodzilla said:


> In these recipes threads two things stand out on some of these recipes.
> 
> 1. If the recipe says a 50litre brew, can we automatically scale back everything by 50% for a 25 litre brew? Is there anything that is exponential in our calculations ?
> 
> ...



Do you have Beersmith or some other Brewing Software FG?


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## JasonY (12/12/07)

For volume changes you can scale the recipe in proportion to the batch size (eg 50% of the hops & grain for half the volume). For AG the recipe would be using the posters efficiency so your system may be a bit different so you have to take that into account. There is a reduction in utilisation when using pellets compared to flowers, can't remember the numbers so if you also changed that you may want to research a little. I don't think its too much of a killer but.

Software makes it all easy.

As for homegrown, use them as late additions to be safe on bittering otherwise estimate it based on the typical amounts for those hops and then use taste to correct future batches. I know the ones I grew before I moved didn't have much of an aroma (chinook) so I would have not assumed they were anything like the US ones (perhaps future crops will be better for me once the bine is stronger).


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## Trent (12/12/07)

I am fairly sure the accepted thinking behind flowers versus pellets is that pellets give about 10% better utilisation that flowers, so I would reduce the bittering charge (if you are using pellets) by 10%. BUT, as JasonY pointed out, you are using hte recipe developers efficiency and utilisation, and you system is more than likely different.
If the recipe states the IBU's, then just use that, rather than addition of a certain amount of hops - especially when often they dont include AA% in recipes, and that can fluctuate a percent or 3 from year to year. For instance, I am fairly sure Saaz is usually around 4% AA, but the saaz I was using this year was 2.3% (IIRC), and hence the same amount of each added to bitter will give a large discrepency in IBU's. There are heaps of variables at the end of the day, but if ya just halve everything and then work it from there, you should be fine.
All the best
Trent


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## crozdog (12/12/07)

FGZ,

I use software (brewsta) to help scale recipes. I enter the starting recipe then note OG, total IBU's, time and ibu's for each hop addition plus % of each ingredient in the grist. Once i have that info I then scale the volume back and adjust the efficiency figure to match my system. Next i adjust the ingredients to get the same ibu's and roughly the same % for each ingredient as the original

Sorry can't help with the hop q's.

crozdog


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