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How to properly utilize the IBU/SG ratio field

BlackDog-Brewery

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The IBU/SG field must be the most underutilized / ignored features in BeerSmith.  There are very few hits on Google regarding how to best utilize this field.

When I first started brewing porters and stouts I thought to myself "How can I possibly be enjoying this new bottle of beer if the IBUs are 50, 60, or even 70" . . . "This can't be right because I don't like west coast IPAs or any IPA's that begin to exceed the 50 IBU level"

That's when I discovered the "perceived bitterness" of a porter or stout is much less than the IBUs that are shown on the recipe.  In fact, out of the 30 micro-breweries by me, most of them have removed the "IBU" number from their chalkboards so it doesn't scare the customers away from trying some of the beers.

So on to my question . . . .

A fellow brewer shared his recipe for cloning a S'More Stout.  It took 3 recipe versions to balance the graham cracker / marshmallow taste.  There are 9 different specialty grains besides the base malt.

He said that it is critical for the IBU/SG ratio in BeerSmith to fall between 0.5 and 0.6

After nearly an hour of tweaking the recipe in BeerSmith including changing:

-  The base malt quantity

-  The bittering hop addition quantities

-  The bittering hop addition times

. . . . I realized there were probably 5 combinations that would get the IBU/SG ratio between 0.5 and 0.6 without changing his desired IBU recommendation of 43.  One of the things I noticed is that some combos created large changes in the estimated ABV.

Many people have tried to clone a S'More Stout and failed miserably.  So how do I utilize this great IBU/SG "perceived bitterness" field without changing the whole outcome of the brew and accidently screw up the taste just because the recipe wants the ratio to be within a certain range?

Out of all of the combinations that I tried, adding 2 more pounds of base malt got the ratio and the total IBUs to exactly where the recipe wanted.  But the estimated ABV went from 5% to 6%, and I'm not sure what effect the additional malt and higher ABV will have on the taste.

Are there any brewers out there that can share their "best practices" of what part of a recipe to adjust first when the recipe calls for a specific IBU/SG ratio?
 
BeerSmith has a lot of moving parts. The abv calculation is based on the maximum attenuation available from your yeast. Since you can control the yeast conditions, simply change the attenuation to the level you expect.

If I don't have equipment specs, I'll use the recipe volume and zero out all volume losses.

I start by putting the grain in to the same percentages as the original. The mash schedule is checked to make sure it matches the recipe. Then, I'll adjust the efficiency to match the recipe gravity.

The next step is to add the hops as listed in the recipe, paying attention to the AA% differences between recipe and the Hops database. I need to also make sure I'm using the same calculation (Rager/Tinseth) that is used in the recipe. Once I have parity with those items, if the numbers don't match, I might adjust the amount of an addition or two, or adjust the timing a little. If I'm +/- 3 IBU, I won't change aything.

At this point the BU/SG ratio should match, as should color.

Yeast is the very last thing I'll adjust.

The closing step is to add all of the basic stuff needed in a recipe, like Irish moss, finings, water, etc., and then use the Scale Recipe function to set the recipe to my equipment profile.

 
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