How to Use Efficiency Numbers

So, I've read various threads on efficiency, but I am wondering what people do with that number.

Let's say that you typically get 80% efficiency, but the recipe you are following assumes 70% (e.g., Brewing Classic Styles states that 70% is assumed).

Do you adjust your grain bill down? Adjust the water up? Make no adjustments and brew a stronger beer?

I've been adjusting the grain bill, but then the guys at the LHBS give me funny looks when I tell them I am buying 3.94 lbs of some grain instead of an even number like 4.50.

So, if you are following a published (book or forum) recipe, do you buy the grain amounts specified or do you adjust them?

 

I rarely brew from recipes, but I would adjust the grain bill. But there is no need to be as precise as you are. You can simply use 4 lbs of grain rather than 3.94. Just round to the nearest ounce.

 

Alternately you can use your higher efficiency to increase the volume into the fermenter. 5.25 or 5.5 gallons instead of 5 gallons. If you take a reading with a refractometer (or cool a sample for a hydrometer reding) after the mash, you can calucalate efficiently and adjust your pre-boil and post-boil volumes.

 

Unless you hit 70.0000% exactly, measuring your grain that precisely probably isn't necessary; you can just adjust your boil time and/or finished volume to hit your numbers.

I usually scale my grain to the nearest quarter pound or so, then adjust the rest, including variability in efficiency, via volumes & boiloff.

 

Does this make sense?

If I expect a difference in extraction efficiency ahead of time, adjust the grain bill to try to hit the right OG.

If the gravity after mashing is +/- 1 or 2 (?) points of expected pre-boil OG, let it go. (What is a good +/- to just let it go?)

If the gravity after mashing is too low, do the math for what end of boil volume is needed to hit the OG I want and boil longer for more evaporation to get to that volume. I will have less wort than expected, but at the right OG.

If the gravity after mashing is too high, do the math for what end of boil volume is needed to hit the OG I want and add water to dilute to that volume. Adding cold water should be OK because this is before the boil. I will have more wort, but at the right OG.

 

Yup! Or, instead of adding water, you could just shorten your boil time.

I'm usually happy with +/- 2 points, but that is totally your discretion.