Am I as inefficient as my calculations make out?

[markcurling]

Hi guys,

I just attempted my second all grain brew, was brilliant fun! I did the first one blind without any readings or measurements, so this time I made an effort to track what I was doing.

I used a Spitfire recipe which is available here:

http://www.hopandgrain.com/recipeSearch.aspx?name=Spitfire Ale

SPITFIRE ALE Shepherd Neam Faversham Kent.

25 litre batch OG 1045 ABV 4.7 35 units of colour 43 EBU

HALCYON PALE MALT 3754 gms
AMBER MALT 250 gms
CRYSTAL MALT 400 gms
WHEAT MALT 200 gms
TORRIFIED WHEAT 400 gms

HOPS Boil time 90 minutes

TARGET 30 gms
GOLDINGS 28 gms
Add 10 gms Goldings last 15 minutes.


Now, all seemed to go to plan, and I hit an OG of 1045 before pitching, which agrees with the recipe. However, I wanted to go a step further and look at the efficiency. I calculated the total available gravity points using the following table of malt extract potential:

http://hbd.org/uchima/tech/extract.htm

If my calculations are correct, the recipe above comes out around 76 points.

I worked it out in metric in full, but for the sake of simplification, 11 pounds of grain at 36 points per pound per gallon, for 5 gallons, gives 11*36/5 = 79 points. So 76 for the full calculation seems reasonable.

However, this means that an OG of 1045 is only 59% efficient!
So, my question is, was my brewing (and the brewing implied by the recipe) extremely inefficient, or is there a mistake somewhere in my calculation/understanding?

 

[jkarp]

Just converted your measurements to proper English values and plugged 'em into TastyBrew. Says you got 72.5 % which is damn fine.

Oh, TastyBrew can break down the calculations per grain so you can find out where you went wrong.

 

[markcurling]

Hi,

Thanks for the reply, could you explain how you got to that number? I plugged my numbers into it and got "potential gravity = 1.077", in agreement with my previous calculation, which means that my OG of 1.045 is 58% efficient?

Here is the output pasted from the calculator (some of the values may be different to yours due to slight changes to the recipe which I omitted in my post, but the changes are only minor compared to the error from 58% to 72.5%!)

Calculated for 5.279259776 gallons

Grain ppg X wt / batch size Points
8.28 lbs. of British Two-row Pale 38 * 8.3 / 5.3 = 59.6
0.99 lb. of British Amber 30 * 1.0 / 5.3 = 5.6
0.66 lb. of British Crystal 65L 34 * 0.7 / 5.3 = 4.3
0.55 lb. of Wheat Malt 39 * 0.6 / 5.3 = 4.1
0.55 lb. of Torrified Wheat 36 * 0.6 / 5.3 = 3.8
11.0 lbs. total Total Points: 77.3
Potential Gravity = 77.3 / 1000 + 1 = 1.077

 

[jkarp]

Well one big difference is you originally said this was a 25L batch. 25L = 6.6 gal.

 

[markcurling]

Ah that gives me a clue - I've been using imperial not US gallons, I'll run through it again...!

 

[markcurling]

Yes that puts my original spreadsheet up to 71% efficiency roughly in line with what you said originally, much more reassuring!

Thank you very much for helping me out (and sorry it turned out to be a boring units conversion!). My faith in my DIY brewing set up has been restored!

Mark

 

[jkarp]

Heh, no worries. You guys screwed up when you caved and gave up your own units of measure for that communist metric anyway.