Efficiency Questions

[cubbie]

I posted this in the Robust Porter Recipe Advice thread, but thought it would get lost in there so starting a new thread. Anyway......


Folks I brewed this yesterday and had some puzzling results with my efficiencies so just after some thoughts from others.

Recipe

Recipe Specifics
----------------

Batch Size (L): 24.00 Wort Size (L): 24.00
Total Grain (kg): 6.28
Anticipated OG: 1.060 Plato: 14.77
Anticipated EBC: 76.0
Anticipated IBU: 3.8
Brewhouse Efficiency: 75 %
Wort Boil Time: 60 Minutes

Pre-Boil Amounts
----------------

Evaporation Rate: 15.00 Percent Per Hour
Pre-Boil Wort Size: 28.24 L
Pre-Boil Gravity: 1.051 SG 12.65 Plato

Formulas Used
-------------
Grain/Extract/Sugar

% Amount Name Origin Potential EBC
-----------------------------------------------------------------------------
75.6 4.75 kg. TF Maris Otter Pale Ale Malt UK 1.037 6
9.6 0.60 kg. Weyermann Munich I Germany 1.038 15
4.8 0.30 kg. TF Chocolate Malt UK 1.033 940
6.4 0.40 kg. Weyermann Caramunich I Germany 1.036 100
3.6 0.22 kg. TF Black Malt UK 1.033 1270


TF grain was actually Bairds


Anyway as you can see I had my brewhouse efficiency at 75% (which Promash stats is your Mash Tun efficiency) , however mashing and when I recorded it in the kettle (just after I came to the boil) I got 1.062 which Promash tells me is 100% (Efficiency Calculator in Brewing session). Now even if I reduce my recorded volume (which was 31L) by 4% to account for the expansion of the wort at 100c that still has my Eff above 93%

Is it possible to get an efficiency that high?

Post boil after coiling I recorded the volume at 24L and into the fermenter at about 21.5 and a gravity of 1.071 (86% efficiency). In the kettle (before losses) that equates to about 89-90%

1.071 plugged into the recipe gives me an efficiency of 88%


Now to me these numbers just don't add up. I can see how a litre out in measurements here and there can make some difference, but the values all seem very high to me, are these numbers possible in a homebrew setup?

Secondly how can a measurement in the Kettle go from 100% start of boil (or 93% -4% volume for cooling) to 89-90% end of boil?


If anyone can offer some clarity that would be great.

All my measurements where done with a refractometer and I had another 2 blokes check them.

 

[Supra-Jim]

Hey Cubbie,

When you took your first reading from the kettle had you given the wort a good stir? I did this once without stirring the wort and basically at the bottom of the kettle was the nice rich 1st runnings, then gave it a good stir and re-checked and got a more reasonable gravity reading.

Cheers SJ

 

[cubbie]

Hey Cubbie,

When you took your first reading from the kettle had you given the wort a good stir? I did this once without stirring the wort and basically at the bottom of the kettle was the nice rich 1st runnings, then gave it a good stir and re-checked and got a more reasonable gravity reading.

Cheers SJ

Well I took the reading after it came to the boil (turned off heat while I took reading) so theoretically there should have been enough movement in the kettle to mix the wort. If anything I would have expected my reading to be lower had it not mixed (as it was taken from the top of the kettle).

 

[Sammus]

another possibility is that if you take the reading while boiling, a lot of the water will evaporate from the hot wort between when you take the sample and do the reading - this can affect the readings significantly.

 

[Gavo]

Did you take the wort from the tap? Even if you stir the wort you will still have the rich 1st runnings in your pickup tube.

Gavo.

 

[RobB]

I used to get 'too good to be true' measurements from my refractometer until I realised that it was evaporating, and hence concentrating, on the lens (the same problem that Sammus highlighted). You'll be taking a sample at about 70 degrees and even though it cools really quickly as you apply a thin film to the refractometer, I think a bit of evaporation still occurs, again because it's such a thin film.

I overcame this by chilling a stainless measuring cup in the freezer, taking a sample with a soup spoon and dropping it into the measuring cup which I then chuck back in the freezer for a minute or two. The sample cools quickly and now my refractometer readings agree with my hydrometer.

I'm sure there are other tricks for beating evaporation, but this one works for me.

 

[cubbie]

Did you take the wort from the tap? Even if you stir the wort you will still have the rich 1st runnings in your pickup tube.

Gavo.

Nope with a pipet from the top of the kettle.

Palmer has the following to say below..... So perhaps if I consider the 4% expansion of the wort and that I was say 1 litre out in my measurement that is an efficiency around 90% and therefore I have just done real well. 90% is more inline with my final efficiency readings.


The maximum yield is just that, a value you might get if all the mash variables (e.g. pH, temperature, time, viscosity, grind, phase of the moon, etc.) lined up and 100% of the starches where converted to sugars. But most brewers, even commercial brewers, don't get that value in their mashes. Most brewers will approach 80 - 90% of the maximum yield (i.e. 90% of the maximum 80%). This percentage is referred to as a brewer's extract efficiency and the resulting yield is the typical yield from our mash. The extract efficiency is dependent on the mash conditions and the lautering system. This will be discussed further in Section 3 - Brewing Your First All-Grain Beer.

For the purposes of our discussion of the typical yields for the various malts and adjuncts, we will assume an extract efficiency of 85%, which is considered to be very good for homebrewers.

 

[cubbie]

I used to get 'too good to be true' measurements from my refractometer until I realised that it was evaporating, and hence concentrating, on the lens (the same problem that Sammus highlighted). You'll be taking a sample at about 70 degrees and even though it cools really quickly as you apply a thin film to the refractometer, I think a bit of evaporation still occurs, again because it's such a thin film.

I overcame this by chilling a stainless measuring cup in the freezer, taking a sample with a soup spoon and dropping it into the measuring cup which I then chuck back in the freezer for a minute or two. The sample cools quickly and now my refractometer readings agree with my hydrometer.

I'm sure there are other tricks for beating evaporation, but this one works for me.

Will give that a bash.

 

[Gavo]

Nope with a pipet from the top of the kettle.

No problem, just I discovered that one a while ago when I got an apparent 110% kettle efficiency, :blink: anyway I still use the tap but recirculate a bit first.

Gavo.