Questions re Gravity Numbers

[ABG]

G'day guys,

I brewed an AG NEIPA over the weekend. The calculated numbers showed an estimated OG of 1.066 using the following grain bill (21L recipe):
2.5kg 2 Row
2kg Golden Promise
570g Carapils
340g Aromatic

I'm using a Robobrew and my first gravity reading (after mash out) was 1.068. I used 21L of water for the mash in, then 12L for the sparge. My reading after the sparge was 1.048. After a 1 hour boil, it climbed up to 1.052.

This is the first time my numbers have dropped so dramatically after a sparge.

A few questions:

1. Have I missed my numbers terribly, or have I just used too much water for the sparge and diluted the wort too much?
2. Does the temperature of the sparge water make much difference (mine was at 68C)?
3. What would you have done differently to come in closer to an OG of 1.066?

Thanks in advance.

 

[mongey]

How many l of wort did you end up with ?

 

[MHB]

Just very roughly you have 5.41kg of malt, to get 21L of 1.066 wort you would need 3.69kg of extract. assume the potential of your malt averaged 75% CGAI, that's 4.057kg available.
3.69/4.057=91% (near as), I doubt you are ever going to get much over 80% on a Grainfather. So I suspect you will be disappointed.
To your questions
1/ really its not enough malt or too much water for your equipment.
2/ Yes but not a huge amount, 78-80oC is optimum, but speed of lautering is probably more important, go slower.
3/ Make less wort.

Mark

 

[ABG]

How many l of wort did you end up with ?

31L pre boil. 23L in the fermenter (roughly 2-3L left below the outlet tap that I don't bother putting into the fermenter).

Just very roughly you have 5.41kg of malt, to get 21L of 1.066 wort you would need 3.69kg of extract. assume the potential of your malt averaged 75% CGAI, that's 4.057kg available.
3.69/4.057=91% (near as), I doubt you are ever going to get much over 80% on a Grainfather. So I suspect you will be disappointed.
To your questions
1/ really its not enough malt or too much water for your equipment.
2/ Yes but not a huge amount, 78-80oC is optimum, but speed of lautering is probably more important, go slower.
3/ Make less wort.

Mark

Thanks Mark. I really appreciate your detailed response.

Supplementary questions if I may. Why would you struggle to get over 80% on a Grainfather/Robobrew? What sort of efficiencies does a commercial brewery strive for?

Cheers,
Andrew

 

[ABG]

1/ really its not enough malt or too much water for your equipment.
Mark

You're spot on. I just put the numbers into the Grainfather calculator and it came up with 18L for the mash and 12L for the sparge. I was out by a full 3L!