2 Batches, Same Equipment, Different Efficiency

[triangulum33]

I brewed a 1.067 Porter AG and got 81% efficiency. Right after, brewed a 1.076 IPA and got 70%.

I bought the grain and had it milled at the same time at my LHBS. Both batches hit ~152* in the mash. Both were stirred well several times during mash and sparge. I had 2 friends there that were brewing too, and they agreed that both batches were brewed basically the same.

I'm wondering why such a large difference in efficiency? Can the quality of the grain affect this?

 

[m1k3]

70-81% sound like great numbers to me.

I lose efficiency as I mash more grain (when shooting for higher gravity).

I would not suspect the grain as the issue and you ruled out the crush.
How exact are your volume measurements when calculating efficiency?

 

[Qhrumphf]

A couple thoughts:

-were there differences in the base malt (ie MO vs. domestic 2 row vs. pils malt)? Different grains crush different ways, and if you were using a different malt the crush could be slightly different

-as alluded to above, when you mash a higher gravity beer, unless you're intentionally gathering more runnings during the sparge to get a larger preboil volume and then boiling it all back down, you're effectively removing less sugar during the sparge which will lower your efficiency compared to a lower gravity batch.

 

[BobC]

What was your water to grain ratio? It can effect your efficiency a little.

 

[triangulum33]

The water/grain ratio was 1.25qt/lb on both batches.
I was aware of diminishing efficiency with increasing OG, but i didnt expect this much of a difference.

 

[stjackson]

Did you sparge at the same rate on both batches? Faster sparges will result in lower efficiency. I know you said that both batches were processed the same, but I have played around with sparge rates and it can dramatically affect efficiency.

 

[TyTanium]

How exact are your volume measurements when calculating efficiency?

+1, try calculating everything with a 1qt swing, see how much your efficiency moves.

Too small a sample size to be concerned, IMO.

 

[SouthBay]

Sounds like water chemistry potentially. Darker beer = lower ph = better conversion

 

[triangulum33]

Sounds like water chemistry potentially. Darker beer = lower ph = better conversion

I thought water chemistry just affected flavor. I didnt realize it could affect efficiency.

 

[BrewKnurd]

I thought water chemistry just affected flavor. I didnt realize it could affect efficiency.

Yup. pH affects how well the enzymes work.

 

[triangulum33]

I add Gypsum and CaCl2 to lower pH. I guess I should make adjustments for different beers...