Temperature and Efficiency

[y2jrock60]

Last night my brew buddy and I brewed a 5 gallon batch of a Scottish 80. We mashed at 155-156 for 60 minutes with a 1.45 q/lb ratio, mashed out with 1 gallon of boiling water, stirred, let sit for a few minutes, vorlaufed, then drained like we usually do. However, we forgot to put the lid on our sparge water that was sitting outside and the temperature fell from 172 to 160. We didn't feel like heating it back up so we just used it anyway. We boiled for 90 minutes and ended up with exactly 5 gallons in the fermenter. Our estimated OG was suppose to be 1.075, we ended up with a 1.065.

This was our second time batch sparging, we've previously fly sparged our first 20 batches. After talking to some home brew veterans I discovered most of them batch sparge, because it's easier and they say just as efficient as fly sparging, so I thought I'd give it a try. Our first go round with batch sparging was about 2 weeks ago with a 10 gallon batch of a pale ale. We used the same 1.45 q/lb mash ratio and followed the same procedure with the exception of a 60 minute boil rather than 90 and sparge water that was actually around 175 degrees. Our targeted OG was 1.054, but we actually ended up with a 1.056 and a little extra beer in our fermenters. The only difference between the two brews was the batch size, boil time, and sparge temperature.

I'm just confused as to why there is a huge difference in efficiency. I'm not too concerned about being a few points off, but 10 points is kind of upsetting. The only thing I can think of, and I'm hoping it to be the culprit, is the sparge water temperature. Would a low sparge water temperature of 160 degrees impact efficiency negatively 10 points?

 

[TyTanium]

No. No way. Small sample size (n=1), so don't put too much weight on it. How accurate are your volume measurements? +/- 1 pint can move you a few points.

Batch sparging is theoretically less efficient (fly sparging = infinite # of batch sparges), so you may have lost a few points there depending on your process.

 

[y2jrock60]

My water measurements are pretty accurate. I use a bucket that has pint marks between every gallon mark and have tested it. I also measure my own grain at the homebrew store and crush it. My buddy measured all of the specialty grains for the Scottish, but I'm pretty sure he knows what he's doing since he's done it 50+ times.

I'm just confused, I had a +2 points on efficiency the first time I batched sparge and -10 points the second time around. The only difference was the first batch was 10 gallon, boiled for 60 minutes rather than 90, and was sparged with 175 degree water rather than 160 degree water like the second inefficient batch.

 

[billdog]

I batch sparge. I have noticed the same thing. In the begining I was sparging with water @168. I upped it on the same recipe to 175 and my efficiency went from 68% to 72%. From what I know of chemistry....the higher sparge temp allowed the sugars to more easily be absorbed by the water. Plus my mash filtered better too.

 

[y2jrock60]

I batch sparge. I have noticed the same thing. In the begining I was sparging with water @168. I upped it on the same recipe to 175 and my efficiency went from 68% to 72%. From what I know of chemistry....the higher sparge temp allowed the sugars to more easily be absorbed by the water. Plus my mash filtered better too.

That's good to know. I'm going to be brewing again so I'm going to make sure my sparge water is around 175 again rather than 160. If you received a 4% boost in efficiency with a 5 degree difference in sparge temperature, I'm hoping to receive an 8-10% with a 15 degree temperature difference.

I really hope that the low sparge water temperature is what caused the 10 point gravity difference. I was actually 2 points higher than my estimated gravity for my first batch sparge. It seems no mater what method I choose I can never get consistent results that I can compensate for.

I'm hoping that some of my questions will be answered tonight when I brew again.

 

[Denny]

No way could a lower sparge temp cause that kind of discrepancy. Kai Troester has shown that even using room temp water won't affect efficiency. If you sparge with really hot water (like boiling), you could possibly solubulize some more starch and raise your efficiency _maybe_ a point or 2, but not anywhere near 10 points. Crush is the first place to look. Did you crush it yourself? If not, the crush between the 2 batches could be different.

 

[TyTanium]

I agree with the theory that higher temp = more sugar dissolved, but I've never seen any convincing data that it provides a significant boost to efficiency. There are so many other factors that contribute to efficiency. Anecdotal evidence of a 4% bump one time doesn't convince me.

So to extrapolate a 15° difference = 8-10% efficiency change? No way. I'd be happy to be wrong, but I really doubt that's your issue.

 

[huge1s]

When calculating your expected gravity, did you use the same efficiency percentage for both beers? I believe that with bigger beers, you should expect an efficiency drop. I know that was my experience on my system. I usually get 78% - 80% and my one and only "big beer" was at 65%.

 

[y2jrock60]

The 10 gallon batch was based off an 80% efficiency and the 5 gallon batch 82%. If a 15 degree difference in sparge temperature didn't result in a 10 point change in gravity what did? I crush my own grain so I know the crush isn't the factor.

 

[henryred]

So u had 12.4 lbs of grain. A 12% efficiency drop. Did u stir between batches? Did u use 9 gals total?

 

[richkev]

y2jrock60,

You mentioned that you were fly sparging and then decided to switch to batch. I may have missed this, but what type of mashtun are you using? Are you using a kettle with a false bottom, or did you also switch over to a cooler/braid type of setup? I'm just curious about your setup.

 

[y2jrock60]

I stir after adding adding mashout water and sparge water. I follow beersmith for my water volumes and always end with the exact amount of suggested preboil water with very little water left in the mashtun. I use a cooler style mashtun with a cpvc manifold in the bottom. I've fly sparged in the past with mixed results, but decided to batch sparge since lifting 7+ gallons of sparge water to my sparging platform has become a pain, especially with 10 gallon batches.