Efficiency Too High (91%)?

[RCubed76]

My first batch I used grain milled at the online retailer, fly sparged, and the efficiency was terrible, 69-70%.
My second batch I milled my own grain, batch sparged, and got 78%.
The third (last one) I milled my own without changing the settings on the mill, batch sparged again, and got 91%.
Readings are with the cheapest refractometer I could find off Amazon. No stuck sparges thus far. Is this normal?
I would be happy to have good efficiency, but I can't understand why there would be 13% difference with no change in grind.
Any thoughts?

 

[Qhrumphf]

What were the gravities/grain bill sizes on the second two batches? If I brew a pale ale at 1.050 I'll hit 93%. If I brew a Barleywine at 1.120 I'll be lucky if I hit 80%.

 

[Qhrumphf]

Bigger beer means lower efficiency is the key take away.

 

[RCubed76]

Both were 5.5 gallon
2nd batch was a Marzen (78%)
4 lb MO
3.5 lb Pilsner
1 lb Carahell
1 lb Munich light
.5 lb Carapils
5 oz Victory
.5 Chocolate
Third was supposed to be a Best Bitter (91%) Now a Strong Bitter
7 lb Maris Otter
1 lb British Caramalt
1 lb Munich Light
4 oz Victory
11 oz Lyle's Golden Syrup (Invert)

 

[Qhrumphf]

If your process isn't dialed in, coupled with a slight grain bill increase, then yeah, that's a plausible difference. Those aren't different enough in gravity for me to blame efficiency alone though, so there's likely something else going on as well (could be a myriad of things)

 

[Jim R]

I remember patting myself on the back for increasing efficiencies into the 90-95% range with my own milling and then finally got a big time stuck sparge that I couldn't clear without dumping out the mash tun. I am not sure if it was right or wrong but I quickly backed off on my crush to get back to the 80's. Luckily I haven't gone through that brew day disaster again but I don't shoot for efficiencies in the 90's anymore.

 

[RCubed76]

I edited my grain bills above, remembering that I used 11 oz of Lyle's in the last batch. However, that was part of my Beersmith recipe. I'm sure I got one hundred percent efficiency from the syrup portion, but wouldn't the program account for that and adjust estimated efficiency accordingly?

 

[VikeMan]

I'm sure I got one hundred percent efficiency from the syrup portion, but wouldn't the program account for that and adjust estimated efficiency accordingly?

I don't use BS, but it ought to do that.

Did you also accurately measure the volume of your post boil worts at room temperature? A common rookie mistake is to just measure gravity and call it a day.

 

[RCubed76]

I did adjust for volume, but probably a bit warmer than room temp. With just a single drop on the refractometer, temp shouldn't make much of a difference, correct?

 

[VikeMan]

I did adjust for volume, but probably a bit warmer than room temp. With just a single drop on the refractometer, temp shouldn't make much of a difference, correct?

Hot wort on a refractometer can make a difference, contrary to popular opinion. I always cool it down before reading.

But I was asking if you actually measured the volume of the wort. If, for example, your volume in the "higher efficiency" batch was lower than the volume in the earlier batch, the gravity would be boosted, due to concentration (i.e. not actually due to efficiency).

 

[jimyoung]

Hot wort on a refractometer can make a difference, contrary to popular opinion. I always cool it down before reading.

Yes, and even warm. Try it yourself. Calibrate your refractometer with tapwater. Warm it slightly in the microwave, and measure again.

Especially if you're measuring repeatedly.. I measure every 15 mins in the mash, and I found previously that the refractometer itself would slightly heat up, reducing it's heatsinking ability. I'm much more careful now to cool in a broad, heavy ceramic plate before putting it on the refractometer