Efficiency/Gravity Question

[TBC27]

I’ve asked about this before and received valuable feedback, but I’m going to ask about this topic again.

I just wrapped up another brew day. I was making a blonde ale that I plan to add coffee beans to the keg for a couple days right after racking. Below are pics of the recipe as well as stats from brewersfriend based on my notes and measurements from said brew day.

My SG/pre boil gravity was 1.047 when brewersfriend estimated it should be 1.037. How in the heck can I be so far over my SG/pre boil but only hit the OG on the nose? I was figuring I’d end up with an “imperial” blonde ale on my hands.

I used 4.55 gallons of strike water. I used 4.55 gallons of sparge water. I ended up with 7.25 gallons of wort pre boil (a tad low). I waited until the wort was boiling a few minutes before measuring SG/pre boil gravity. I even let the sample cool a bit before using my refractometer.

At the end of the day, I hit my OG number so I am happy and Brewer’s Friend indicates I had 71% brewhouse efficiency which is only 1% lower than my default settings, but it just seems so weird that my gravity readings are so high pre boil and then in the expected range post boil.

 

[chickypad]

Slightly missing the volume might account for a few pts but looks like you are way off. Must be a measurement error then. I would trust the post boil more than the pre-boil reading as long as it was corrected for temp. I know you said you waited a few minutes to get the pre-boil but maybe it wasn't enough to fully mix the high gravity first runnings and your sparge. Did you stir at all or just count on the few minutes of boil to mix?

 

[leonardoreges]

If pre boil volume is lower than expected, SG is gonna be higher for the same amount of grains, it’s just less water to dilute the sugars.
Plus, if you read SG some minutes after boiling started, it’s not your SG, it’s higher that that.
And third, maybe when designing your recipe you set your boiling losses by evaporation too high.

 

[LarMoeCur]

When you say "let the sample cool a bit before using my refractometer". How long is a bit? How big was the sample? Even if your refractometer has ATC they are notrious for been off if the sample is to hot.

When I pull a sample. I pull enough to check pH and gravity. That 1/2 oz of fluid can take quite a few minutes to get down below 100F. Now if you just pulled a pipit full is will cool very quickly.

 

[BLL]

It's not uncommon for preboil readings to be off if the wort isn't mixed well. It's more common on a production scale where the volumes are much larger and stratification can be a real issue, but the same principals apply to any volume. Refractometers are pretty inaccurate as it is, but they are more susceptible to giving misreadings under such circumstances. It could also be because you're refractometer was a little dirty.

 

[TBC27]

I stir fairly frequently around the hot break so I’m pretty confident my first and second runnings were mixed. I pulled two pipits full of wort after ~3 minutes after the boil started and waited another 3 minutes before measuring the wort with my refractometer. Maybe I’ll use a hydrometer as a comparison during my next brew.