4 point spread between BG and OG

Brewed my 25th batch today. I've having issues between my measured BG and OG. Today I planned a 1.053 OG batch. I got a higher eff. than usual and my BG came in at 1.052. I adjusted my eff in Brewpal and Brew Target and both software told me that after a one hour boil I should be up to 1.063 or so. I changed my hop schedule to keep everything in balance.

So I boiled an hour cooled everything down and my OG going into the fermenter was 1.055 - 1.056. I'm off by about 8 points or so. Now I have a really hoppy beer with a projected ABV below what I was anticipating.

This was a 7.5 gallon batch but I've been getting the same numbers with 5.5 gallon batchs.

Can anybody tell me why I'm not getting my projected OG? I can't figure out what else I can adjust in my system.

Anybody out there?

Hmm. What was your pre-and post-boil volume? It sounds like you're boil-off rate is not as high as your software is predicting.

Pre-boil was 9.4 gallons. Post-boil was 8.2 gallons. So I'm pretty sure I'm getting where I'm supposed to go. About 12-13% evaporation rate.

(preboil volume x preboil gravity units) / postboil volume = postboil GU

(preboil volume x preboil gravity units) / postboil GU = postboil volume

1.052 = 52 GU x 9.4 = 488.8

488.8/8.2 = 59.61 or 1.059

taken into account the correct reading with temp comp and volume. To reach 1.063 you need to boil down to 7.7 gallons

That's what I was thinking as well. Are you familiar with BrewPal? I love the software but my numbers for OG are always off as compared to what it's giving me. Unless I'm not entering something correctly in my parameters.

Bizoune said:

That's what I was thinking as well. Are you familiar with BrewPal? I love the software but my numbers for OG are always off as compared to what it's giving me. Unless I'm not entering something correctly in my parameters.

Click to expand...

no I have that formula in an excel spreadsheet but I hardly use it i'm not too anal about gravity reading as long as there are in the ball park and I dont have a refractometer or a sightglass.

kryolla said:

(preboil volume x preboil gravity units) / postboil volume = postboil GU

(preboil volume x preboil gravity units) / postboil GU = postboil volume

1.052 = 52 GU x 9.4 = 488.8

488.8/8.2 = 59.61 or 1.059

taken into account the correct reading with temp comp and volume. To reach 1.063 you need to boil down to 7.7 gallons

Click to expand...

And to account for the rest of your difference, your final volume is really probably more than 8.2 gallons because, I presume, you're leaving wort behind with the cold break. If that's the case, and you're leaving half a gallon behind, then you get:

488.8/8.7 = 1.056 with half a gallon left behind with the cold break

This fits exactly with what you got for your OG.

I got the same problem, as a post boil og of 1.061 with 27 liter and ended with 18.5 liter and only 1.064 :O I targeted my of but had 4.5 liter off my 23 L planned and IDK why!

Anybody else having problems with BG and OG calculations using BrewPal?

BrewPal has been giving me fits since I bought it and the author no longer seems to be around =/

-Scott

Either your volume measurements are wrong or your gravity measurements are wrong. Furthermore, your evaporation rate is different than the assumption you gave the software.

I think mkling has the solution to your problem. How are you measuring your volume?