Boil vs Fermenter OG

[yesyves@gmail.com]

Hi

I just brewed a recipe where I scored right on my Boil gravity expected by BF (33 L @ 1.037), finished with the expected Wort Volume (27 L) but way lower OG (1.041 vs 1.045 expected).

Can it be something else than a Hydrometer reading error ?

Thanks !

 

[jmcnamara]

that seems really weird. did you correct for the temperature of the wort? I know that changes it a little, but i forget if it increases or decreases as the wort is hotter.

the hydrometer could have been sticking to the side of the beaker or whatever. try spinning it a bit first next time before reading it. This will also help to get the gunk and bubbles off the hydrometer.

also, and i don't think this is the case here, sometimes the little piece of paper in a hydrometer shifts a little bit up or down. That may be what happened here, but it's odd that the first reading was spot on. unless it happened sometime while you were boiling.

maybe take some readings in regular water and controlled samples of wort (where you either calculated what it should be or you use a friends hydrometer to calibrate yours)

 

[J A]

I've gotten high pre-boil readings time and again, even with careful cooling of the sample, etc. Since the OG is consistently more accurate being that the wort going into the fermenter is cooled and the volume is easy to measure, I consider that a better indicator of efficiency and tweak the numbers to line up with that. It usually means that the pre-boil gravity in the calculator shows several points lower than the hydrometer reading I got. It seems to be a common occurance and there doesn't seem to be an explanation, so I just ignore the pre-boil gravity except to see if I'm in the ballpark in terms of predicted efficiency.

 

[daggers]

does the brewer's friend recipe calculator use the OG for hop calculations as the fermenter OG or the boil OG? Because from what I understand the hop ultilization depends on the gravity of the wort pre-boil as opposed to the OG pre-pitch

 

[JJeffers09]

I believe it calculates post boil for OG.

 

[bazzamckazza]

it looks like BF doesn't factor in kettle losses when calculating post boil gravity
I've posted details here
viewtopic.php?f=5&t=3403

 

[De Brew]

BF recipe pre boil gravity estimate is not usable and has lead me astray numerous times. way low and it seems it does not correct for boil off as entered in your profile but more along the line of 1.5 gal per hr while my profile calls for .5 gph. I plan to use the tool calculators in the future to come up with my own estimate.

 

[GFHomebrew]

I'm usually within a few points of my expected pre boil gravity and I know given the pre boil what I'll get post boil going from previous batches using my equipment. I know I get 10points off a 90min boil and about 5-6off a 60 min boil. As for volumes yep I ignore Brewers friend mash volume and pre boil volumes and just work off my own estimated volumes going from experience using my equipment and also use Brewers friend as an indicator.
But once you do a few batches of similar grist sizes on your system you don't need Brewers friend to dial it in.

If I want more or less in fermentor I change my mash volume or sparge volume and tweek these to get my volume.
Leave the boil time the same that I think is a constant except if it's real windy or me gas runs out.

Another thing that can throw out my fermentor volume is weather or not I Pitch all my starter or decant and pitch.