What the heck happened here?

[shanecb]

First off, I was just up all night brewing, so sorry if I'm leaving out information I'm not thinking of.

We just did our first AG batch, and there's some stuff I really can't figure out. We used EdWort's Bee Cave Brewery Bavarian Hefeweizen recipe: https://www.homebrewtalk.com/f70/bee-cave-brewery-bavarian-hefeweizen-35679/ Consult it for ingredients and mash. The mash was pretty right on at 154-153 degrees the whole time. We batch sparged with about 5 gal of 168 degree water to get up to a boil volume of 7gal.

We saved some of the wort from after sparging and before boiling and let it cool to 60 degrees to get the gravity reading, instead of taking a hot reading and adjusting for temperature. Preboil, our gravity was 1.035, which is a 58% mash efficiency. Not great, but since it was our first go we didn't really mind. We chalk this up to a couple of things: our LHBS was having trouble with their mill, so we didn't get a great crush. Also, we didn't stir in the sparge water or let it set for a few minutes, which I've seen some people do. We just poured and collected it.

We boiled off about 1gal of liquid, since we couldn't get a vigorous boil stovetop. About another .5 gal or so was left behind with the crap at the bottom when we racked to the fermenter, giving us the total 5.5 gallon batch.

Now, we took a gravity reading for our OG. Temperature adjusted it came out at.... 1.035?! That would put it as the same as preboil, which makes no sense at all. We took three different gravity readings across two different people, with both getting the same reading. We adjusted all reading sfor temperature, and tested the hydrometer a few times with just water and it was accurate. How could this make sense? We even retested the preboil wort we still had and it too was 1.035.

How could the gravity have not risen to a decent level post boil, and not at ALL? Everyone had the same reading, everything was adjusted appropriately, and the hydrometer was determined to be accurate. Does anyone have any ideas what's going on? I guess we'll just have a real sessionable wheat beer, and it's not the actual reading we care about, just the fact that it didn't seem to rise at all.

 

[Frodo]

When you took the post boil OG and corrected it, what was the temperature of the wort? I don't trust the temp conversion charts unless it's below 90F or so at most. It's best to always cool to 60F to measure SG. If it wasn't cooled, you can still measure the OG - just grab another sample from the fermenter before fermentation starts.

 

[shanecb]

When you took the post boil OG and corrected it, what was the temperature of the wort? I don't trust the temp conversion charts unless it's below 90F or so at most. It's best to always cool to 60F to measure SG. If it wasn't cooled, you can still measure the OG - just grab another sample from the fermenter before fermentation starts.

It was cooled to about 73F, so it wasn't that far from 60F.

EDIT: Also, just to add, it's already fermenting. There were some bubbles coming up, but I pulled a small sample out with a wine thief to do another reading and it's already about 1.029.

 

[defenestrate]

when you took the reading pre boil, did you pull the sample from the entire 7 gal in the kettle or did you maybe pull the sample from a random point in the sparge? if you pulled the from the entire 7 gal, do you think the wort was mixed thoroughly in the kettle... while sparging the gravity is always changing so unless the kettle is thoroughly mixed, you may have a hard time getting an accurate reading with possible "layers" of collected wort.

 

[Frodo]

do you think the wort was mixed thoroughly in the kettle... while sparging the gravity is always changing so unless the kettle is thoroughly mixed, you may have a hard time getting an accurate reading with possible "layers" of collected wort.

That would be my next question as well. There is absolutely NO WAY for the pre-boil SG to be the same as the post-boil SG if you lost 1 gallon during the boil. If you didn't mix the wort in the kettle after the sparge, then that might explain it. Also, your 58% efficiency is pretty dang low regardless of the fact it was your first all grain batch. That said, I did get some poorly crushed grain on like my 3rd AG batch that I think caused a really low efficiency. Despite that possibility, I am thinking your pre-boil gravity measurement was incorrect.

 

[shanecb]

It was the full boil size, not a sparge sample, and we were sure to thoroughly mix it before we took the sample. I completely agree that it is impossible, so I'm trying to find out what the mistake could have been here or where we mixed things up.

Yeah, 58% is low, but we've identified why so I'm not too concerned with that at this point. The crush was rather poor, and we didn't let the sparge water sit in the grain (didn't know any better at the time).

 

[defenestrate]

are you figuring in the expansion and shrinking of the wort with temp changes? that was one thing i overlooked before when i couldnt get my numbers to match up... i believe it accounts for roughly 4% of the volume, i generally see a 1/4 gallon when finishing a boil with 6.5 gallons.

 

[shanecb]

I believe I'm taking that into account, yes. I think I'm just going to have to chalk this up to there being some sort of small mistake at some point in reading the SG and leave it at that. Everything I know of to take into account we did, so who knows. I'll just have to accept that one of the gravities were wrong haha. No worries, the fermentation went great and it looks/smells fantastic. Going to let it sit in primary for a week then bottle.

Thanks for all of the suggestions, though, in helping to clear this matter up!

 

[defenestrate]

its always reassuring that at the end of the day we still have good beer

 

[shanecb]

Cheers to that!