Spike Brewing 12.5 Conical Fermenter Giveaway!

Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > FG lower than pre-boil gravity - WTF!

Reply
 
LinkBack Thread Tools
Old 03-07-2013, 02:22 AM   #1
TahoeRy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2012
Location: South Lake Tahoe, California
Posts: 305
Liked 43 Times on 35 Posts
Likes Given: 2

Default FG lower than pre-boil gravity - WTF!

OK, I am really confused right now and I cant find anything on the forms (from what I searched under). I just brewed a wet-hop cascade pale ale. My pre-boil gravity was 1.044 taken at 138 degrees. The hydrometer temp correction calculator I use,
(http://hbd.org/cgi-bin/recipator/recipator/hydrometer.html),
corrected this to to 1.059. My expected final gravity was at 1.052, so I expected to completely overshoot that. Well that didn't happen. I boiled for an hour (normally do a 90 min boil) and took my FG reading expecting a 1.064 +/- and got a 1.052 (after correcting for temp). This makes no sense at all to me. I checked the hydrometer in plain tap water after I got this reading and it checked out at a perfect 1.000. (I know I am supposed to check it in distilled water but the water in Tahoe is pretty soft and always checks out at a 1.000)

I have brewed a lot over the years and consistently brew a batch a week to keep the pipeline full and I have never, ever had a final gravity reading be lower than the pre-boil gravity. Does anybody think that this could be caused from using the wet-hops? Did they absorb some of the sugars that dry-hops would not? Thats the only thing I can think of right now as this just does not make any sense. Please shed some light on this for me.

__________________
TahoeRy is offline
 
Reply With Quote Quick reply to this message
Old 03-07-2013, 02:24 AM   #2
TahoeRy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2012
Location: South Lake Tahoe, California
Posts: 305
Liked 43 Times on 35 Posts
Likes Given: 2

Default

Wait, I didn't drink a beer while brewing today. Maybe the beer gods got me back for the huge mistake. Usually the first rule is to drink a beer while brewing, preferably a homebrew!

__________________
TahoeRy is offline
 
Reply With Quote Quick reply to this message
Old 03-07-2013, 02:28 AM   #3
cosmatics
HBT_SUPPORTER.png
Feedback Score: 3 reviews
Recipes 
 
Join Date: Apr 2010
Location: New Jersey
Posts: 245
Liked 18 Times on 18 Posts
Likes Given: 46

Default

I'm confused, you mean original gravity? You took a pre boil reading of 1.044, boiled for an hour. Took a reading and it was 1.052? What reading did your cooled wort have? I'm thinking there was just a messed up sample somewhere. Also what was your grain bill, target OG etc?

__________________
cosmatics is offline
 
Reply With Quote Quick reply to this message
Old 03-07-2013, 02:57 AM   #4
TahoeRy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2012
Location: South Lake Tahoe, California
Posts: 305
Liked 43 Times on 35 Posts
Likes Given: 2

Default

I took a gravity reading after I finished with my sparge and collected all of my runnings and that read 1.044 at 138 degrees. I corrected the reading using the online calculator and found a pre-boil reading of 1.059. I do this every session and never had this happen. Grain bill was really simple:

2-Row - 45.5%
Maris Otter - 45.5%
Victory - 9%

My expected pre-boil gravity according to beersmith should of been a 1.044 but I am pretty sure thats after I correct for temp. Maybe its not and thats where I am getting this confusion. I have always assumed it was after correcting for temp. My target FG should of been 1.052. So I hit my numbers according to the beersmith software. I just started using beersmith but every batch I have done so far with it (10 batch's) I ended up with a slightly higher FG compared to OG.

Maybe this is where I am having an issue. If I don't correct for temp, my numbers are dead on. I always correct my gravity readings based on temp then compare that to my data as its just a habit to correct the hydro readings.

__________________
TahoeRy is offline
 
Reply With Quote Quick reply to this message
Old 03-07-2013, 03:01 AM   #5
Yooper
Ale's What Cures You!
HBT_ADMIN.png
Feedback Score: 0 reviews
 
Yooper's Avatar
Recipes 
 
Join Date: Jun 2006
Location: Upper Michigan
Posts: 60,584
Liked 4342 Times on 3157 Posts
Likes Given: 845

Default

Remember that even with temperature correction tables, any SG sample over about 90 degrees is inaccurate- so inaccurate as to be worthless. Next time, cool the same to 90 degrees or less, and then take the reading and use the correction software or tables to correct it.

__________________
Broken Leg Brewery
Giving beer a leg to stand on since 2006
Yooper is offline
 
Reply With Quote Quick reply to this message
Old 03-07-2013, 03:31 AM   #6
TahoeRy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2012
Location: South Lake Tahoe, California
Posts: 305
Liked 43 Times on 35 Posts
Likes Given: 2

Default

I will try that next time. I was not aware of that. I always thought I could correct using those charts at any temp. I bet my pre-boil gravities are all over the place then as I usually take my pre-boil gravity between 125 and 150 prior to lighting my burner. My FG's are always on-point with my expected efficiency, as this one was, but those are taken at around 70 - 75 degrees and usually only correct up a point or two at most.

Thanks for the replies!

__________________
TahoeRy is offline
 
Reply With Quote Quick reply to this message
Old 03-08-2013, 12:49 AM   #7
jmh286
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
jmh286's Avatar
Recipes 
 
Join Date: Oct 2012
Location: Port Wentworth, GA
Posts: 173
Liked 16 Times on 14 Posts
Likes Given: 7

Default

Quote:
Originally Posted by TahoeRy View Post
I will try that next time. I was not aware of that. I always thought I could correct using those charts at any temp. I bet my pre-boil gravities are all over the place then as I usually take my pre-boil gravity between 125 and 150 prior to lighting my burner. My FG's are always on-point with my expected efficiency, as this one was, but those are taken at around 70 - 75 degrees and usually only correct up a point or two at most.

Thanks for the replies!
For future reference, FG is Final Gravity, meaning the gravity after fermentation. You are measuring OG or Original Gravity after the boil. I highly recommend a refractometer for Pre/Post-Boil Readings. It requires a few drops and cools down much faster. You can find a halfway decent one on Amazon for ~40 bucks.
__________________

Mmmmmmm...Beer

jmh286 is offline
 
Reply With Quote Quick reply to this message
Old 03-08-2013, 12:58 AM   #8
TahoeRy
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2012
Location: South Lake Tahoe, California
Posts: 305
Liked 43 Times on 35 Posts
Likes Given: 2

Default

Duh.... Wow you got me on that one. Total foot in the mouth. You are correct. My title is kinda obvious right. My FG better be lower than my pre-boil gravity. I guess I was so perplexed by my issue half my brain shut off. I am glad I at least got some helpful advice that I think will give me more of an accurate gravity reading. For a guy that's been brewing for 16 years you think I would of instinctively known not to type FG for my OG. Oh well. Funny, I didn't even notice it until you mentioned it.

__________________
TahoeRy is offline
 
Reply With Quote Quick reply to this message
Old 03-08-2013, 01:01 AM   #9
duboman
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2011
Location: Glenview, IL
Posts: 6,032
Liked 459 Times on 426 Posts
Likes Given: 207

Default

I will use a hydomter, fill the tube and stick it in the freeze for a bit while the wort comes to boil, in about 15 minutes the sample will usually cool to below 95 and good to read.

I'm not a fan of adding dME but I will boil longer to get my post boil OG and just have a little less beer if necessary.

__________________
Nothing Left to do but smile and drink beer.....

The Commune Brewing Company-Perfecting the "art" of beer since 2010
duboman is offline
 
Reply With Quote Quick reply to this message
Old 03-08-2013, 01:09 AM   #10
beernbourbon
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
beernbourbon's Avatar
Recipes 
 
Join Date: Jan 2013
Location: Cincinnati, Ohio
Posts: 114
Liked 28 Times on 24 Posts
Likes Given: 46

Default

Quote:
Originally Posted by Yooper View Post
Remember that even with temperature correction tables, any SG sample over about 90 degrees is inaccurate- so inaccurate as to be worthless. Next time, cool the same to 90 degrees or less, and then take the reading and use the correction software or tables to correct it.
Been brewing a while, first post here.... I'm kinda confoozed.... this is the first time I've heard of the gravity reading being inaccurate over 90*. So, whyfore the tables/calculators give the numbers? I thought that was the point of the tables/corrections calculators? Understand, I'm just trying to figure it out, since I take constant readings, pre-boil, post-boil, as soon as I get the wort in the fermentor I'm checking, then when the Krausen starts to fall, I start checkin' n tastin'.....and when I'm not doing stupid things like sparging with water at the completely wrong temp, or adding a gallon more water than I'm supposed to... I usually hit my numbers pretty close. (at least now...lol...a while ago...yeah, not so much)
__________________

beer and bourbon....no other liquids necessary

beernbourbon is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Og Lower then Pre Boil gravity. 355Newell All Grain & Partial Mash Brewing 13 02-09-2013 01:12 AM
1st running gravity vs pre boil gravity vs post boil gravity TTB All Grain & Partial Mash Brewing 3 12-07-2012 06:55 AM
Hitting Pre-boil gravity, missing Post-boil gravity jbags5 Beginners Beer Brewing Forum 20 09-29-2012 01:41 PM
Post boil gravity lower than pre boil PolarisSnT All Grain & Partial Mash Brewing 10 06-15-2011 08:04 PM
how can I determine post-boil gravity from a pre-boil gravity reading? snailsongs General Techniques 5 03-05-2009 03:42 PM



Newest Threads