Re: help!! consistently low OG

Tue Jan 24, 2012 4:02 pm

Spider is dead on. You need the right setup for fly. Batch lets you really rinse all the grains.
the last thing that just occurred to me was what temperature are you taking gravity at? Technically gravity readings should be taken at 59 degrees. Your readings could be off there as well. Again brewing software can give you an adjusted og based on a higher temp.
I'll bet that's where your issue is. You probably had the right final gravity but if you checked it at a high temp it would appear too low.
kevindalyus
 
Posts: 19
Joined: Mon Feb 28, 2011 6:34 pm

Re: help!! consistently low OG

Wed Jan 25, 2012 6:27 am

One more thing that I didn't see mentioned in a quick re-read: have you checked your gravity with a good hydrometer also, or just with a refractometer?

Ignore me if this has already been addressed.
Fermenting: English Mild
Conditioning: Wild Pumpkin
Drinking: Funky Saison
User avatar
Cody
 
Posts: 267
Joined: Mon Feb 07, 2011 8:54 am
Location: MA

Re: help!! consistently low OG

Wed Jan 25, 2012 8:05 am

I do have a 10 gallon Igloo cooler with a SS braid. I am not sure off hand but the length is probably around 2.5 feet long and I have it wrapped around the bottom of the cooler. When I stir the mash, it comes up to the top of the cooler but it makes it way back down. Do you think it might get bunched up and cause the channeling issue you were talking about?

I have a refractometer with atc. And yes, I was just reading the gravity straight from the boil. I have learned and now, I take a dropper full of wort, then set it aside to read 20 minutes when it has cooled. I was using a hydrometer with all my mini mashes and my first two AG, but not recently. I have calibrated my refractometer.

As for the evaporation rate, I found an equation on byo.com from Mr. Wizard. Evaporation percent = 100 - (post-boil volume x 100 ÷ pre-boil volume). If I put my numbers in ER = 100 -(5.25x100 ÷ 6.5), I get a rate of 19.2%. Is that right? He does not take time of boil into account. Well anyway, that seems really high to me.


So the first and only book I read for brewing was Charlie P, The Joy of Homebrewing. Not that it isn't a good book. I just don't think it prepared me for AG. Therefore, I am in the middle of J. Palmer's How to Brew. Much better...
Last edited by megDC on Wed Jan 25, 2012 9:11 am, edited 1 time in total.
megDC
 
Posts: 19
Joined: Tue Sep 13, 2011 8:50 am
Location: Nebraska

Re: help!! consistently low OG

Wed Jan 25, 2012 9:04 am

megDC wrote:I do have a 10 gallon Igloo cooler with a SS braid. I am not sure off hand but the length is probably around 2.5 feet long and I have it wrapped around the bottom of the cooler. When I stir the mash, it comes up to the top of the cooler but it makes it way back down. Do you think it might get bunched up and cause the channeling issue you were talking about?


Yes, I do. If part of your braid is elevated off the bottom of the cooler, your sparge may be channeling to that spot and leaving wort below it behind (or at least not fully rinsed). Or if it ends up off to one side, you'll be channeling to that side and leavign the other side less rinsed. Palmer has a good discussion of channeling and different mash tun configurations in HtB. I'd say either find a way to keep it down, or try batching.
Spiderwrangler
PFC, Arachnid Deployment Division

In the cellar:
In the fermentor: Belgian Cider
In the works: Wooden Cider
User avatar
spiderwrangler
Global Moderator
 
Posts: 4663
Joined: Thu Jun 03, 2010 2:09 pm
Location: Ohio

Re: help!! consistently low OG

Wed Jan 25, 2012 9:10 am

[quote="ajdelange"]To find your true efficiency you do the following
1. Measure the volume and temperature of the wort (assuming that it is at this point that you wish to know the efficiency).
2. Correct the volume to room temperature
3. Meaure the specific gravity of the wort.
4. Multiply that by 0.998203 to get the density of the wort.
5. Multiply that by the volume of the wort to get the weight of the wort.
6. Convert the specific gravity to the equivalent °P. ( °P = -616.868 + 1111.14*SG -630.272*SG*SG + 135.997*SG*SG*SG)
7. Multiply the weight of the wort by °P/100. That is the weight of the extract
8. Divide by the total weight of the grain you mashed and multiply by 100.

A commercial brewery will get numbers in the high 70's. A home brewer does well if he gets numbers in the high 60's or low 70's.

This method gives you the pounds of extract per pound of grain - about as basic as you can get. Homebrewers typically complicate the process by assigning a "points per pound per gallon " number to each malt, working out the pounds per gallon for each malt, multiplying by ppppg and accumulating the points. They then compare that to the points from the SG reading for the wort. They call efficeincy 100*points_measured/points_calculated.[/quote]

To avoid confusion, I want to point out that the density conversion in step 4 (0.998203) is in kg/liter. To use this equation, make sure the wort volume is in liters and the weight of grain is in kg.
Alternately, you can substitute 8.33 lb/gal for the density conversion and use lbs of grain and gallons of wort.
Also, 80 or 81% is probably the maximum possible efficiency when using malted barley (the fine grind dry extract value) so a measured value in the 70's is pretty good.
Grandpa
 
Posts: 48
Joined: Fri Jun 20, 2008 11:45 am
Location: Santa Rosa, CA

Re: help!! consistently low OG

Mon Jan 30, 2012 8:20 am

I would just like to start by saying THANK YOU to all of you that replied.

I brewed yesterday and got my pre-boil and OG!!! I actually got the recipe numbers and bypassed my brew house efficiency of 60%. I did my first batch sparge and it worked out perfectly. It was also nice to brew in 57 degree weather instead of the 30s it has been all winter.

I am going to keep brewing every other week to get my set up with the batch sparge process down to a T. I also built and used my new hop filter with the paint strainer bag and that also worked superb.

I might head to Seattle for NHC this year. It will be my first time, anyone else going?
megDC
 
Posts: 19
Joined: Tue Sep 13, 2011 8:50 am
Location: Nebraska

Re: help!! consistently low OG

Mon Jan 30, 2012 3:59 pm

Yay, another batch sparge convert! :jnj
Spiderwrangler
PFC, Arachnid Deployment Division

In the cellar:
In the fermentor: Belgian Cider
In the works: Wooden Cider
User avatar
spiderwrangler
Global Moderator
 
Posts: 4663
Joined: Thu Jun 03, 2010 2:09 pm
Location: Ohio

Previous

Return to All Grain Brewing

Who is online

Users browsing this forum: No registered users

A BIT ABOUT US

The Brewing Network is a multimedia resource for brewers and beer lovers. Since 2005, we have been the leader in craft beer entertainment and information with live beer radio, podcasts, video, events and more.