How would you know?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
LarryC

LarryC

Well-Known Member
Joined
Jun 27, 2009
Messages
728
Reaction score
12
Location
San Diego, CA
I plan on brewing my first all grain batch weekend after next. I have been reading How to Brew and coincidentally listening to a podcast from Brew Strong on sparging. In the podcast Jamil says that if you don't achieve the high enough efficiency (between 60% and 80%) you can just add some light DME to the boil to achieve the OG you should have gotten for your recipe.

My question is, how do you know you have the pre-boil OG you are supposed to have? I read Bobby M's all grain primer (www.suebob.com/brew) and know I can calculate the expected gravity and then calculate my efficiency for my mash/sparge. But all the recipes I see have the after boil OG listed not the pre-boil value. Do I Just calculate the 100% value of the grain bill and if my pre-boil gravity is in the 60 to 80% range range feel satisfied or is there something else to look at?
 
Gravity Units.

Gravity Units = (# gallons) x (last two digits of gravity)

Example: If pre-boil, you have 6.5 gallons of wort that is 1.045, you would have 292.5 gravity units (6.5 x 45). Then after the boil when you have reduced to 5 gallons, you take the 292.5 gravity units and divide by 5 gallons to get a gravity of your final wort of 1.085.

Hopefully that makes sense.

So, if you take your recipe and calculate gravity units, you have a target. This will not change during the brewing process after the mash/sparge and any other adjustments (like the DME you speak of).

Example: If your recipe is 5 gallons of a 1.060 IPA, you would have 300 gravity units. If after your mash, you have collected 7 gallons of wort that has a gravity of 1.038, you know that you are on track to have a 1.053 beer (7 gallons x 38 = 266 gravity units. Then 266 gravity units / 5 gallons = 53). At that point, you are missing 34 total gravity units (your target of 300 minus the 266 you currently have).

Each pound of DME is going to give you approx 45 ppg or 9 points for a 5 gallon batch. So, take those 34 points (for the full batch; in this case 5 gallons) you needed and divide it by 9 points and you will realize you need 3-4 lbs. of DME to make up the extra points.

I'm kind of drunk right now, but hopefully that makes sense

BTW - Every brewer should read Designing Great Beers by Ray Daniels - It covers this concept as well as many others a lot better than I probably just did
 
I'm not drunk and that made perfect sense to me.

Thanks for the clear answer (and have another brew on me)!

By the way, I haven't read the book you mentioned but I have read Palmer's how to brew and Brewing Classic styles. Seems like the more I read the more I find I still need to learn.
 
Designing Great Beers does a great job of explaining fairly simple "brewing math" and then gives guidelines for brewing to style. Palmer's and Jamil's are both great too.
 
Grizzlybrew said:
Gravity Units.

Gravity Units = (# gallons) x (last two digits of gravity)

Example: If pre-boil, you have 6.5 gallons of wort that is 1.045, you would have 292.5 gravity units (6.5 x 45). Then after the boil when you have reduced to 5 gallons, you take the 292.5 gravity units and divide by 5 gallons to get a gravity of your final wort of 1.085.

Hopefully that makes sense.

So, if you take your recipe and calculate gravity units, you have a target. This will not change during the brewing process after the mash/sparge and any other adjustments (like the DME you speak of).

Example: If your recipe is 5 gallons of a 1.060 IPA, you would have 300 gravity units. If after your mash, you have collected 7 gallons of wort that has a gravity of 1.038, you know that you are on track to have a 1.053 beer (7 gallons x 38 = 266 gravity units. Then 266 gravity units / 5 gallons = 53). At that point, you are missing 34 total gravity units (your target of 300 minus the 266 you currently have).

Each pound of DME is going to give you approx 45 ppg or 9 points for a 5 gallon batch. So, take those 34 points (for the full batch; in this case 5 gallons) you needed and divide it by 9 points and you will realize you need 3-4 lbs. of DME to make up the extra points.

I'm kind of drunk right now, but hopefully that makes sense

BTW - Every brewer should read Designing Great Beers by Ray Daniels - It covers this concept as well as many others a lot better than I probably just did
Click to expand...

Thanks Grizzly, that made perfect scene to me also! Cut and pasted!
 
For the guy who is about to brew his first batch ever, there's an even easier way to do things.

Mash, boil, cool, add yeast.

Your hands will be full getting a handle on the main, important bits. You'll get a decent beer. Don't sweat the math and gravity till next time (at earliest!)
 
I disagree... I was pissed as hell at my first AG batch because I had just spent 6.5 hours trying to make an IPA, only to find out my OG was 1.044. If I had just taken a preboil reading, I would have known to add some DME.
 
Do you guys just throw your preboil wort sample in the fridge for a little bit or is there some sort of temp correction for the specific gravity of a wort at post mash temps??
 
I do both. I chill for a bit to get it down into the range where I can trust an adjusted reading.

Well, that was before I got a refractometer! Now I simply draw a tiny sample with a pipette, blow on it for few seconds, drop it on the refractometer and take a reading.

Having to chill a sample mess with drawing several ounces was what made me spend the $40 on a refractometer.
 
ya I will eventually get a refractometer, but right now I am just buying the basics needs as I am just getting into AG. I have a fridge in my garage where I will be brewing. I figger it will cool enough during the boil that I can add the DME with 10-15 left.

Are there any websites that have calculators for the temp conversion?
 
I tossed the pre-boil sample into the freezer last weekend... If you use a large enough container, and get the sample thin enough, it will cool quickly.

You can also use Beer Smith's calculator and enter your pre-boil gravity reading and it will give you the post boil OG you should hit... You can also enter in your starting volume (in the Boil Off section), your starting gravity, and then adjust the boil time until you get your final volume to match your goal. It will also give you the final gravity (or the OG for the recipe)... There are a lot of tools to help your process within Beer Smith... Ones that I didn't think I'd use, I'm starting to. Really worth the $21 for the license (for two computers you own)...
 
The only problem I foresee with this is I don't know how quickly my turkey fryer with aluminum pot is going to boil off
 
Before I got a refractometer, I used to put a small saucepan in the freezer during setup. Then when it was time to check preboil gravity I just pulled off 3-4oz of wort and swirled it around the frozen pot. It only takes about 3min to get down to a readable level.

Most turkey fryers can burn off at least 1gal per hour. Just plan to have a preboil volume of 7gal, and boil down to 6gal in 60min. I always check the boiloff rate halfway through to make sure I'm on target, and then raise or lower my flame depending.
 
I would use a good thermometer to keep track of the temperature and keep it as close to boiling as possible (212F)... +/- a degree or two won't kill you, but going too high will increase the rate of boil off. Better to have the lid on hand so that you can partially cover the pot to help regulate the temperature. I would also keep watch of how fast your volume is boiling off. Easiest way would be to have a spoon, or something, marked with gallon, or 1 or 2 quart increments so that you know where it's at.

How long of a boil are you planning?

It might be a good idea to do a dry run with your boil setup. That way you'll have a better idea of how fast it will go. If this is a fresh pot, you'll want to condition it anyway, so this would serve both purposes. It will let you see how much boils off in an hour, or how long it takes to boil of a quart (or two)... As per other threads, condition the pot above the highest level you expect to use it to (fill wise)... So, if you have an 32 quart pot, get it to 30 quarts (or 31 if you dare) and condition it... I did my 32 quart to 30 quarts, and it's working well... The inside will turn really dark, which is what you want... Go for a 30-60 minute boil time and you'll be all set come brew day.
 
kanzimonson said:
Before I got a refractometer, I used to put a small saucepan in the freezer during setup. Then when it was time to check preboil gravity I just pulled off 3-4oz of wort and swirled it around the frozen pot. It only takes about 3min to get down to a readable level.
Click to expand...

Now THAT'S a great idea... I'll have to give that a swirl next brew day... :D:mug:
 
Grizzlybrew said:
Gravity Units.

Gravity Units = (# gallons) x (last two digits of gravity)

Example: If pre-boil, you have 6.5 gallons of wort that is 1.045, you would have 292.5 gravity units (6.5 x 45). Then after the boil when you have reduced to 5 gallons, you take the 292.5 gravity units and divide by 5 gallons to get a gravity of your final wort of 1.085.
Click to expand...

This doesn't add up for me. What am I doing wrong? 292.5 divided by 5 gallons is 58.50. So wouldn't that be a gravity of 1.058? I assume that since you said you were a little drunk, that this is a typo. But for dummies like me, I need clarification! :D
 
Golddiggie said:
I would use a good thermometer to keep track of the temperature and keep it as close to boiling as possible (212F)... +/- a degree or two won't kill you, but going too high will increase the rate of boil off. Better to have the lid on hand so that you can partially cover the pot to help regulate the temperature. I would also keep watch of how fast your volume is boiling off. Easiest way would be to have a spoon, or something, marked with gallon, or 1 or 2 quart increments so that you know where it's at.

How long of a boil are you planning?

It might be a good idea to do a dry run with your boil setup. That way you'll have a better idea of how fast it will go. If this is a fresh pot, you'll want to condition it anyway, so this would serve both purposes. It will let you see how much boils off in an hour, or how long it takes to boil of a quart (or two)... As per other threads, condition the pot above the highest level you expect to use it to (fill wise)... So, if you have an 32 quart pot, get it to 30 quarts (or 31 if you dare) and condition it... I did my 32 quart to 30 quarts, and it's working well... The inside will turn really dark, which is what you want... Go for a 30-60 minute boil time and you'll be all set come brew day.
Click to expand...


I already seasoned my pot when I got it. Did a 60 min boil. didn't even think to monitor the boil off at the time. I have my spoon marked off for 3-8 gallons when placed in my pot. I'll just have to keep a close eye on it and learn my system as I go. I was going to shoot for a 6.5 gallon boil and hopefully boil down to 5.5.
 
kanzimonson said:
Before I got a refractometer, I used to put a small saucepan in the freezer during setup. Then when it was time to check preboil gravity I just pulled off 3-4oz of wort and swirled it around the frozen pot. It only takes about 3min to get down to a readable level.

Most turkey fryers can burn off at least 1gal per hour. Just plan to have a preboil volume of 7gal, and boil down to 6gal in 60min. I always check the boiloff rate halfway through to make sure I'm on target, and then raise or lower my flame depending.
Click to expand...

I like the this idea. Will try that. thanks. probably won't even need a freezer since it will probably be 32 degrees in my garage
 
Jason_Merritt said:
This doesn't add up for me. What am I doing wrong? 292.5 divided by 5 gallons is 58.50. So wouldn't that be a gravity of 1.058? I assume that since you said you were a little drunk, that this is a typo. But for dummies like me, I need clarification! :D
Click to expand...

kanzimonson said:
You're right, and he's obviously experiencing some drunken dyslexia.
Click to expand...

lol! It's true, it's true... I become lysdexic when I'm krund :D
 
Wow, this thread went in a bunch of different directions :D

Thanks for the tip on the chilled pan for cooling the sample - I'll definitely be using that one. And, it looks like I have more books to read.

Thanks all!
 
LarryC said:
Wow, this thread went in a bunch of different directions :D

Thanks for the tip on the chilled pan for cooling the sample - I'll definitely be using that one. And, it looks like I have more books to read.

Thanks all!
Click to expand...

yea good idea I am going to start doing that
 

Similar threads

kgranger
Low efficiency with malted corn
Replies
9
Views
1K
wsmith1625
wsmith1625
T
Mash Volume Higher than Boil Volume eHERMS
Replies
5
Views
541
Town9
T
Airborneguy
Interesting Efficiency Issue
Replies
8
Views
466
DuncB
D
S
In search of...predictable mash efficiency for differing batch sizes & gravities
Replies
11
Views
724
Deadalus
Deadalus
Vladimir Kim
Low OG
Replies
6
Views
540
IslandLizard
IslandLizard
SSBrew 300

Latest posts

Back
Top