Quantcast

Gravity Readings?

Aussie Home Brewer

Help Support Aussie Home Brewer:

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
just put down my first batch of 120l on my new system. all went pretty well so im stoked. only thing is pre boil and OG.

normally on the 23l system i would pull normally around 1.038 pre boil and OG would be at around 1.043.

on todays first run i got 1.039 pre boil and after a hour boil ended with 1.040????
im guessing that if i finish with a FG at 1.010 then i have a around a 4% beer. i was hoping for more around 5%

can someone tell me why this is and what needs to be done for next brew?

cheers

hammo
 

goomboogo

Bring back Bum.
Joined
26/9/07
Messages
1,690
Reaction score
395
What was your pre-boil and post-boil volumes?
 

Wolfy

Well-Known Member
Joined
18/12/08
Messages
3,872
Reaction score
64
Location
Melbourne
just put down my first batch of 120l on my new system. all went pretty well so im stoked. only thing is pre boil and OG.

normally on the 23l system i would pull normally around 1.038 pre boil and OG would be at around 1.043.

on todays first run i got 1.039 pre boil and after a hour boil ended with 1.040????
...
can someone tell me why this is and what needs to be done for next brew?
The larger volume and likely different shape of boil vessel (less surface area per volume compared to smaller kettle) means there is less boil-off (and less % loss due to trube/cooling etc) so the wort does not concentrate as much in the kettle as it did for smaller batches.

All you need to do is get to know your new system a bit, and adjust your recipe as appropriate.
 

cam89brewer

Well-Known Member
Joined
2/10/11
Messages
559
Reaction score
0
The larger volume and likely different shape of boil vessel (less surface area per volume compared to smaller kettle) means there is less boil-off (and less % loss due to trube/cooling etc) so the wort does not concentrate as much in the kettle as it did for smaller batches.

All you need to do is get to know your new system a bit, and adjust your recipe as appropriate.
+1 as simple as that! After a couple more brews you'll get it perfect once you know how many litres per/hour of boil off and then just calculate with different recipes and different boil lengths.
 

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
thanks heaps for the feed back

24.5 kg grain

80l mash

pulled 59l

sparged 90l and pulled 85l

pre boil amount 144l @1.039

ended up with 115l wort after 1 hour boil @ 1.040

not sure how to bring it up to higher OG to get beer around 5%? how do i tweak the recipe or process?

cheers!
 

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
thanks heaps for the feed back

24.5 kg grain

80l mash

pulled 59l

sparged 90l and pulled 85l

pre boil amount 144l @1.039

ended up with 115l wort after 1 hour boil @ 1.040

not sure how to bring it up to higher OG to get beer around 5%? how do i tweak the recipe or process?

cheers!

post boil ended with 115l
 

tallie

Well-Known Member
Joined
2/2/09
Messages
637
Reaction score
62
pre boil amount 144l @1.039

ended up with 115l wort after 1 hour boil @ 1.040
This doesn't add up. I calculate that after boiling off 29L from 144L with a pre-boil of 1.039, your post-boil should be in the vicinity of 1.049 (144*39/115).

How confident are you with your measurements? in terms of volume, are you really seeing a 20% boil-off? Are you taking your gravity readings at the right temperature? Was the pre-boil wort evenly mixed?

Cheers,
tallie
 

bru

New Member
Joined
22/4/12
Messages
2
Reaction score
0
This doesn't add up. I calculate that after boiling off 29L from 144L with a pre-boil of 1.039, your post-boil should be in the vicinity of 1.049 (144*39/115).

How confident are you with your measurements? in terms of volume, are you really seeing a 20% boil-off? Are you taking your gravity readings at the right temperature? Was the pre-boil wort evenly mixed?

Cheers,
tallie
I can understand that this does sound a little mad but I have just started with a new rig (2nd brew in) and have experienced very similar results. I have 2 x hydrometers to ensure readings are accurate and on the 2nd brew I produced (this is pretty rough as from memory):

35L pre-boil at 1.039
28L post st 1.041

Any ideas?


Cheers
 

sponge

Dungeon O' Sponge Brewery
Joined
12/1/08
Messages
4,212
Reaction score
1,095
Something definitely doesnt add up...

35 * 39 / 28 = 48.75 (ie. ~1.049)

Should be getting a much higher post boil gravity than 1.041...


Sponge
 

QldKev

Brew Dude
Joined
21/6/05
Messages
7,471
Reaction score
1,031
Location
Bundy
Something definitely doesnt add up...

35 * 39 / 28 = 48.75 (ie. ~1.049)

Should be getting a much higher post boil gravity than 1.041...


Sponge

35 * 39 / (28 + plus trub vol) = ?


Say 2L trub
35 * 39 / (28 + 2) = 45 so getting closer

Depending on how much crap was stirred up initially in the wort up front, the initial reading could be higher than actual. Also were the samples cooled to a common temp?



QldKev
 

tallie

Well-Known Member
Joined
2/2/09
Messages
637
Reaction score
62
I can understand that this does sound a little mad but I have just started with a new rig (2nd brew in) and have experienced very similar results. I have 2 x hydrometers to ensure readings are accurate and on the 2nd brew I produced (this is pretty rough as from memory):

35L pre-boil at 1.039
28L post st 1.041

Any ideas?
Similar questions I had for hamstringsally:
How are you measuring volume? How accurate is it?
Also, are you measuring the volume in the kettle at the end of the boil, or what you transfer to fermenter? (sorry if that's a silly question, but could certainly explain it).
Are you measuring the gravity at the temperature that the hydrometers are calibrated at? (usually 20C)
Do the hydrometers read 1.000 .002 in tap water (again, at calibrated temperature)?
Is the wort evenly mixed when you take your pre-boil sample? (I'm presuming post-boil is mixed from boiling)

The calculations don't lie - if you are really losing 7L to evaporation, you are concentrating the wort by an inversely proportional factor, so at least one of those numbers is wrong (assuming same environmental constants).

As a guide, assuming your volumes and pre-boil gravity is correct, your post-boil should be
(35 * (1.039 - 1) / 28) + 1 ≈ 1.049

If your gravities and pre-boil volume is correct, your post-boil volume should be
35 * (1.039 - 1) / (1.041 - 1) ≈ 33.3L

Cheers,
tallie
 

ianh

Well-Known Member
Joined
24/10/08
Messages
690
Reaction score
99
Location
Wynyard Tassie
Are both your volumes measured at the same temperature or corrected for temperature. Water expands about 4% going from 20C to 100C.
 

bru

New Member
Joined
22/4/12
Messages
2
Reaction score
0
Hello Everyone, thanks for all your feedback!

I must be getting some of my measurements incorrect somewhere along the way.


To confirm I am gathering these measurements correctly.

I am taking pre-boil once boil tun is full and has been stirred.

Post-boil is taken after chilling and what is left in the boil tun including trub.


All hydrometer measurements are correct as have checked calibration and adjusted for temperature


I think I know the answer now, I have a calibrated dipstick with lines for volume measurements and I also had a mate giving me a hand, so I could be out by 5L on pre-boil which would slot it into about the correct levels after you have kindly provided all those figures.


Thanks again, I will be triple checking all measurements next time and may bring in an independent observer, maybe the UN have a few spares not working in Syria.
 

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
Similar questions I had for hamstringsally:
How are you measuring volume? How accurate is it?
Also, are you measuring the volume in the kettle at the end of the boil, or what you transfer to fermenter? (sorry if that's a silly question, but could certainly explain it).
Are you measuring the gravity at the temperature that the hydrometers are calibrated at? (usually 20C)
Do the hydrometers read 1.000 .002 in tap water (again, at calibrated temperature)?
Is the wort evenly mixed when you take your pre-boil sample? (I'm presuming post-boil is mixed from boiling)

The calculations don't lie - if you are really losing 7L to evaporation, you are concentrating the wort by an inversely proportional factor, so at least one of those numbers is wrong (assuming same environmental constants).

As a guide, assuming your volumes and pre-boil gravity is correct, your post-boil should be
(35 * (1.039 - 1) / 28) + 1 ≈ 1.049

If your gravities and pre-boil volume is correct, your post-boil volume should be
35 * (1.039 - 1) / (1.041 - 1) ≈ 33.3L

Cheers,
tallie
hey tallie,


cos ive only got 2 vessels i mash in one then take first runnings and put then into the fermenters till after i sparge and then put everything back into the boil pot. I measured out everything that went into boil pot before boil to see how much so i definatly know i started with 144l.

i stirred up and took a reading and temp would have been around 70 deg atm before boil to start my 60min and hop additions. at the time read 1.039

after hour boil i took OG reading at say 98 deg which came out at 1.040

So the more i think about it there could be a few reasons why it dosent add up that i can think of

1. different temps when taking readings?

2. I did not add (measure) what was left over in the bottom of the boil pot after boil which could be between 3 and 7l of hops ect (dont use hop bags) which i will do next time for the exercise. maybe this could be my novice mistake?

brew_house.jpg
 

sponge

Dungeon O' Sponge Brewery
Joined
12/1/08
Messages
4,212
Reaction score
1,095
I'd be investing in a refractometer for sure.

Taking only a couple of drops per sample which cool pretty much as soon they hit the refractometer lens and dont need to worry about temperature differences.

Can take reading at all stages of your brewing process, and costs <$50


Sponge
 

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
hey tallie,


cos ive only got 2 vessels i mash in one then take first runnings and put then into the fermenters till after i sparge and then put everything back into the boil pot. I measured out everything that went into boil pot before boil to see how much so i definatly know i started with 144l.

i stirred up and took a reading and temp would have been around 70 deg atm before boil to start my 60min and hop additions. at the time read 1.039

after hour boil i took OG reading at say 98 deg which came out at 1.040

So the more i think about it there could be a few reasons why it dosent add up that i can think of

1. different temps when taking readings?

2. I did not add (measure) what was left over in the bottom of the boil pot after boil which could be between 3 and 7l of hops ect (dont use hop bags) which i will do next time for the exercise. maybe this could be my novice mistake?
thanks so much for all the feedback. really helps and the more i look at it am making some novice mistakes!
 

hamstringsally

Well-Known Member
Joined
7/4/09
Messages
199
Reaction score
0
I'd be investing in a refractometer for sure.

Taking only a couple of drops per sample which cool pretty much as soon they hit the refractometer lens and dont need to worry about temperature differences.

Can take reading at all stages of your brewing process, and costs <$50


Sponge

hey sponge

i took my measurments with a refractometer

cheers
 

sponge

Dungeon O' Sponge Brewery
Joined
12/1/08
Messages
4,212
Reaction score
1,095
Interestinggggg.... I wouldve thought that youre errors may have been from temperature related issues.

Well then, I'll go sit back under my rock for a little bit.


Sponge
 

Latest posts

Top