Quantcast

Same pre boil reading every time.

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
So, to cut a long story short, my last several batches have all read the same pre boil gravity no matter what the grain bill.
I have mostly been doing no sparge on an all in one system and after hearing from the guys on Jim's beer Kit ( forum over here in the UK )
everybody says I must be measuring wrong or doing something wrong.
Tonight I have brewed a Stout with just a smidge over 6kg of grain.
I done this batch by sparging this time and guess what my pre boil gravity was....... 1.044, the same as all my other previous batches, so long as I have enough grain to at least get it to that point.
Anyhow my post boiler gravity is pretty much always about 2 points over pre boil even though I am boiling off over 4 litres of wort.
Everybody says it's impossible to have those reading, and I know that, they also say can't be an issue with my Hydro.
It reads 1.000 in water @ 20°c, however this evening I have noticed that the reading label inside the hydro is damp, so surely this would mean the hydro is cracked and would cause a lower reading? Any help would be MUCH appreciated.

Cheers
20201028_195754.jpg
 

Holden Caulfield

Well-Known Member
Joined
Apr 21, 2020
Messages
114
Reaction score
82
Any help would be MUCH appreciated.
Exactly what help do you need?

How to determine your efficiency and if it makes sense?
How to determine if you are measuring your preboil volume and gravity correctly?
How to determine if you are measuring your postboil volume and gravity correctly?
How to determine if your hydrometer is cracked (just test distilled or RO water and check if it reads 1.000)
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
What I'm asking is if anybody has had this issue?
My post boiler reading is 1.048, so apparently I have only gained 4 points for a 4.5ltr boil off?
Would moisture in the hydro mean there could be a crack and would that effect my readings?
As said previously, checked it in distilled water @20°c and it read 1.000.
I don't know if you can see in the pic as it's not the best, but a moisture line is quite visible around the 1.000 mark.
 

OldDogBrewing

Well-Known Member
Joined
Jun 11, 2020
Messages
298
Reaction score
209
What I'm asking is if anybody has had this issue?
My post boiler reading is 1.048, so apparently I have only gained 4 points for a 4.5ltr boil off?
Would moisture in the hydro mean there could be a crack and would that effect my readings?
As said previously, checked it in distilled water @20°c and it read 1.000.
I don't know if you can see in the pic as it's not the best, but a moisture line is quite visible around the 1.000 mark.
Are you correcting the temperature? Although it's still weird that you get the same readings, maybe the temperatures are varying accordingly to give you that result but what are the odds?
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
No I'm not correcting it, I am waiting for the sample to cool.
Sometimes the reading might be within 2 points of 1.044 but it nearly always hovers around that point. I must be doing something wrong but I just can't figure out what lol
 

Holden Caulfield

Well-Known Member
Joined
Apr 21, 2020
Messages
114
Reaction score
82
If your hydrometer is reading 1.000 with distilled it is still working. The moisture may be adhesive they use to affix the paper to the inside of the glass.

First let's baseline the situation:

Your preboil gravity is 1.044, at calibration temperature
Your postboil gravity is 1.046, at calibration temperature

What is your preboil volume?
What is your chilled post boil volume?

This information will allow us to determine how many you points you collected, and are the reasonable. Also, they should remain the same preboil to postboil.
 

bracconiere

Jolly Alcoholic
HBT Supporter
Joined
Jan 19, 2018
Messages
10,163
Reaction score
4,212
Location
S.AZ
what's the temp of your pre-boil sample? and that pic looks like 1.046 to me? some people use refractometers for OG and stuff, their only like $15. never tried one myself.
 

Calder

Well-Known Member
Joined
Mar 9, 2010
Messages
8,503
Reaction score
988
Location
Ohio
Do you use the same amount of grain, and water each time? Or the same ratio of water to grain?

Do you mix the wort before taking the reading? Are you taking the wort off the top?

A little more detail on your process including water volumes might help someone come up with something.

Depending on your water volumes you cold be reaching a point of diminishing returns; that is, As you add more grain, but not additional water, you may be losing efficiency that could offset the benefits of the additional grain. ....... but I don't know what you are doing, so this was just a guess.

If you are boiling off ~15% (I'm guessing at 4 liters out of ~29 liters leaving you 5 UK gallons), you would expect the gravity to increase a similar amount (will not be exact), so should move the gravity around 6 points.

If you don't trust your hydrometer, get another and see if you get the same results. I use a refractometer for all pre-boil measurements, and hydro for post fermentation. The refrac is really easy to use, it is not as accurate as a hydrometer (even with corrections) due to the different sugars in wort, but you should get readings within a point.
 

Holden Caulfield

Well-Known Member
Joined
Apr 21, 2020
Messages
114
Reaction score
82
A little more detail on your process including water volumes might help someone come up with something.
This says it all.

Very often when gravity targets (preboil, postboil, OG, FG) are missed the default is that something went wrong with the brewing process - bad crush, poor efficiency, ph of the wort, mash temperature, etc. Very often there is nothing wrong with the process, instead the missed numbers are with measurement of volumes or gravities due to wrong temperature, measuring FG with a refractometer without adjusting for alcohol, stratification of wort during lautering, human error, etc).

Before trying to solve a problem with the process that may not exist, the first step is to baseline the situation and determine if the preboil and postboil points match, because if they don't, there is clearly a measurement error and the problem may not exist, or is not solvable until accurate measurements are taken during the next batch.
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
I don't use the same amount of grain in each brew.
For this previous batch I used.

4.5kg Maris Otter
.5kg Malted oats
.5kg Choc Malt
.3kg Roasted Barley
.25kg Crystal

23 liter batch mashed with 20 litres of water and Sparged with 15.1 litres of water.
Mash P.H was 5.44.
All volumes were pretty much bang on, ended up with about 24 litres into fermenter with maybe 1liter left behind in the brewmonk.
All readings were taken @20°c.
My post boil gravity was 1.050 but was expected to be 1.058 based on 72% BHE.
 

Vale71

Well-Known Member
Joined
Nov 1, 2018
Messages
2,905
Reaction score
1,488
Is the cylinder too short and the hydrometer resting on the bottom?
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
Nope, it's a normal 100ml trial jar and the hydro is floating
 

Miraculix

Well-Known Member
Joined
Jun 4, 2017
Messages
3,500
Reaction score
1,984
Location
Bremen
I had hydrometers that where more off , the higher the gravity was. They read water correctly but the more sugar was involved, the more incorrect was the reading.

I figured this out by creating a defined sugar solution by weight. I looked up how many grams of sugar need to be in 100g of water to create a gravity of 1.1. or 1.06 or whatever suits you best. I then used my scale to create this solution and checked my hydrometer with it. The result was that the hydrometer was way off.
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
I will try this the sugar solution trick too see if this helps to explain if my hydro is off.
This is exactly what I was trying to say ( just not clear enough lol ) that my hydro could be off with more sugar in solution
 

Holden Caulfield

Well-Known Member
Joined
Apr 21, 2020
Messages
114
Reaction score
82
Anyhow my post boiler gravity is pretty much always about 2 points over pre boil even though I am boiling off over 4 litres of wort.
Everybody says it's impossible to have those reading, and I know that, they also say can't be an issue with my Hydro.
This is in fact not possible mathematically assuming a preboil in the 7.5 gallon range. If you boil off 1 gallon of wort from 7.5 you should see a change in gravity of about 15% . A 2 point change is only possible if the preboil gravity is around 1.015.

I don't use the same amount of grain in each brew.
For this previous batch I used.

4.5kg Maris Otter
.5kg Malted oats
.5kg Choc Malt
.3kg Roasted Barley
.25kg Crystal

23 liter batch mashed with 20 litres of water and Sparged with 15.1 litres of water.
Mash P.H was 5.44.
All volumes were pretty much bang on, ended up with about 24 litres into fermenter with maybe 1liter left behind in the Brew monk.
All readings were taken @20°c.
My post boil gravity was 1.050 but was expected to be 1.058 based on 72% BHE.
Just to confirm, in this case you saw a preboil gravity (1.044) to post boil gravity (1.050) change of .06, not .02.

Looks like Brew monk is an all in one system so the mash water and the lautering water is your preboil assuming homogenous mixing of sugars within wort and water absorbed by the grain (I think in gallons, so bear with me).

Preboil: 35.1 liters is 9.3 gallons x 44 PPG = 409 points
Post boil volume bottoms up: 24L into the fermenter + 1 liter left in Brew monk + water absorbed by grains .125 g/lb = 6.6 gal (25L) +1.66 gal (13.3LBs x .125) = 8.26. Which aligns with your boil rate. So post boil points are 8.26 x 50 = 413.

Your points check out, your volumes check out, and given your hydrometer is reading accurately when tested against distilled water you probably do not have a measurement issue (although your quote referenced at the top suggest that you do if you are consistently measuring only a 2 point drop with a 1 gal/hour boil rate).

I ran you recipe in my brewing program after setting it to reflect a Brew monk system and you should have been able to hit the 1.058 target gravity with a reasonable efficiency. In order to hit 1.050, the efficiency numbers have to be set very low. My process typically yields about 82% and I needed to set my program to 70% mash efficiency to achieve what you obtained. The math suggests you have an efficiency issue.

Most likely low efficiency reasons:
  1. Poorly crushed grains
  2. Channeling during lautering
  3. Incomplete starch conversion (mash temp to low, mash time to short)
  4. PH too high
Probably some others.
 
OP
M

MattGuk

Well-Known Member
Joined
Jan 23, 2012
Messages
292
Reaction score
53
Location
Oxford
Not sure yet as the beer isn't finished, took a sample last night and seems to be down to 1.012 and tasted really good.
My grain are always pre crushed so maybe I will start there.
P.H was 5.4 and the mash temp stayed at 66°c throughout the mash.
As for laurtering, I have no idea if it is channeling.
I guess I need to figure out how to increase my efficiency.
Previously I brewed BIAB which to me, all in one system are not that dissimilar. Only difference was I used fine crushed grain as the bad was a very fine mesh and wouldn't let too much grain through, so maybe as I have stopped asking for a fine crush, that could be the problem?
 
Top