confusing volumes and gravitys

[irishrover32]

i done a brew today, planned batch size was 3.5 gallons.
done my mash (BIAB) i hit my pre-boil gravity spot on 1.036 and my volume was 4.7 gallons which was .3 gallons over wat it should of been.
then i boiled for one hour, 5 minutes from the end of the boil i took a gravity reading with a refractomoter which i let cool to room temp which was 1.047 (12 brix).
then after cooling i came out with a gravity of 1.041 and a volume of 3.4 gallons

this makes no sense i checked all gravitys twice at room temp with a refractomoter and a hydromoter

from the boil off calculator i figured out that with this low a gravity i should of had just over 4 gallons

 

[masscarriers]

Out of curiosity, did you checked your pre-boil at sparge temps or you took a sample out to let cool?

 

[TopherM]

Was this all-grain, or extract?

If it's all-grain, this can be explained simply by higher efficiency, which could be something as simple as a finer crush on your grain.

If this is extract, then extract has a set efficiency. Assuming you get all of the extract into the boil, it is what it is, and won't change if you have the volume right.

Either way, a beer at 1.041 at 3.4 gallons is not far off from 1.036 at 3.5 gallons once you factor in that extra 0.1 gallons and a possible temperature correction on the hydrometer.

You are not far off either way.

 

[frazier]

You are right, something doesn't make sense. Let me see if I understand:

You started with 4.7 gal and a SG of 1.036. (Refractomer, hydrometer, or both??) This gives 169 gravity points.

Later, you had 3.4 gallons. Math would predict a SG of 1.049, so your 1.047 is not far off. Close enough for measurement errors, IMO. This was a refractometer measurement.

Then, you checked again with both instruments and got 1.041. So yeah, some of your measurements are wrong. Not sure which ones. The first two agree with each other, and the last two agree with each other, but something went haywire in between.

BTW, boiloff calculators are just guesses. Pay no attention to them. You get what you get on your own system.

Good luck,

 

[billl]

This probably isn't helpful at this point - but some of your measurements must be wrong. Boiling wort does not create or destroy sugar.

Did you leave any wort in the kettle? Was this a recipe with a ton of hops sucking up wort?

 

[irishrover32]

Out of curiosity, did you checked your pre-boil at sparge temps or you took a sample out to let cool?

i let all samples cool before taking measurements and all measurments were checked with hydrometer and refractomoter except the one i took 5 minutes from the end of the boil, i just used the refractomoter for that one.

Was this all-grain, or extract?

If it's all-grain, this can be explained simply by higher efficiency, which could be something as simple as a finer crush on your grain.

If this is extract, then extract has a set efficiency. Assuming you get all of the extract into the boil, it is what it is, and won't change if you have the volume right.

Either way, a beer at 1.041 at 3.4 gallons is not far off from 1.036 at 3.5 gallons once you factor in that extra 0.1 gallons and a possible temperature correction on the hydrometer.

You are not far off either way.

this was a BIAB brew, but it is a fair bit off going from 4.7 gallons at 1.036 to 3.4 gallons should give a gravity of around 1.048 thats why i cant figure it out it makes no sense, im 100% sure my pre boil gravity volume measurements where right i checked and double checked them numerous times at room temperature, i even checked them as they cooled and corrected the temperature.

You are right, something doesn't make sense. Let me see if I understand:

You started with 4.7 gal and a SG of 1.036. (Refractomer, hydrometer, or both??) This gives 169 gravity points.

Later, you had 3.4 gallons. Math would predict a SG of 1.049, so your 1.047 is not far off. Close enough for measurement errors, IMO. This was a refractometer measurement.

Then, you checked again with both instruments and got 1.041. So yeah, some of your measurements are wrong. Not sure which ones. The first two agree with each other, and the last two agree with each other, but something went haywire in between.

BTW, boiloff calculators are just guesses. Pay no attention to them. You get what you get on your own system.

Good luck,

your exactly right on all accounts, the thing thats tripping me up is why did i not come out with 1.049 it makes no sense its like the sugars just dissapeared

This probably isn't helpful at this point - but some of your measurements must be wrong. Boiling wort does not create or destroy sugar.

Did you leave any wort in the kettle? Was this a recipe with a ton of hops sucking up wort?

im 100% sure they're all correct there's no way my hydrometer reading and refractomoter reading could be both wrong yet both correlate with each other.

but i left a small amount of trub in the kettle id say around .05 gallons, and i did use a fair amount of leaf hops which sucked up some wort id say around .1 gallons at the absolute most.



could it be possible that i let my kettle and wort sit for a while to let the trub settle to the bottom and while doing this the sugars fell to the bottom and then i took my sample from the top which gave me a sample with very little sugars in it??

 

[billl]

"could it be possible that i let my kettle and wort sit for a while to let the trub settle to the bottom and while doing this the sugars fell to the bottom and then i took my sample from the top which gave me a sample with very little sugars in it??"

Not really. Once the sugar is in solution, it doesn't just settle out in a couple minutes.

I know you think there couldn't be anything wrong with your measurements, but something is (or there is something you are leaving out). It's not like your kitchen is immune from the laws of physics and chemistry.

Your only option are
1) volume measurement wrong
2) gravity measurement wrong
3) you lost some wort along the way

Also, you are starting measurements pretty surely. How are you measuring to 0.05 gallons? I'd usually assume at least a +/- 0.1 error rate in volume measurements. and +/- 1 point in gravity.

So min sugar of initial sample = 4.6*35 = 161
Max final sugar in kettle = (3.4+.2)*42=151

Still missing about 10 points or .2 gallons somewhere.

 

[irishrover32]

when i took the sample from the boiling wort with 5 minutes left, i used a spoon, there was some tiny bits of grain and trub in this sample. when i poured the sample onto the refractomoter i think some of the bits got onto the refractomoter could this effect the reading?

 

[billl]

when i took the sample from the boiling wort with 5 minutes left, i used a spoon, there was some tiny bits of grain and trub in this sample. when i poured the sample onto the refractomoter i think some of the bits got onto the refractomoter could this effect the reading?

no, the refractometer is just measuring how much the light bends as it travels through the liquid. It doesn't matter if there are bits in it.

 

[irishrover32]

then im out of theories, can anyone figure this out??? i just find it hard to believe my hydrometer and refractomoter could be giving the same incorrect figures.

 

[metalsniper]

My vote goes to volume measurement errors

 

[masscarriers]

could it be possible that i let my kettle and wort sit for a while to let the trub settle to the bottom and while doing this the sugars fell to the bottom and then i took my sample from the top which gave me a sample with very little sugars in it??

No definitely not, sugar is way too soluble to fall out of solution especially at high temperature. The problem is elsewhere I believe.

 

[pablosbrewing]

then im out of theories, can anyone figure this out??? i just find it hard to believe my hydrometer and refractomoter could be giving the same incorrect figures.

I'd chalk it up to a misread on refractometer at the 5 minute mark. 10.2Brix, not 12 Brix lines up with your final result.

For the volume loss:

Cooling shrinkage - you didn't actually start with 4.7 gallons.

Whole hop absorption can be a lot more than you think. Try weighing spent hops sometime.

How are you measuring to 0.1 gallons?