Can anyone help me understand why my pre-boil and after-boil gravity are so bad?

We have used 11 lbs of bohemian pilsner and 1.1 lbs of CaraMunich II and according to the calculator we had 75% preboil efficiency but only 59% afterboil gravity.

Here is the recipe: http://www.brewtoad.com/recipes/cc16-cc8-clone

Our preboil gravity was 1.039 at 8.84 gallon wort and our afterboil gravity with a 1.54 gallon boil off (plus another gallon as trub, shrinkage, etc) was 1.042 at 6.3 gallons.

I like the preboil efficiency, but the afterboil is way to low. Is it supposed to be this low with 6.3 gallon final wort brewed from 12.1 lbs of malts?

Any thoughts on this?

By the way....this is a BIAB with 9.24 total water for mashing. No sparging at all.

Thanks a lot.

UPDATE: both the refractometer and the hydrometer are calibrated. I use them at room temp and if the wort is warmer I use a thermometer and correct the reading.
I take the OG reading just before I pitch and the wort is all stirred and aerated by then. I use a laddle to get wort from the middle of the fermentor.

What was the post-boil gravity temperature?

If it was 1.042 at, say, 150° that corrects to 1.061.

How did you measure gravity? Refractometer or hydrometer?

Elysium said:

We have used 11 lbs of bohemian pilsner and 1.1 lbs of CaraMunich II and according to the calculator we had 75% preboil efficiency but only 59% afterboil gravity.

Here is the recipe: http://www.brewtoad.com/recipes/cc16-cc8-clone

Our preboil gravity was 1.039 at 8.84 gallon wort and our afterboil gravity with a 1.54 gallon boil off (plus another gallon as trub, shrinkage, etc) was 1.042 at 6.3 gallons.

I like the preboil efficiency, but the afterboil is way to low. Is it supposed to be this low with 6.3 gallon final wort brewed from 12.1 lbs of malts?

Any thoughts on this?

By the way....this is a BIAB with 9.24 total water for mashing. No sparging at all.

Thanks a lot.

Click to expand...

Agreed, this does not make sense. Your gravity points, once introduced to the wort through the mash, can not be removed except by the yeast. This means that all you are doing during the boil is concentrating the wort which should increase your gravity. If you boiled off that much, you should have had more concentration.

Also, your trub loss is huge if you are planning on losing a gallon. I would highly recommend finding a way to reduce that.

Two questions to start:
When are you taking the readings in the process?
Are you compensating for temperature?

Boiling off that much should leave you with 1.055 wort (ish)

One more question to add to the list - did you stir the kettle before taking the pre-boil sample?

JackRussel said:

How did you measure gravity? Refractometer or hydrometer?

Click to expand...

both...11.8 refracto, 1.042 hydro (temp corrected)

LovesIPA said:

One more question to add to the list - did you stir the kettle before taking the pre-boil sample?

Click to expand...

Hm....actually I cant remember. I dont think I did.
So....that leaves me with the idea that my pre-boil efficiency is not even correct. Sad.

Foosier said:

Agreed, this does not make sense. Your gravity points, once introduced to the wort through the mash, can not be removed except by the yeast. This means that all you are doing during the boil is concentrating the wort which should increase your gravity. If you boiled off that much, you should have had more concentration.

Also, your trub loss is huge if you are planning on losing a gallon. I would highly recommend finding a way to reduce that.

Click to expand...

Trub is 0.8 gallon....then a bit of loss in the equipment and the shrinkage account for another 0.2 gallon I think.
I am not sure I understand you.....our preboil gravity from 1.039 goes to 1.042 afterboil gravity..that's normal. Boiling concentrates the sugar in the wort.

MrHadack said:

Two questions to start:
When are you taking the readings in the process?
Are you compensating for temperature?

Click to expand...

Yes....I correct the reading.
I take the reading once the mash bag comes out of the pot and then I take another reading before pitching.

geoffm33 said:

What was the post-boil gravity temperature?

If it was 1.042 at, say, 150° that corrects to 1.061.

Click to expand...

Agreed....with 75% afterboil efficiency, but I dont seem to have that.

LovesIPA said:

One more question to add to the list - did you stir the kettle before taking the pre-boil sample?

Click to expand...

Hm....actually I cant remember. I dont think I did.
So....that leaves me with the idea that my pre-boil efficiency is not even correct. Sad.

MrHadack said:

Two questions to start:
When are you taking the readings in the process?
Are you compensating for temperature?

Click to expand...

Yes....I correct the reading.
I take the reading once the mash bag comes out of the pot and then I take another reading before pitching.

Foosier said:

Agreed, this does not make sense. Your gravity points, once introduced to the wort through the mash, can not be removed except by the yeast. This means that all you are doing during the boil is concentrating the wort which should increase your gravity. If you boiled off that much, you should have had more concentration.

Also, your trub loss is huge if you are planning on losing a gallon. I would highly recommend finding a way to reduce that.

Click to expand...

Trub is 0.8 gallon....then a bit of loss in the equipment and the shrinkage account for another 0.2 gallon I think.
I am not sure I understand you.....our preboil gravity from 1.039 goes to 1.042 afterboil gravity..that's normal. Boiling concentrates the sugar in the wort.

what temperature is your hydrometer set for?

bajaedition said:

what temperature is your hydrometer set for?

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It shows 1.000 at room temp. I work at room temp all the time.

If the wort I am about to use with the hydrometer is at a different temp...then I just correct it using the information on the little slip that came in its protective tube.

Elysium said:

It shows 1.000 at room temp. I work at room temp all the time.

If the wort I am about to use with the hydrometer is at a different temp...then I just correct it using the information on the little slip that came in its protective tube.

Click to expand...

ok, then what temp is it set for?

bajaedition said:

ok, then what temp is it set for?

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I calibrated it at 25ºC (77F) temp...more or less. This is the average temp in my living room.

Right now it is 19ºC (66.2F). That's what the thermo shows.

I did the 2 point calibration with plain water and then with sugary water and it all looked good.

you cannot calibrate a hydrometer, it is already set

to get a true reading the temp of the sample needs to be that temp, not the temp of the room

so

what is the hydro set at?

I am trying to help, let us do this step by step

bajaedition said:

you cannot calibrate a hydrometer, it is already set

to get a true reading the temp of the sample needs to be that temp, not the temp of the room

so

what is the hydro set at?

I am trying to help, let us do this step by step

Click to expand...

Cool. Thanks.

Well, I guess it is called "calibration", but it is really doble-checking that the hydro meter work fine and the paper slip in it is where it should be for correct readings.

I do check the temp of the wort in the test tube and correct the reading according to it....so I am not sure that's the issue. I think my mashing process or something else has to be the culprit that lowers the efficiency.

Maybe the way I mill the grain (again.....I doubt this...during milling all the grains are coarse and open for perfect extraction of starches...and it is not too fine either). Maybe even the grain water ratio could cause problem. it is 1 lb/3 US quarts..

The only factor I can play with here is the efficiency...that's why I started to blame that. I mean 1.039 preboil and 1.042 afterboil are my "fixed" numbers and I calculated efficiency from that.

Then the other thing that puzzles me is the brix...
preboil brix is 10.4, which is according to the brewersfriend site is 1.041. Then the afterboil brix is 11.8 which is 1.047 according to the same site. Weird...really. Dunno what is happening and where the confusion/error come from.

I am not throwing rocks here, but something is way off. You need to calibrate your hydrometer to the prescribed temperature. Distilled water would be best, but tap water @ 60* F, should be dead on at 1.000. If your hydrometer is factory scaled to another temperature, use that instead. Pour in your sample as close to 60* F as possible, and read your hydro. That is what you really have. Please don't second guess your hydro, or your numbers will not ever be correct. "Room Temp" will always mislead you.

I just read your new post, and here is what I think, You cannot calibrate to one temperature, (other than 1.000) and then take your readings, and calibrate a calibration, to the calibration you have created by the non 60* F reading.

I just thought of a good example. 75% of 100, = 75. So then 10% of 100= 90. Now take 15% of 90, and you get 13.5. Add them together, and your answer is 23.5. By taking a percentage of a percentage, you get 23.5, not 25. I hope I said that right, and I am by no means trying to an as$, I, and some of the other posters are asking if you will try to formulate strictly by your hydrometer, not by recalibrating, and calibrating again.

If it is saying 1.000 at room temp, on the hydrometer, that means you are working in a 65F room? (Some are calibrated to 69 I think, or something like that). So what your post implies is you always keep your room as cold as the calibration temp on the hydrometer.

sablesurfer said:

If it is saying 1.000 at room temp, on the hydrometer, that means you are working in a 65F room? (Some are calibrated to 69 I think, or something like that). So what your post implies is you always keep your room as cold as the calibration temp on the hydrometer.

Click to expand...

MindenMan said:

I am not throwing rocks here, but something is way off. You need to calibrate your hydrometer to the prescribed temperature. Distilled water would be best, but tap water @ 60* F, should be dead on at 1.000. If your hydrometer is factory scaled to another temperature, use that instead. Pour in your sample as close to 60* F as possible, and read your hydro. That is what you really have. Please don't second guess your hydro, or your numbers will not ever be correct. "Room Temp" will always mislead you.

Click to expand...

Well, I think the room temp is totally irrelevant if one checks the temp of the wort and then corrects it to get the final reading. Or am I wrong?

By the way...the hydrometer instructions say it is meant to be used at 20C(68F)...but then again it is the liquid temp it talks about and I always check that and correct it.

minderman has a good post to read

hydros are usually set at 60 or 68 degrees, find what yours is set at then check it, it should read 1.000 at one of those degrees

we need to find if that hydro is set right to see if we are even comparing apples to apples, understand

now about efficiency, are you saying that you suspect that you are getting bad efficiency because of grain grind?, OK
After we are sure we are able to trust your hydro, We want to see about
your grind,
I suggest we get 5 pounds of 2 row, pre ground, bring it home and do a mash, 1.5 qts to a pound at 150 degrees
after an hour sparge it to your normal style of spargeing, collect 6 gallons
take a reading of it at whatever your hydro is set for. then boil off a gallon and take another reading.
both readings make sure the temp of the sample is at the setting of your hydro

this will be your base line sample. all test need a base line so we now have just established what a commercial ground malt will do with your system

now we do the same with 5 pounds of 2 row that you ground

now we can compare apples to apples

And work on it from there

Do you understand ?

Elysium, we are thousands of miles apart

so I am trying to make things as simple as possible

and I do not want to be doing correcting of readings, I want all readings done at the temp the hydro works at, that way we make no mistakes

I also want a base sample, a sample we know is an example we can refer back to all the time.

without these, we kind of are grasping for straws because we have nothing to refer to.

bajaedition said:

Elysium, we are thousands of miles apart

so I am trying to make things as simple as possible

and I do not want to be doing correcting of readings, I want all readings done at the temp the hydro works at, that way we make no mistakes

I also want a base sample, a sample we know is an example we can refer back to all the time.

without these, we kind of are grasping for straws because we have nothing to refer to.

Click to expand...

I'll work on these...I gotta get some sleep now. I cant really use my brain anymore.

Thanks a lot.

I think the grav readings may be ok especially since he says they tracked what he got on his refractometer.

I suspect the volume measurements may be the issue. Especially if the ore boil was hot wort and post boil was chilled.