Post boil SG HELP!!!

[Will2233]

Hi, I am about to pull my hair out with the the problem I'm having with my Robbobrew 35 L.
My pre boil SG is right on the money using either Beersmith or Brewfather, but my post boil is always at least 4-6 points low.
Its doing my head in, todays brew was a Sierra Nevada based recipe with a 90 minute boil.
My volume after sparge was right and pre boil SG was right but the post boil SG was down 6 points.
Any suggestion would be gratefully accepted.
I am using Gash's profile in Beersmith for the Robbobrew 35L. Recipe attached.
William

 

[Half-baked]

The obvious answer is that you’re boiling off less than you anticipate.

The amount of sugar in the kettle doesn’t change, or to put it another way, the total number of gravity points remains the same.

For example, if you have 25l of 1.040 wort, that’s a total of 1000 gravity points. Boil off 5l and you are left with 1000/20 = 50 (50 points is a gravity of 1.050).

Another possibility is measurement error. Are you using a refractometer? Hot wort, or wort with trub, will tend to give you a lower reading than accurate. To take a reading, draw off a sample from kettle, cool, draw clear wort into pipette then take the reading.

If it’s a hydrometer, make sure you cool to the calibration temp.

 

[Will2233]

The obvious answer is that you’re boiling off less than you anticipate.

The amount of sugar in the kettle doesn’t change, or to put it another way, the total number of gravity points remains the same.

For example, if you have 25l of 1.040 wort, that’s a total of 1000 gravity points. Boil off 5l and you are left with 1000/20 = 50 (50 points is a gravity of 1.050).

Another possibility is measurement error. Are you using a refractometer? Hot wort, or wort with trub, will tend to give you a lower reading than accurate. To take a reading, draw off a sample from kettle, cool, draw clear wort into pipette then take the reading.

If it’s a hydrometer, make sure you cool to the calibration temp.

Thanks for your reply Half-baked,
I can only assume I must be doing something wrong with the refractometer.
It seems strange that my pre-boil SG is on the money but drops after boil.
Ill have to double check with my hydrometer the readings I get when doing my next brew.
I'll post how I get on.
William

 

[David B]

Hi, I am about to pull my hair out with the the problem I'm having with my Robbobrew 35 L.
My pre boil SG is right on the money using either Beersmith or Brewfather, but my post boil is always at least 4-6 points low.
Its doing my head in, todays brew was a Sierra Nevada based recipe with a 90 minute boil.
My volume after sparge was right and pre boil SG was right but the post boil SG was down 6 points.
Any suggestion would be gratefully accepted.
I am using Gash's profile in Beersmith for the Robbobrew 35L. Recipe attached.
William

Hi - keen to get this recipe but cant open it in this format, assume BS. I am using BF and would appreciate you exporting in BF format if possible. thanks

 

[Will2233]

Hi - keen to get this recipe but cant open it in this format, assume BS. I am using BF and would appreciate you exporting in BF format if possible. thanks

Hi David B,
Hopefully recipe attached.
Converted from Beersmith.
I don't seem to be able to capture the final readings page.
I'll try and get it.
William

 

[Half-baked]

Here it is from the horse’s mouth:
https://sierranevada.com/blog/pale-ale-homebrew-recipe/
Mash at 68c and ferment at 20c

38 IBUs and California ale yeast (us-05/wlp001/wyeast 1056)

 

[MHB]

Will - try the snipping tool if you are using windows.
You can capture a copy of anything on screen and just paste it straight into a post.
Mark

 

[chookherder]

[/QUOTE]

Hi, I am about to pull my hair out with the the problem I'm having with my Robbobrew 35 L.
My pre boil SG is right on the money using either Beersmith or Brewfather, but my post boil is always at least 4-6 points low.
Its doing my head in, todays brew was a Sierra Nevada based recipe with a 90 minute boil.
My volume after sparge was right and pre boil SG was right but the post boil SG was down 6 points.
Any suggestion would be gratefully accepted.
I am using Gash's profile in Beersmith for the Robbobrew 35L. Recipe attached.
William

Hi William,

Looking at the numbers you have populated into this recipe in the Session Data, it shows this:

Are these numbers correct,
PreBoil Vol = 29L and SG = 1.047
Post Boil Vol = 25L approx and SG = 1.044

Do you have a SG reading before you Sparge and the amount of volume of Sparge water you used?

To me it suggests the Refractometer readings are not accurate, (maybe both of them) but most likely the Pre-boil SG looks too high, 86.7% Mash efficiency in Robobrew is very very good.

I had a similar problem with my readings and found it was because my wort sample was not 20ºC when taking the readings, amazing how a few degrees can change those readings. My friend had skewed readings of his Pre-Boil SG from a Robobrew because he was drawing the sample from the bottom of the machine before the Sparge water had mixed through the wort.

Definitely the Hydrometer vs the Refractometer is the way to go next time.

Not sure this helps,
Ben

 

[chookherder]

For those that could not open the Beersmith file, attached are 2 exports of it. One as 'Recipe' style and one 'Brew Steps' style...

Cheers big beers.

 

[MHB]

Extract can’t evaporate in the kettle, you can physically lose some (leave in kettle, in lines, in boilovers...) but if it’s in the kettle at the start and you don’t loose any it will be there in at the end.

The other possibility remains that you aren’t measuring well. Do you stir you kettle full before sampling,, remembering that first runnings are going to be heavier than sparge, are the fully mixed. Are you taking a sample from a tap on the kettle, it might not be what we call a representative sample. Are the samples cooled to 20 or are you interpolating from a table, is your equipment accurately calibrated both for volume and temperature, measuring equipment calibrated?
It’s a fact of life that if you boil a wort, it will get denser! Most everything else comes down to bad processes or equipment.
Mark



And FFS don’t put any Carbonates in your sparge water, that’s just asking for more tannins.
M

 

[Will2233]

Hopefully using the snip tool works.
Beersmith session details.
Regarding the water additions I was using the Beersmith water calculator.
I admit I'm not sure what I'm doing with the water.
I will have to do another brew and take extra caution and take on board every ones suggestions.
William

 

[Will2233]

Hi,
Here is the Robbobrew profile I'm using.
I may as well lay all my faults out for help.
William

 

[MHB]

While you’re feeling exposed, how about giving us you grain bill, be nice to see if what you think you are getting is even remotely possible.

From what I have seen so far, I suspect you are getting a false high first reading, taps in the bottom of the kettle are notorious (especially if they are connected to a pickup tube) for giving this sort of error. Always stir thoroughly, take a cup (as is in coffee mug) of wort out of the tap pour it back in the top then take a sample for reading.
Hope it’s that simple.
Mark

 

[Half-baked]

Hi,
Here is the Robbobrew profile I'm using.
I may as well lay all my faults out for help.
William

The main thing that jumps out at me is your boil-off rate.

I factor in 3.3l/hr, that’s at 2400w, with the neoprene insulation, at sea level.

I’m not sure of the conditions that will get you to 4.3l/hr…

Edit: if you are getting 4.3l/hr, cut back your power and save a little $$$. 10% boil-off is more than enough, you're closer to 15%

 

[Will2233]

While you’re feeling exposed, how about giving us you grain bill, be nice to see if what you think you are getting is even remotely possible.

From what I have seen so far, I suspect you are getting a false high first reading, taps in the bottom of the kettle are notorious (especially if they are connected to a pickup tube) for giving this sort of error. Always stir thoroughly, take a cup (as is in coffee mug) of wort out of the tap pour it back in the top then take a sample for reading.
Hope it’s that simple.
Mark

Grain bill attached.
William

 

[Will2233]

The main thing that jumps out at me is your boil-off rate.

I factor in 3.3l/hr, that’s at 2400w, with the neoprene insulation, at sea level.

I’m not sure of the conditions that will get you to 4.3l/hr…

Edit: if you are getting 4.3l/hr, cut back your power and save a little $$$. 10% boil-off is more than enough, you're closer to 15%

I have adjusted the boil off rate to your suggestion.
I am 105 meters above sea level and also use the jacket.
William

 

[MHB]

5.020kg with a potential of around 77% means 3.8654kg of extract available in a perfect world.
You get 29L at 1.047 SG, from Mass extract = V*SG*oP we get 3.5676525kg in the kettle.
That’s 92% brewhouse efficiency, Ok it is possible but I suspect it’s a bit high.
Be interesting to see what the answer is, it’s usually one of those great Mr Simpson "Dope" moments when you spot it.
Mark

 

[Will2233]

OK, for those playing along at home.
Today I brewed a pacific ale.
I paid particular attention to the crush.
I adjusted my BH efficiency to 70%
My pre boil was 1.043. Estimated 1.041.
Post boil 1.044, estimated 1.048.
I double and triple checked all readings with refractometer and hydrometer with samples cooled to 20 degrees.
I will attach relevant screen shots.
The only thing I did wrong is I forgot to raise the mash temp. for mash out. To get the recquired post boil I boiled for 70 minutes.
Any advice accepted, maybe being .004 points out is all I can expect.
William

 

[Jayvan90]

OK, for those playing along at home.
Today I brewed a pacific ale.
I paid particular attention to the crush.
I adjusted my BH efficiency to 70%
My pre boil was 1.043. Estimated 1.041.
Post boil 1.044, estimated 1.048.
I double and triple checked all readings with refractometer and hydrometer with samples cooled to 20 degrees.
I will attach relevant screen shots.
The only thing I did wrong is I forgot to raise the mash temp. for mash out. To get the recquired post boil I boiled for 70 minutes.
Any advice accepted, maybe being .004 points out is all I can expect.
William

Hey William,

I have been using a guten 40L for about a year now and am getting very consistent 75+%BH efficiency EXCEPT when I use voyager/compass pale malt, for some reason my numbers are always out when I use it, usually between 65 -70%… could it be the diastatic power of the malt yielding lower conversions? I’m probably wrong and certainly not as knowledgeable as MHB on the subject but I have been wondering why this happens myself, to the point that I’m done persevering with that malt .

 

[Will2233]

Hi Jayvan90.
I did wonder about the grain yield. I am wondering if the grain I think I'm using is not the grain I am using.
I too had trouble with voyager malts and stop using them, which is a pity because I liked the story behind the brand.
I mentioned that to the LHBS and they got back to me and said the voyager malts were smaller and that caused problems with my crush.
William