Porter OG Pre-Boil vs. Post Boil Issues

[theashman661]

Yesterday I brewed a Porter/ In the recipe once punched into beersmith, it called for 1.049 pre-boil and 1.065 post. I was at a 1.047 pre boil, Which I thought was a pretty good mash efficiency. But when it came to the post 90 min boil, I was only at 1.056. I was 9 points off and that doesn't seem to successful. My boil was vigorous and once I filled up my carboy, I was right at the 5 gallon mark, so If Boiled harder, or for longer I would have come up short on the volume. So I know that the beersmith accounted for all the correct evaporation, so I feel that my boil was right on target, volume and evaporation wise. Anything that anyone see's or has had the same issue with before. I'm not worried about it too much, but just want to know why and what I can do next time to avoid this discrepancy. Thank you!

 

[porterpounder]

Was carboy mixed thoroughly before sampling and was the temperature of the sample ideal? With a vigorous 90 minute boil, you're pretty much guaranteed to boil off about 15 gravity points. I'd blame the measuring equipment or the sample method.

 

[MindenMan]

theashman661, what was your pre-boil volume? We can help you better if you will answer that for us.

 

[Yooper]

For your preboil reading, did you cool the wort to under 90 degrees before using a hydrometer? Or, if using a refractometer, is the refractometer calibrated with distilled water?

It's not possible that both SG readings are right, if you boiled off the proper volume. So, either the reading is wrong or the volume was incorrect for the preboil readings.

 

[theashman661]

theashman661, what was your pre-boil volume? We can help you better if you will answer that for us.

Apporx. 6.5- 6.75 gallons

 

[theashman661]

Was carboy mixed thoroughly before sampling and was the temperature of the sample ideal? With a vigorous 90 minute boil, you're pretty much guaranteed to boil off about 15 gravity points. I'd blame the measuring equipment or the sample method.

I stirred the crap out of the wort, and even dumped into my bottling bucket to aerate a little more before dumping into carboy. and it was around 85 degrees when I last took a measurement, plus I used the refractometer.

 

[theashman661]

For your preboil reading, did you cool the wort to under 90 degrees before using a hydrometer? Or, if using a refractometer, is the refractometer calibrated with distilled water?

It's not possible that both SG readings are right, if you boiled off the proper volume. So, either the reading is wrong or the volume was incorrect for the preboil readings.

The refract was calibrated with distilled water about 2 moths ago. I will re-calibrate tonight and see if it is off.

I will double check my volume as I remember where it was at when the boil first started, around 2" from top of kettle. I will see if maybe I sparged a little too much water and had a high pre boil volume. However after 90 min. and a loss of .5 gallon in trub, I came in at exactly 5 gallons. So I think that the water volume was right on. I will confirm however.

ALSO: I used brew 365 to calc. Sparge/mash water volumes. For some reason in beer smith the volumes never match up to what I really need. I have set up the proper, evap, trub, equipment loss, and mash ton loss, etc. But still never seems to calc out the same as 365. One of the programs is lying to me!!!!

 

[theashman661]

I would like to also add the following:

6.75 gallons of 1.045 pre boiled wort
Boiled 90 min:
~5.5 gallon post boil of 1.056...

By my calcs, this is what it should be. The Stone recipe says it should be 1.65?

http://www.notsoprofessionalbeer.com/2011/09/stone-smoked-porter-homebrew-recipe.html

 

[acidrain]

So you only boiled off 1 gallon in 90 minutes? I boil off 2 gallons in 1 hr.
Are you using Beersmith? If so, have you accurately entered your equipment profile?
I see two things here;
1) It's impossible to have boiled off a measured amount from a measured starting point and come up short in gravity points. Either you measured the beginning or ending (or both) volumes wrong, or the SG's wrong.
2) If your recipe is based on a a certain equipment, which you are not using, the efficiencies and losses will not jive with your actuals.

You need to know (accurately) what your beginning volume was, what your ending volume was, and what both SG's were. Then you can compare that to the grainbill and figure out your efficiencies.
The mash efficiency is important because it's nice to know how much conversion you got, and the brewhouse efficiency is good because your need to know that your starting gravity is within the style. The actual amount that goes into the fermenter is of less importance, but if you know your trub and kettle losses, you can dial that into Beersmith and make up for major brewhouse inefficiencies by adding more or less grain and volume as needed.

 

[theashman661]

So you only boiled off 1 gallon in 90 minutes? I boil off 2 gallons in 1 hr.
Are you using Beersmith? If so, have you accurately entered your equipment profile?
I see two things here;
1) It's impossible to have boiled off a measured amount from a measured starting point and come up short in gravity points. Either you measured the beginning or ending (or both) volumes wrong, or the SG's wrong.
2) If your recipe is based on a a certain equipment, which you are not using, the efficiencies and losses will not jive with your actuals.

You need to know (accurately) what your beginning volume was, what your ending volume was, and what both SG's were. Then you can compare that to the grainbill and figure out your efficiencies.
The mash efficiency is important because it's nice to know how much conversion you got, and the brewhouse efficiency is good because your need to know that your starting gravity is within the style. The actual amount that goes into the fermenter is of less importance, but if you know your trub and kettle losses, you can dial that into Beersmith and make up for major brewhouse inefficiencies by adding more or less grain and volume as needed.

Yeah something doesn't seem right. I need to take actual measurements tonight and see what I started at and what I ended at. I referenced some dings in my kettle that were my start and stop points. I will measure the water at those heights and see what we come up with. Thank you!. I will post the answers tomorrow and see if we can find out where I went wrong.

 

[kaconga]

I would like to also add the following:

6.75 gallons of 1.045 pre boiled wort
Boiled 90 min:
~5.5 gallon post boil of 1.056...

By my calcs, this is what it should be. The Stone recipe says it should be 1.65?

http://www.notsoprofessionalbeer.com/2011/09/stone-smoked-porter-homebrew-recipe.html

You found the problem. A 1.049 @6.75 gallons won't get you to a 1.065 @ 5.5 gallons. So either you were supposed to boil longer or a number was off somewhere. For the volumes stated you would need to have started at 1.053. Hope that helps.

 

[theashman661]

You found the problem. A 1.049 @6.75 gallons won't get you to a 1.065 @ 5.5 gallons. So either you were supposed to boil longer or a number was off somewhere. For the volumes stated you would need to have started at 1.053. Hope that helps.

If you take a look at the recipe, it calls for 6.75 gallon to boil for 90min. When I punch everything into beersmith, it called for a pre boil of 1.049 which mine was 1.045, not too bad. So in 90 min boil I should have boiled off way more than 1.25 gallons? I'm in So-Cal and it was super hot yesterday and also humid (Well Humid for California). Maybe that was what happened?

What is the average boil off loss in volumes for a 90 min boil, and a 60 min boil? Just to see if my boil off rate is keeping up... thanks

 

[acidrain]

If you take a look at the recipe, it calls for 6.75 gallon to boil for 90min. When I punch everything into beersmith, it called for a pre boil of 1.049 which mine was 1.045, not too bad. So in 90 min boil I should have boiled off way more than 1.25 gallons? I'm in So-Cal and it was super hot yesterday and also humid (Well Humid for California). Maybe that was what happened?

What is the average boil off loss in volumes for a 90 min boil, and a 60 min boil? Just to see if my boil off rate is keeping up... thanks

There is no average... there is only YOUR boil off rate.
I suggest the following;
carefully pour measured amounts (1/2 gallon increments?) of water into your boil kettle and mark on your stir spoon or kettle each addition.
Fill your kettle with exactly 5 gallons of water and begin boiling.
Once the water comes to a rolling boil, begin the clock.
After 1 hour, kill the heat and measure the volume.
Note the difference as boil off per hour rate.

 

[MEPNew2Brew]

I have had similar issues in the past. It seems that a few relatively minor items can add up to a pretty big impact post - boil. First, I find it extremely difficult to get good, accurate volume measures. I use graduated 5 gallon buckets (Brewer's Best, if I recall correctly) to measure my wort volumes for the most part, plus a stick marked that I put in the brew kettle. None of that is very accurate. I have started using just one bucket to measure, so at least my measurements are consistent, even if not correct.

Second, if sometimes you measure volume with the wort cold and sometimes hot, you can have difference volumes. BeerSmith can correct for this. But, you have to set the correction correctly. This issue can be particularly important when determining your initial boil off rate. Let the post boil water cool before measuring the volume.

Just my two cents.

 

[MindenMan]

If you had 6.75 gallons of 1.047, and you reduced it to 5.5 gallons would give you 1.058. Something in your readings is off, I believe.
Did someone else already say this?

 

[kaconga]

K. So some quick math: 49*6.75=330.75
330.75/5.25=63
So based on those two calculations we can see that beersmith was planning on boiling off 1.5 gallons of water.
On to the real world:
45*6.75=303.75
303.75/5.5=55.2
So the problem became compounded by not getting the boil off predicted and not hitting the pre boil gravity. TYPICAL boil off rate is 1 gallon/hr. However that will vary with a whole host of factors. So you need to determine your boil off rate and use that over the typical rate whenever you can. Ideally, imo, you would always boil off a tad more vs a tad less as it is easier to top off then boil off more once the wort is chilled.

 

[theashman661]

Ok, so I went home last night and marked a pvc pipe and did it in 1 gallon increments. I must have goofed on my sparge calculator, because I had around 8 gallons of pre boiled wort at 1.047. After 90min boil I was 5.5 gallons of 1.055. So after doing my calculations, this was correct. I over sparged and collected too much wort. Had I only collected 6.75 gallons, It may have been at 1.53, where my preboil should have been. So I need to hit the drawing board and figure all my mash tun loss, boil off rate, and evaporation rate a little more closely. This is a very important step that I have been pushing off. Thank you all for your help and ideas in this matter.