Homebrewers Association | AHA Forum

General Category => General Homebrew Discussion => Topic started by: cheba420 on June 13, 2011, 04:30:09 AM

Title: Came up short!!!!!!
Post by: cheba420 on June 13, 2011, 04:30:09 AM
Looking for some insight here. I'm pretty sure I understand what happened, just not sure HOW it happened. I brewed an IPA today. My pre boil target gravity was 1062 and PB volume was supposed to be 7.5 Gallons. I was shooting for a 6 gallon batch into the fermenter. I wound up with a PB gravity of 1059 but had put 2 extra quarts of sparge water in the mash tun and wound up leaving it in the tun when I reached 7.5 gallons in the kettle. I assume that had I not used that extra 2 qts, I would have nailed my PB gravity. Oh well.

Heres the issue. I wound up with 4.75 gallons of wort into the fermenter. I left about a quarter gallon of cold break behind in the kettle. Since I started at 7.5 gallons and lost .25 gallons to the cold break in the kettle, this means that I boiled off 2.5 gallons in the 90 minute boil or 30% of the total volume. My boil was slow and steady. This was not an agressive boil by any means. Doesnt this seem excessive? My OG after cooling was 1072 which was my target which further confuses me. Seems like it would be a little higher than that since I concentrated my wort down to 4.75 G.

Any ideas here to get my evaporation under control? Or should I just be starting with more volume. Any pointers would be helpful.
Title: Re: Came up short!!!!!!
Post by: tschmidlin on June 13, 2011, 04:59:35 AM
You need to include the quart you left behind in your calculations, so it is 5 gallons at 1.072 to finish.  You can calculate the efficiency using 4.75, but for predicting the gravity after the boil, that 0.25 gallons counts.

That does seem like a lot lost for a 90 minute boil, I assume you are confident in your volume measurements?
Title: Re: Came up short!!!!!!
Post by: bluesman on June 13, 2011, 01:51:37 PM
How are you measuring your kettle volume?

2.5 gal of volume lost in 90 min equates to roughly 20% evaporation rate/hr. which is very high.
Title: Re: Came up short!!!!!!
Post by: weazletoe on June 13, 2011, 02:16:19 PM
Let's all just assume he's boiling with a Pratt & Whitney jet engine. Doesn't seem excessive then, does it?  ;D
 Now letys say it's a regular banjo burner.....What's the diameter of your pot, and how's the humidity where you live? I noticed when I moved from Ohio (which is typically like a rainforest) to Idaho (a desert) my evaporation has gone way up. I'm pushing the 20% mark. In fact, my last batch came in about 2 gallons shy of my 10. I need to make some changes to my calculations.
Title: Re: Came up short!!!!!!
Post by: narvin on June 13, 2011, 03:08:51 PM
What's the diameter of your pot, and how's the humidity where you live?

I'd look at these two factors... 20% is not necessarily high with a wide pot.

It's also not very useful to look at evaporation as a percentage, in my opinion.  For a given pot shape/size, you'll boil off the same volume in quarts whether the pot is holding 5 or 10 gallons, assuming the boil vigor is the same.
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 13, 2011, 03:22:29 PM
I think theres something else going on here.  You say you had 7.5gal of 1.059, that is 443 points of sugar.  You wound up with 5gal at 1.072, thats only 360 points.  You don't lose sugar from boiling.  Which means that one or the other of your volume measurements was off, or one of your gravity measurements.

Do you take into account the fact that grain absorbs 0.125gal/lb?  Maybe you didn't drain out 7.5gal in the first place.  For a grain bill to produce 7.5gal a 1.062 gravity wort you probably had around 17lbof grain right?  That means it on to held a little over 2gal of water.  I'm guessing you had 5.5gal preboil, making 4.5gal post-boil quite normal.
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 13, 2011, 03:46:21 PM
Sorry, Gentlemen. I guess I should have provided some more information. I use a standard turkey fryer type burner. My kettle is a sankey keg and I measured everything a couple of times yesterday because I didnt trust the numbers.

I have a measuring stick that I've marked for every half gallon in my kettle so, I know I had 7.5 g to start my boil. I'm in Phoenix, AZ and it was 100* yesterday...no humidity....but thats normal for this area. I measured my post boil volume with the marks that I have on the side of my carboy. So, I know theres accuracy there. My hydrometer is on point and I checked the temp of the sample. Again, on point.

Is this all evap? I've read several times that 9-12% is standard. Can my hot, arid weather be the culprit? I think Tomsayer has a very valid point. Seems as if something else might be off. I should have wound up putting 6 G in the fermenter and I only got 4.75. If you boil a wort down that low, shouldnt my OG been much higher due to the concentration??
Thanks for the replies.
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 13, 2011, 03:54:18 PM
7.5gal at 1.059 should produce 5gal at 1.088.  Since you volume meaurements were accurate, your gravity readings must have been off somehow.

How many pounds of grain was in your grist?  Do you know what your average efficiency runs?  That'd give us a clue as to which gravity measurement was off.
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 13, 2011, 06:10:32 PM
7.5gal at 1.059 should produce 5gal at 1.088.  Since you volume meaurements were accurate, your gravity readings must have been off somehow.

How many pounds of grain was in your grist?  Do you know what your average efficiency runs?  That'd give us a clue as to which gravity measurement was off.
Lennie, Thanks for the feedback. How did you go about calculating that? Its interesting and I think it would help me tremendously if I understood how you came to that equation.

Grain bill; was 18.37 lbs. My efficiency runs 65-70%. When I take my hydrometer samples, I cool them to 60-70* before I take the sample. My hydrometer is calibrated to read @ 60*. My sample was @ 70 so I added one point. PG gravity read 1058 and I added 1 to get 1059. At the end of my boil, I pulled another sample and cooled it down to 70* and it read 1072, I added 1 so 1073 with the temp adjustment.

I think it should also be known that I'm using beer smith. So, when I enter my recipe and the program tells me I should have 1059 pre boil and 1072 post boil and thats what I come up with BUT the final volume is shot.....Just not sure how to correct this and its pretty frustrating. Thanks for the help.
Title: Re: Came up short!!!!!!
Post by: bluesman on June 13, 2011, 06:32:31 PM
What's the diameter of your pot, and how's the humidity where you live?

I'd look at these two factors... 20% is not necessarily high with a wide pot.

It's also not very useful to look at evaporation as a percentage, in my opinion.  For a given pot shape/size, you'll boil off the same volume in quarts whether the pot is holding 5 or 10 gallons, assuming the boil vigor is the same.


Evaporation rates are useful for targeting final volumes per time unit and can impact energy consumption.

cheba420: How much water did you add to the mash tun? Have you recently calibrated your hydrometer? How much wort did you leave behind in the mash tun?
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 13, 2011, 06:57:57 PM
I do it as follows:  1.059 is 59 points per gallon (ppg, a measure of sugar per gal).  You had 7.5gal of this, 7.5 x 59 = 442 points total (the total amount of sugar in the pot).  Then you boiled and got 5gal, so the new ppg is 442/5 = 88ppg (back to sugar per gal).  This means the gravity post-boil should have been 1.088.  You got 1.073.  Boiling doesn't cause sugar to disappear sugar so some measurement is wrong.  If your hydrometer was not reading right, I suppose that could cause the discrepancy.

You had 18.4lb or grain.  18.4 x 36 points per pound per gallon (ppppg) is around 662 points of sugar.  I used 36ppppg just as an average for base malts and specialty grains.  We'll use the low end of your efficiency since big beers generally give lower efficiencies.  662 x 0.65 = 430 points.  Now divide by 7.5gal and you get  57ppg or 1.057.  Thats close to what you saw.  If we divide the 430 by 5gal, you'd have seen 86 ppg or 1.086, which is higher than your post-boil measurement.  This suggests your postboil gravity measurement was wrong.  Maybe you read it was 73 but it was really 83.

For your grain bill to match the post-gravity reading, you would have to have only gotten 55% efficiency.  This is certainly possible with a big beer since more grain holds more water and that water has sugar in it.  Plus you diluted with more water and didn't collect it (why? boil longer).  I don't know if you brew a lot of beers with gravities like this, if you know your efficiency is 60% for a big beer then recheck your gravity.

Can you tell I'm bored here at work?
Title: Re: Came up short!!!!!!
Post by: bluesman on June 13, 2011, 07:00:36 PM
Can you tell I'm bored here at work?

Really?  ;D :P
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 13, 2011, 07:57:04 PM
 
cheba420: How much water did you add to the mash tun? Have you recently calibrated your hydrometer? How much wort did you leave behind in the mash tun?
[/quote] Ron, I dont have my notes in front of me but I'd have to say it was 9.5 -10G. I accounted for the grain absorption. I have not calibrated my hydrometer. Didnt know you could. Just took that tool for what it was and trusted it. I assumed because its not mechanical, that it couldnt be adjusted. However, I now realize that it can be compensated for. Check it in plain water to get a read??? I left about 2 qts of wort in the tun.

I do it as follows:  1.059 is 59 points per gallon (ppg, a measure of sugar per gal).  You had 7.5gal of this, 7.5 x 59 = 442 points total (the total amount of sugar in the pot).  Then you boiled and got 5gal, so the new ppg is 442/5 = 88ppg (back to sugar per gal).  This means the gravity post-boil should have been 1.088.  You got 1.073.  Boiling doesn't cause sugar to disappear sugar so some measurement is wrong.  If your hydrometer was not reading right, I suppose that could cause the discrepancy.

You had 18.4lb or grain.  18.4 x 36 points per pound per gallon (ppppg) is around 662 points of sugar.  I used 36ppppg just as an average for base malts and specialty grains.  We'll use the low end of your efficiency since big beers generally give lower efficiencies.  662 x 0.65 = 430 points.  Now divide by 7.5gal and you get  57ppg or 1.057.  Thats close to what you saw.  If we divide the 430 by 5gal, you'd have seen 86 ppg or 1.086, which is higher than your post-boil measurement.  This suggests your postboil gravity measurement was wrong.  Maybe you read it was 73 but it was really 83.

For your grain bill to match the post-gravity reading, you would have to have only gotten 55% efficiency.  This is certainly possible with a big beer since more grain holds more water and that water has sugar in it.  Plus you diluted with more water and didn't collect it (why? boil longer).  I don't know if you brew a lot of beers with gravities like this, if you know your efficiency is 60% for a big beer then recheck your gravity.

Can you tell I'm bored here at work?
Lennie, Thanks for the breakdown. That is extremely helpful. I've heard a lot of people discuss gravity points but not in that context. Again, thank you. I cant say that my efficiency is any certain number with a big beer. I didnt really think of efficiency as fluctuating depending on og. Thats some food for thought as well. Sounds like I may have to check my hydrometer and see if thats the issue.

Theres another issue as well.....thats my boil off. The way I calculated it I get a 33% evap rate. Or 1.66 G per hour. That just cant be normal, even in Phoenix. Does this mean that I have to adjust my recipe as well as my mash/sparge water to end up hitting my targets??
Title: Re: Came up short!!!!!!
Post by: morticaixavier on June 13, 2011, 08:06:33 PM
to calibrate a hydrometer get some distilled water. that should read 1.000 at 60 degrees.

Title: Re: Came up short!!!!!!
Post by: tubercle on June 13, 2011, 11:29:15 PM
If the hydrometer is off shouldn't it be off the same throughout the scale if all else is constant (sample temp, etc...)?
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 13, 2011, 11:36:29 PM
You went from 7.5gal to 5gal in 1.5hr.  That is quite a bit but with a hard boil and a lot of surface area I would imagine its possible.  Or it could be an indication that you didn't have 7.5gal to begin with. ;P

Tubercle I thought about that, the readings would be off by the same value and the math wouldn't work out either.
Title: Re: Came up short!!!!!!
Post by: Will's Swill on June 13, 2011, 11:44:12 PM
I'm with the Weaz, I boil in a dry climate and it wouldn't be terribly unusual for me to lose 2.5 gallons in 90 minutes.  Especially for big beers where I'm trying to lose volume.
Title: Re: Came up short!!!!!!
Post by: bluesman on June 14, 2011, 01:15:54 AM
Boiling 2.5 gal or 33% of the wort off in 90 min is really not necessary, unless of course that's your ultimate goal. I think we all can agree it's possible to boil off at that rate, as it looks like it really happened, assuming his volumes are accurate. Evaporation rates can vary frm the desert to the swamps but can also be somewhat controlled by the energy applied.

A hydrometer should be calibrated using distilled or RO water at the original calibration temp which should be marked somewhere on the hydrometer scale.

I recommend taking accurate water/wort volume measurements into the mash tun and kettle. This will help you better understand your efficiency and also help target your pre and post boil gravity. In addition, I also recommend monitoring your boiloff rate in order to accurately target your volume post boil.

BTW...did you measure your mash pH?
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 14, 2011, 01:31:11 AM
Boiling 2.5 gal or 33% of the wort off in 90 min is really not necessary, unless of course that's your ultimate goal. I think we all can agree it's possible to boil off at that rate, as it looks like it really happened, assuming his volumes are accurate. Evaporation rates can vary frm the desert to the swamps but can also be somewhat controlled by the energy applied.

A hydrometer should be calibrated using distilled or RO water at the original calibration temp which should be marked somewhere on the hydrometer scale.

I recommend taking accurate water/wort volume measurements into the mash tun and kettle. This will help you better understand your efficiency and also help target your pre and post boil gravity. In addition, I also recommend monitoring your boiloff rate in order to accurately target your volume post boil.

BTW...did you measure your mash pH?
Ron,
No sir, I was not trying to boil off that much. I was trying to boil off about 1.5 G and figured I'd boil off about a gallon per hour. My boil was low and controlled. Would it be helpful to keep track of my boiling temp and keep it as close to 212 as I can. I would assume that if I have it up at 225* I'm going to boil off a lot more than I would at 225*
I'll calibrate my hydrometer tonight and see where that gets me. I always measure water into the tun and wort into the kettle accurately. Somehow, my calcs were off by 2 qts of sparge water. Noted. Wont be doing that again. (hopefully). I've been using 5.2 in my mash recently...so the PH should have been pretty dialed in but no, I didnt actually check it.
Title: Re: Came up short!!!!!!
Post by: tubercle on June 14, 2011, 01:40:15 AM
Would it be helpful to keep track of my boiling temp and keep it as close to 212 as I can. I would assume that if I have it up at 225* I'm going to boil off a lot more ....


 You can't get the temp above 212* under the perssure of 1 atmosphere. It doesn't matter if you are using a turkey frier burner or a Pratt & Whitney. Ain't gonna happen. You can increase the intensity of the boil but not the temp.
Title: Re: Came up short!!!!!!
Post by: bluesman on June 14, 2011, 01:49:40 AM
Considering that you live in Mesa, Arizona your evaporation rate will be higher than normal but if you keep the boil to a steady "rolling over" type action that should be plenty. As long as you are constantly exposing new surface (turning over) area of the wort during the boil you will be volatilizing the pre-cursers to DMS, encouraging maillard reactions, as well as generating melanoidins during the boil. This action will suffice, and you will also minimize the evaporation rate as well.
Title: Re: Came up short!!!!!!
Post by: bluesman on June 14, 2011, 01:50:10 AM
Would it be helpful to keep track of my boiling temp and keep it as close to 212 as I can. I would assume that if I have it up at 225* I'm going to boil off a lot more ....


 You can't get the temp above 212* under the perssure of 1 atmosphere. It doesn't matter if you are using a turkey frier burner or a Pratt & Whitney. Ain't gonna happen. You can increase the intensity of the boil but not the temp.

+1

Title: Re: Came up short!!!!!!
Post by: morticaixavier on June 14, 2011, 03:38:53 AM
you could get the temp a little over 212 with a strong sugar syrup. I don't know exactly how much above 212, not much I would guess but some
Title: Re: Came up short!!!!!!
Post by: Tristan on June 14, 2011, 05:50:58 PM
What temperature was the wort when you measured pre-boil volume?  For a long time I didn't realize what a difference this makes.  For example volume measures 5% higher at boiling than at room temperature. 

I always assume I'll have my burner going as soon as bottom of the boil vessel is covered with wort.  I know Beer Smith has a setting for "cooling lost percentage" under "Equipment."  I usually put this at 4-5% because I assume the wort will be quite hot when I measure volume (in the upper 100s/lower 200s).  I think this is 4% by default.

If you measured 7.5 gallons at high temperatures it would be less going into the fermentor in addition to how much you boiled off.  If measured near boiling it would actually be 7.125 gallons at room temperature. 

In your example, you still would have had to had a 20% boil off rate and measured your pre-boil at near boiling to get that kind of loss.
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 14, 2011, 05:55:25 PM
What temperature was the wort when you measured pre-boil volume?  For a long time I didn't realize what a difference this makes.  For example volume measures 5% higher at boiling than at room temperature. 

I always assume I'll have my burner going as soon as bottom of the boil vessel is covered with wort.  I know Beer Smith has a setting for "cooling lost percentage" under "Equipment."  I usually put this at 4-5% because I assume the wort will be quite hot when I measure volume (in the upper 100s/lower 200s).  I think this is 4% by default.

If you measured 7.5 gallons at high temperatures it would be less going into the fermentor in addition to how much you boiled off.  If measured near boiling it would actually be 7.125 gallons at room temperature. 

In your example, you still would have had to had a 20% boil off rate and measured your pre-boil at near boiling to get that kind of loss.
Tristan, I pulled all of my wort into the kettle before I put the flame to it. So, the wort was measured at mash temps, slightly cooler do to the time involved and the gradual cool down. 140's - 150's or so....
Title: Re: Came up short!!!!!!
Post by: morticaixavier on June 14, 2011, 06:02:41 PM
Seems like the boiloff amount is reasonable, if a little high but explainable by low humidity, surface area. The big question here is still the disapearing sugar. as tomsawyer pointed out, the post boil gravity should have been much higher. Unless there was ALOT more wort left in the hops/break material in the kettle post boil. if there was 1.25 gallons left at the bottom of the kettle instead of the stated .25 that would work out just about right. 430 points / 6 is 1.071

**EDIT** combine that with the volume increase/decrease caused by temp differncial and you get closer to that 1.5 gallons per hour number as well.
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 14, 2011, 10:43:13 PM
Man....This forum truly is awesome. You guys are all so resourceful and you need to know how much your insight is appreciated. I will be paying very close attention to my boil off moving forward and will ultimately shoot for more wort in the kettle pre boil so I can wind up with my desired 6 G to the fermenter.

Morticaixavier- As for the break material left in the kettle, I dumped it out into a measuring picture to make sure. It was 1 qt, exactly.

I have not calibrated my hydrometer yet. Didnt have any distilled water @ home last night. I'll test it tonight. I can see how the little slip of paper inside with the scale on it could slip down the inside tube of the hydrometer and effect accuracy. What a pain in the ass. I would have thought that tool was on point all the time, no questions. Been at this for a while now and still learn new stuff all the time. I'm pretty sure if I adjust my pre boil volume to compensate for my boil off and I dial my hydrometer in....I should be in business! Whats the word on refractometers? I've bought a few hydrometers over the last five years. I think if I have to spend any more money to measure sugar, I may as well make the jump to the refractometer and stop wasting time and money on the hydrometers. Are they more accurate? Durable? Thoughts?
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 14, 2011, 11:16:12 PM
A refractometer is a fine tool for measuring OG, its a pain in the a$$ to use for FG and not that accurate.  I have the refrac because I make wine and I do love it for the initial measurements.
Title: Re: Came up short!!!!!!
Post by: tubercle on June 14, 2011, 11:27:12 PM
 Don't invest in distilled water just yet. Tap water at room temperture will give you a good indication if you need to research further. If it is way off with tap water it will be way off with distilled water. If it real close. within a couple of 00,s, then you might want to get distilled water and test at the exact calibration temp.

  If it is off a good bit then trash it; they're cheap and not worth doing all the calculating.

 Tip of the day: If you just have one, you will break it soon. Buy 2 and it will last forever.
Title: Re: Came up short!!!!!!
Post by: Hokerer on June 15, 2011, 01:16:20 AM
Tip of the day: If you just have one, you will break it soon. Buy 2 and it will last forever.

+1  And applies to way more than just hydrometers
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 15, 2011, 01:44:08 AM
A refractometer is a fine tool for measuring OG, its a pain in the a$$ to use for FG and not that accurate.  I have the refrac because I make wine and I do love it for the initial measurements.
How so?
Title: Re: Came up short!!!!!!
Post by: Hokerer on June 15, 2011, 02:02:10 AM
A refractometer is a fine tool for measuring OG, its a pain in the a$$ to use for FG and not that accurate.  I have the refrac because I make wine and I do love it for the initial measurements.
How so?

What's he referring to is the fact that refractometers are not accurate in the presence of alcohol.  They're fine for pre-fermentation measurements but once there's alcohol present, they don't read accurately.  There are various spreadsheets available that'll help you with correction calculations but they vary in accuracy and using them is probably the "pain in the a$$" he's talking about.
Title: Re: Came up short!!!!!!
Post by: cheba420 on June 15, 2011, 03:58:56 AM

 Tip of the day: If you just have one, you will break it soon. Buy 2 and it will last forever.
Tubercle is wise.

I see new hydrometer(s) in my future! Calibrated mine tonight and its 6 points off! Not huge but I'd like to dial that in a little.
Title: Re: Came up short!!!!!!
Post by: Will's Swill on June 15, 2011, 04:32:35 AM
Tip of the day: If you just have one, you will break it soon. Buy 2 and it will last forever.

+1  And applies to way more than just hydrometers

+1  And I used to think this applied to thermometers as well, but my last brew day was a three thermometer day.  That is - three thermometers went in the trash: my Farberware knockoff of a Taylor that I recommended in a another thread - it was reading 40F too high, and two standard floaters that were broken in the process.  I have a Polder remote thermometer in route now, but at this rate I'll be up to the cost of a Thermopen in no time.  >:(
Title: Re: Came up short!!!!!!
Post by: tomsawyer on June 15, 2011, 01:16:40 PM
A refractometer is a fine tool for measuring OG, its a pain in the a$$ to use for FG and not that accurate.  I have the refrac because I make wine and I do love it for the initial measurements.
How so?

What's he referring to is the fact that refractometers are not accurate in the presence of alcohol.  They're fine for pre-fermentation measurements but once there's alcohol present, they don't read accurately.  There are various spreadsheets available that'll help you with correction calculations but they vary in accuracy and using them is probably the "pain in the a$$" he's talking about.
What he said.