Low OG after boil...

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Aloha_Brew

Well-Known Member
Joined
Aug 29, 2010
Messages
90
Reaction score
0
Location
Mililani
Okay, so this is my third all-grain batch i just completed up to fermentation. All three were done very much the same. Boiled water beforehand or filtered it before letting it cool to a temp around 150 for the mash with grain in the bed. This recent batch I kept around 152.

Here's the grain bill:
7 lbs Pilsener
4.5 lbs 2-row
2 lbs Munich
1 lbs Wheat
.5 lbs Peated
.25 lbs Carafa III

I used a little less than 9 gallons total for mash and sparge, adding some extra water during the 90 minute mash to keep temps up. My total yield was about 7 gallons.

After boil I yielded about 5.5-6 gallons. Oh, I also added 1oz Northern Brewer at 90 min, and again at 30 min, with 2oz Fuggles at 5 min. And Irish Moss and nutrients were added also at 5 min.

With my 2 previous batches I met expected OG; one being as high as .08. However, this time my OG was expected at .079 but was actually .05. Now, these homebrew calculators are alot smarter than me and the only way I can make myself get .05 after boil is if my yield was 8 gallons...which my 7.5 gallon pot just can't do with more than that even before boil.

Any ideas why my OG is so low? I can only figure I should have measured OG before boil to make sure I got enough concentrated yield from the mash. Otherwise, the only other possibility is I didn't boil long enough. But why just this batch???
 
You don't mention anything about your mash or sparge setup, and these factors are probably more important to this question than your particular grain bill. Also, 2 gallons is a fair bit of loss during mashing...is that standard for you?

All that said, my gut instinct is to check your grain crush. Consistent across all three batches
 
I got a standard cooler that can hold about 10-12 gallons. I have a small analog thermometer I place in the middle of the mash. To maintain temps for 90 minutes I usually end up adding 1-1 1/2 gallons. My method of adding water is the same for sparging: I get my 4 cup Pyrex cup, dip it in the pot I got at about 175-190, and just pour evenly on the top of the bed. I stir the mash after doing this and tend to stir every 10 minutes during the mash otherwise. From what I understand it's a fairly basic setup and practice.
 
Aloha_Brew said:
I got a standard cooler that can hold about 10-12 gallons. I have a small analog thermometer I place in the middle of the mash. To maintain temps for 90 minutes I usually end up adding 1-1 1/2 gallons. My method of adding water is the same for sparging: I get my 4 cup Pyrex cup, dip it in the pot I got at about 175-190, and just pour evenly on the top of the bed. I stir the mash after doing this and tend to stir every 10 minutes during the mash otherwise. From what I understand it's a fairly basic setup and practice.

Hmm...the mash and sparge seem alright. How did the grain crush look? Did you crush it yourself, or order it crushed?
 
Aloha_Brew said:
Crushed it myself at the brew shop, like I did with all my brews.

Hmm...can't say then. Something was off. If your crush and sparge were just like your last two batches, it must have been something else...temperature, grain weights, a hydrometer reading...

Next time, try taking a hydro reading at various points throughout to see if you can figure out where you're losing/not getting your initial points.
 
Yeah, I'm going to have to. The only big difference between my other two batches is this one was at a higher temp by 3 degrees and I also managed to maintain a constant temp better. The other two fluctuated kind of low. But this is also the first time I used so much Pilsen as the base malt...

Ah well, I'll chalk it up as a partial failure and look forward to the flavor at less "potency" as it were. Thanks for your assistance.
 
1. Crush (do you use a spark plug gapper or some other device to make sure rollers are the right distance apart?)

2. Temperature - 149 would give you more complete conversion than 152, so this could be part of the issue

3. Volume of water (can't tell what volume you used during mash, but too much could be a problem...but you have had success previously using the same volumes, so probably not a factor.)

4. Hydrometer - any chance that this instrument is miscalibrated?
 
I'll bet dollars to donuts that you are not getting full conversion in the mash. You need to get Iodaphor and do a conversion test, before you can be sure that your mash is done. My mashes always take 60-90 min before they turn up iodine negative. Then you need to maximize the lautering process. Whether batch sparging or fly sparging, you need to have enough water so that you don't leave a lot of sugar in the spent grain.
 
I got a standard cooler that can hold about 10-12 gallons. I have a small analog thermometer I place in the middle of the mash. To maintain temps for 90 minutes I usually end up adding 1-1 1/2 gallons. My method of adding water is the same for sparging: I get my 4 cup Pyrex cup, dip it in the pot I got at about 175-190, and just pour evenly on the top of the bed. I stir the mash after doing this and tend to stir every 10 minutes during the mash otherwise. From what I understand it's a fairly basic setup and practice.

I'm not sure I understand. You have to add 1.5 GALLONS of water to your mash to maintain the temperature? That doesn't make sense.

Here's what I'd suggest. Preheat your cooler, using 1.5 quarts of water per pound of grain, by adding 180 degree strike water to your cooler. Cover it. When it gets down to 165, then add your grain. Stir well, to equalize the temperatures throughout. If the temperature is different in one place than another, stir some more. When you're at your desired mash temp
(153 in my example), cover it and walk away for 60 minutes. Don't add 1.5 gallons of water during the mash! Get it right when you dough in, and don't mess with the mash.

And no more "about 175-190 degrees"! Be precise. Get a better thermometer, and use the correct temperatures for the mash and the sparge. Use the correct amount of water also. This will give you predictable and repeatable results, rather than "about this temperature" which you're finding doesn't really work.
 
1. Crush (do you use a spark plug gapper or some other device to make sure rollers are the right distance apart?)

2. Temperature - 149 would give you more complete conversion than 152, so this could be part of the issue

3. Volume of water (can't tell what volume you used during mash, but too much could be a problem...but you have had success previously using the same volumes, so probably not a factor.)

4. Hydrometer - any chance that this instrument is miscalibrated?

I don't do the calibration on the grinder, as they belong to the shop.

As far as the temperature goes I expected less conversion at 152, to try and make more unfermentables for body, but I didn't expect a loss of conversion by almost 40% with a difference of only 3 degrees compared to my other two all-grain batches.

I initially used about 3.5 gallons to start the mash but added about 1.5 gallons during the 90 minutes to maintain temps. I then sparged with about 3.5 - 4 gallons. The overall amount wasn't based on what I have used previously but by the calculators I use.

The hydrometer is a glass tube so...no calibration needed. But I did verify that plain water read 1.00 after my reading. Plus, I thought the body of the hops and grain mash might have been interfering so I retested after letting the wort settle for a bit...taking only the clear liquid without much of any materials, but no win.
 
I'll bet dollars to donuts that you are not getting full conversion in the mash. You need to get Iodaphor and do a conversion test, before you can be sure that your mash is done. My mashes always take 60-90 min before they turn up iodine negative. Then you need to maximize the lautering process. Whether batch sparging or fly sparging, you need to have enough water so that you don't leave a lot of sugar in the spent grain.

It is possible that there was more sugar left after I finished my sparging but I wasn't going to boil past the level I had figured for a 5 gallon batch within my pot, calculating for boil off (which I still managed to exceed by about a gallon and a half or so with a 90 minute boil). I let the mash sit for 90 minutes before taking the time to sparge so I know for sure that full conversion should have been completed. Additionally, my methods are exactly the same this time as it was with my other batch with a 1.08 OG. So, I'm not sure why everything would change so much between one instance and another...
 
I'm not sure I understand. You have to add 1.5 GALLONS of water to your mash to maintain the temperature? That doesn't make sense.

Here's what I'd suggest. Preheat your cooler, using 1.5 quarts of water per pound of grain, by adding 180 degree strike water to your cooler. Cover it. When it gets down to 165, then add your grain. Stir well, to equalize the temperatures throughout. If the temperature is different in one place than another, stir some more. When you're at your desired mash temp
(153 in my example), cover it and walk away for 60 minutes. Don't add 1.5 gallons of water during the mash! Get it right when you dough in, and don't mess with the mash.

And no more "about 175-190 degrees"! Be precise. Get a better thermometer, and use the correct temperatures for the mash and the sparge. Use the correct amount of water also. This will give you predictable and repeatable results, rather than "about this temperature" which you're finding doesn't really work.

Ummm...I'm not sure where you're surmising all this "what I need to do" is what I didn't do...but I assure you that I did preheat. I put near boiling water in in fact, and left it to cool down to about 165, then added my grain to get a temp right at my desired spec of 152. The only reason I added water later was because I check my mash...which means that I was able to observe a drop in temperature of several degrees within about 30 minutes.

The 175-190 temperature range is due to my heating up reserve water after the mash was already started. I initially added .5 gallons at about 30 minute intervals...the first at about 170-175, the second and third at about 190.

No need to call me stupid without saying the word itself... I may be relatively new to this but I have some knowledge, so please don;t assume I'm an idiot without getting to know me better first. :ban: Cheers!:mug:
 
Aloha_Brew said:
Ummm...I'm not sure where you're surmising all this "what I need to do" is what I didn't do...but I assure you that I did preheat. I put near boiling water in in fact, and left it to cool down to about 165, then added my grain to get a temp right at my desired spec of 152. The only reason I added water later was because I check my mash...which means that I was able to observe a drop in temperature of several degrees within about 30 minutes.

The 175-190 temperature range is due to my heating up reserve water after the mash was already started. I initially added .5 gallons at about 30 minute intervals...the first at about 170-175, the second and third at about 190.

No need to call me stupid without saying the word itself... I may be relatively new to this but I have some knowledge, so please don;t assume I'm an idiot without getting to know me better first. :ban: Cheers!:mug:

Now, now, settle down... Nobody has said anything about you being stupid but you :D

Glad to hear your method is in control of temps, but based on your post I had exactly the same concerns as Yooper. Perhaps she and I misread in the same way, but when somebody with three brews under their belt starts talking about 15 degree swings and 35% efficiency, it's not unreasonable to make some suggestions, eh? I (now understand that the big range referred to only your temp raising water, but that wasn't clear to me).

That said...

There's no way 1.5 gallons of 175-190 water would have been required to nudge a mash up by 3 degrees. That would be violating thermodynamics. Something is incorrect. Either a temperature, or a volume, or something else.
 
No harm done...except to my gravity. :p

I would agree with you about the temperature, because it doesn't make much sense to me either. But based on my numbers my previous two brews were at 75-77% efficiency with lower temps. I had trouble with maintaining temps at 149 for one and 151 for the other. So, the temps were actually lower than that for a longer period.

The analog thermometer was also reading about 8 degrees off I noticed during my recent brew; when I checked my temp after about 30 minutes there was a big difference. With the thermometer in the corner it read 152 when I first mixed the grain. After the 30 minutes it read 142 so I added .5 gallons but it didn't change even after mixing. I checked on a whim, moving the thermometer to the center and it read 152 again. I know there are inaccuracies with it but it did get me good results with it in the corner for the previous 2 batches.

I am still tweaking my setup but I was wondering if others had the same problem with a similar grain bill...as this is the biggest difference between this and my last two brews. I just can't comprehend that a temp difference of 3 degrees or so would make an equally "big" difference...but the constant higher temp could have ended up being the crutch to this brew after all. That was my point in posting my troubles...to get some feedback from those who experienced similar problems and found or just understand a solution.

Again, no offense taken and hopefully nobody offended!
 
The analog thermometer was also reading about 8 degrees off I noticed during my recent brew; when I checked my temp after about 30 minutes there was a big difference. With the thermometer in the corner it read 152 when I first mixed the grain. After the 30 minutes it read 142 so I added .5 gallons but it didn't change even after mixing. I checked on a whim, moving the thermometer to the center and it read 152 again. I know there are inaccuracies with it but it did get me good results with it in the corner for the previous 2 batches.

There's the rub. Your temperatures are bouncing all over the map. I don't think something went wrong on your third brew; I think you got lucky on your first two. Temperatures need to be relatively precise. Three degrees will mean only the difference between a fuller beer and a drier beer, but 10 degrees will mean the difference between beer and not-beer. You are ending up with pockets of hot and cold wort, and that is making your temperature readings almost useless. The broken thermometer doesn't help.

My guess is that your average mash temp was well, well above what you thought it was for the bulk of its time. This nuked the enzymes, and left you with poor extraction. You've got a mash cooler. That's great. It's one of the easiest ways to mash. But, you've really got to follow all of the warnings that tell you to LEAVE IT ALONE :D

Use one of the calculators to figure out your strike water temp, preheat your cooler, get your strike water up to temperature as per a high quality thermometer, dump it in with your grain and stir like crazy for five minutes. Until your arm hurts. After that, put the lid back on and walk away. Don't check it, don't stir it, don't do anything. Far, far better to be off by a couple of degrees for the whole mash than to be off by double digits of degrees for parts of it.
 
I've been hosed by a bad thermometer before, take this advice. Get yourself 2 of them, (I use 1 instant read digital, and 1 analog) and check them against each other each time before you brew. Make sure they are both reading the same, It would be highly unlikely that they would both become off, the same direction @ the same time. When you first get them, check them each in an ice water slurry, and boiling water. Lastly, if you use one of those cheap digital meat thermometers with the braided cable going to the probe, don't get that cable wet, the liquid will run down the line, and into the poorly sealed probe and throw your readings WAY OFF, even as much as 20 degrees.
 
Ummm...I'm not sure where you're surmising all this "what I need to do" is what I didn't do...but I assure you that I did preheat. I put near boiling water in in fact, and left it to cool down to about 165, then added my grain to get a temp right at my desired spec of 152. The only reason I added water later was because I check my mash...which means that I was able to observe a drop in temperature of several degrees within about 30 minutes.

The 175-190 temperature range is due to my heating up reserve water after the mash was already started. I initially added .5 gallons at about 30 minute intervals...the first at about 170-175, the second and third at about 190.

No need to call me stupid without saying the word itself... I may be relatively new to this but I have some knowledge, so please don;t assume I'm an idiot without getting to know me better first. :ban: Cheers!:mug:

I didn't call you stupid or infer that I thought that. I was just saying that it's not possible for a preheated cooler to lose that much heat. Some of the outdoors brewers probably lose some heat, but unless you're mashing in the artic tundra, you won't lose 10 degrees in an hour. I lose about 1 degree if that. One thought is the size of the grainbed, too. What I mean by that is if you have a very big mashtun and a small grainbed, that could be a factor.

A precise thermometer is a necessity, that was the other point I was trying to make.

Sorry to make you feel like I was namecalling. I was actually trying to be helpful. I guess sometimes the internet forums make things difficult to "translate" well. I don't know what I said or did to make you feel I was insulting you. There are lots of helpful people here who you may "get along" with better than with me.
 
Use one of the calculators to figure out your strike water temp, preheat your cooler, get your strike water up to temperature as per a high quality thermometer, dump it in with your grain and stir like crazy for five minutes. Until your arm hurts. After that, put the lid back on and walk away. Don't check it, don't stir it, don't do anything. Far, far better to be off by a couple of degrees for the whole mash than to be off by double digits of degrees for parts of it.

Lots of good advice on here so far but I think the above hit it right on. I just finished my first all grain batch last weekend. Being paranoid prior to the brewday I did some tests. The first of which included adding my strike water to my cooler mash tun and checking temps every ten minutes...I noticed that I lost almost 10 degrees just by opening the lid of the MT every 10 minutes.

My second test, I added the strike water and let it sit for the hour. I lost 2 degrees.

To the OP...the first thing that struck me was that you were stirring the wort every 10 minutes. Big no no...once you hit your temp. Close the lid and let her sit. Check your temp at the end and take note. You can adjust that later.

One last thing I noticed about my analog thermometer is that it takes a good 3-5 mintues for it to get a level reading. I will be getting a quick read digital thermometer before my next batch.
 
I didn't call you stupid or infer that I thought that. I was just saying that it's not possible for a preheated cooler to lose that much heat. Some of the outdoors brewers probably lose some heat, but unless you're mashing in the artic tundra, you won't lose 10 degrees in an hour. I lose about 1 degree if that. One thought is the size of the grainbed, too. What I mean by that is if you have a very big mashtun and a small grainbed, that could be a factor.

A precise thermometer is a necessity, that was the other point I was trying to make.

Sorry to make you feel like I was namecalling. I was actually trying to be helpful. I guess sometimes the internet forums make things difficult to "translate" well. I don't know what I said or did to make you feel I was insulting you. There are lots of helpful people here who you may "get along" with better than with me.

Nah, no problem. I get a little too touchy about my beer sometimes. I'm going to invest in a good digital thermometer as I believe that the temperature differences I had could have been largely due to the large amount of grain I had.
 
Back
Top