First AG mess

[sbsmann]

Friends,

Did my first AG brew this weekend as a Northern Brewer AG kit (German Alt beer). Not sure where I went wrong but it definitely seems that I screwed up somewhere. The OG on this brew was suppose to be 1.052 and I recorded a ridiculously low 1.032. I took this reading of the full 6.37 gallons of wort pre-boil. How is that OG even possible after a sacch rest at 151 degrees (in 3.37 gallons) for an hour and several gallons of sparging at 170 degrees? I still can't figure out where I went wrong? After a good hour boil and cool down to 70 degrees my next reading showed 1.023. I am the newbie here so I'd like to hear thoughts on how I could get such wacky readings and produce a liquid with virtually no alcohol potential? Not sure why I even threw it into a carboy, but I did and the only good news is that I had a rather aggressive fermentation the following day that generated a ton of Krausen and needed the full blow-off tube. The fermentation made me feel a little more optimistic that there was plenty of sugar for the yeast to consume, but I still am not confident this will work out. Is there user error in reading a refractometer or any other ideas how I could have gotten such bad gravity readings? I just don't get it! HELP!

 

[d3track]

Did you stir the wort in the kettle both times before taking the sample? It can stratify in the vessel.

Unless you added top up water, there is a measurement error as pre-boil should always be lower than post boil and evaporation causes a density increase in wort sugars.

 

[jwelch1103]

d3teack is right, something's not copacetic here, gravity goes up after an hour of boiling not down. You made some other mistake.
Another thing, I've never made a beer with that low of an OG, but I do make starters (when I'm trying to grow yeast) in the 1.020-25 range and one thing I've noticed when these weak worts ferment I generally have a weak Krausen too. Not exactly a scientific observation but it appears you've had a very strong Krausen.
I think your OG was higher than you think.

 

[Sbe2]

Did you stir the wort in the kettle both times before taking the sample? It can stratify in the vessel.

Unless you added top up water, there is a measurement error as pre-boil should always be lower than post boil and evaporation causes a density increase in wort sugars.

I have had this happen, thought I hit my numbers after mashing. After an hour of boiling, and losing a gallon, my reading was the same. Now I stir after mashing before I take a reading

 

[beernutz]

You have to let the device itself and the liquid you're testing with the refractometer all move to ambient temp to get an accurate reading which can take several seconds. As others have said you also need to make sure to test a representative sample.

Do you have a hydrometer?

 

[sbsmann]

I wish I had a hydrometer to take a comparison test, but I did not. I shouldn't even have mentioned the final gravity reading because I had forgotten to take a reading until after the wort cool down. Then after about an hour after I pitched the yeast in the carboy I realized I forget to take a gravity reading so I took one out of the carboy realizing it probably won't be accurate. So really the focus here should be on my pre-boil reading which I feel was taken at the proper time after stirring and at room temp. My refractometer is new and it was my first time using it, so user error is possible. I just took a few drops and read it while thinking that low of a value almost seems impossible even if I did mess something up along the way.

 

[owmatooth]

looks like a good beer to me. I've never switched to a refractometer, still using old floaty. My SG readings are just ball park estimates anyway, can't expect any precise accuracy with the gradation scale on the hydrometer and the multitude of variables that can bump it a few percent one way or the other.
RDWAHAHB

 

[hlmbrwng]

Then after about an hour after I pitched the yeast in the carboy I realized I forget to take a gravity reading so I took one out of the carboy realizing it probably won't be accurate.

I'm not sure what you mean here. You want to take gravity when wort is cooled to room temperature in all cases. I put a few drops on my refractometer and let it cool for about 10 minutes. Usually, the gravity goes up by a couple of points.

Did you calibrate your refractometer using distilled water? This is very important. I think mine was off a bit before I did that. I'm not sure how far off it could be to begin with, but I imagine significantly.

If you calibrate it now, see how far off it is from 1.000 and then add or subtract that to what you measured. I don't know if the behavior is linear, but at least it should give you a good idea of what your OG is, if that was the problem.

 

[hlmbrwng]

You could be inaccurate by a few points at different stages. 1) not accounting for pre-boil volume compared to final volume, 2) not calibrated refractometer, 3) not allowing wort to cool. Added up, it could be a lot of error.

 

[sbsmann]

I seem to be making this more confusing than needed. My gravity reading was taken before boil and the couple of drops probably got to room temp in about 15 seconds at such a small amount of liquid. I did calibrate the thing with distilled water last week, so that should be good as well. I'd like to think my eyes couldn't read the small numbers in the refractometer, but I am pretty sure I read 1.032.

 

[doug293cz]

Turns out it's much more difficult than you think it should be to get a homogeneous wort for pre-boil sampling if you sparge. A gentle stir isn't going to cut it. You need to stir aggressively. Another option is to take a sample about 5 minutes into the boil, and adjust for the amount of boil-off you get in 5 minutes. The wort is usually very stratified initially, after sparged wort is added to the initial runnings, but once the wort is homogenized, it will not spontaneously stratify.

Sampling hot wort with a refractometer is subject to fairly large errors due to evaporation of water from the small sample size while on the refract's window (SG will read higher than actual.) Best to let the sample cool in the sampling dropper prior to putting the sample on the refract.

Brew on

 

[RustyHorn]

I seem to be making this more confusing than needed. My gravity reading was taken before boil and the couple of drops probably got to room temp in about 15 seconds at such a small amount of liquid. I did calibrate the thing with distilled water last week, so that should be good as well. I'd like to think my eyes couldn't read the small numbers in the refractometer, but I am pretty sure I read 1.032.

Hang on... the 1.032 was a pre boil reading? That would mean your final gravity would be much higher as the boil boils off water and the wort becomes concentrated.

 

[doug293cz]

Hang on... the 1.032 was a pre boil reading? That would mean your final gravity would be much higher as the boil boils off water and the wort becomes concentrated.

Except that we don't know if the pre-boil reading was reliable. If the wort was stratified, and OP pulled the sample from a zone rich in first runnings wort, the reading would be too high. If that were the case, then the lower post-boil reading could be correct.

Brew on

 

[RustyHorn]

Except that we don't know if the pre-boil reading was reliable. If the wort was stratified, and OP pulled the sample from a zone rich in first runnings wort, the reading would be too high. If that were the case, then the lower post-boil reading could be correct.

Brew on

Ahh, sorry. I didn't realise there was a post boil reading! I should probably read it properly before commenting 😇

 

[sbsmann]

At this point I'm just curious how the preboil gravity could be so low? I would say to ignore the post boil gravity bc here because it was a bad sample after an hour of fermentation.

 

[doug293cz]

At this point I'm just curious how the preboil gravity could be so low? I would say to ignore the post boil gravity bc here because it was a bad sample after an hour of fermentation.

If the pre-boil gravity was in fact much lower than target (we don't know if it was a good measurement or not), then it's likely that you suffered from low conversion efficiency in the mash (lots of starch not converted to sugar.) The most common cause of low conversion efficiency is too coarse a grain crush, such that the grits do not all get gelatinized before the mash is over. Since gelatinization occurs from the surface of the grits towards the center, the larger the grits the longer it takes for them to gelatinize. You can measure the conversion efficiency during the mash using the method here. Your options are to:

• Mash longer to get more conversion
• Crush finer (get your own mill, or ask your supplier to double crush)

Other things that can cause low conversion efficiency are:

• Dough balls (dry lumps) in the mash that don't convert because you need water contact to gelatinize. More stirring at mash in can remedy this issue.
• Mash temps either way too high or too low. High mash temps can denature the amylase enzymes before conversion is complete. Low temps inhibit gelatinization, and enzyme activity is slower. Inaccurate thermometers are the usual cause of temp errors. You should insure that you use calibrated thermometers.

Brew on

 

[ericbw]

One thing is CERTAIN: your gravity after boiling was not lower than pre-boil. It would be higher because you lost water. Same amount of sugar but less water.

I suspect a combination of temperature and maybe stratification. Maybe mis reading.