No Chill gravity loss question

[bobeer]

Hi All! I've had great luck with no chill brewing over the past couple of years but something happened to my most recent beer that I can't quite pin down what happened. Maybe you all can help!

Brew day went a usual. When it came time to cut the heat the gravity in my refractometer said 1.069. The next day when I put the wort into the fermentor it was at 1.060. I've never had any gravity change from leaving the kettle covered overnight to cool down. I calibrated the refractometer and I also checked the reading against a hydrometer. Both were the same gravity.

I've had the gravity increase by maybe a point or 2 due to the little trickle of steam that escapes under the kettle lid throughout the night. I've never lost gravity, esp 9 points, by no chill brewing. Any ideas?

 

[Qhrumphf]

Any signs of fermentation? Spontaneous ferment would definitely do it. That's also the approximate gravity drop i would expect given the time frame (now that's with a normal pitch of yeast at proper rate, I wouldn't expect spontaneous move that fast).

Is the refract calibrated properly?

Edit: either you ninja edited or I missed the calibration part...

Was it calibrated BOTH days? The hot reading may have been off.

 

[bobeer]

Any signs of fermentation? Spontaneous ferment would definitely do it. That's also the approximate gravity drop i would expect given the time frame (now that's with a normal pitch of yeast at proper rate, I wouldn't expect spontaneous move that fast).

Is the refract calibrated properly?

Edit: either you ninja edited or I missed the calibration part...

Was it calibrated BOTH days? The hot reading may have been off.

No signs of fermentation that I could see. I put the kettle lid on for good at around 185 degrees. The lid was on the whole time after flameout except to throw in the wp hops at the 185 mark.
9 points in 24 hours with spontaneous fermentation seems like a lot but then again I'm not really sure. Ha.

I calibrated the refractometer both times I used it- on brew day and then on pitching day.

It's happily fermenting now so I suppose all will turn out ok in the end. The hydrometer sample tasted fine as well so I might just have to be ok with never knowing who stole my 9 gravity points.

 

[day_trippr]

How thoroughly did you mix the wort before that last gravity check?
Is it possible it stratified leaving thinner wort on top/where you sampled it?

Cheers!

 

[ba-brewer]

I use a refractometer to check mash progression and for monitoring the mash run off. I notice as the temp gets up over about 180F the gravity increases by about 4 or 5 gravity points sometime more. If I cool the wort first and test it then it gets closer to expectation. I don't think ATC works well with high temp wort or it could also be higher evaporation at that temp, dont know. I normally cross check against a hydrometer for FG and SG.

 

[bobeer]

How thoroughly did you mix the wort before that last gravity check?
Is it possible it stratified leaving thinner wort on top/where you sampled it?

Cheers!

I thought this too, since the condensation would drip off the lid and gather on the top of the wort, so I took a few samples as the wort drained from the kettle to the fermentor. It read the same every time; even when I cross-checked with a hydrometer.

 

[bobeer]

I use a refractometer to check mash progression and for monitoring the mash run off. I notice as the temp gets up over about 180F the gravity increases by about 4 or 5 gravity points sometime more. If I cool the wort first and test it then it gets closer to expectation. I don't think ATC works well with high temp wort or it could also be higher evaporation at that temp, dont know. I normally cross check against a hydrometer for FG and SG.

I thought the same thing with the temp and refractometers, even though mine is supposed to adjust for temp, so I used to always cross-check with a hydrometer. After several batches of the SG's being the same I've since just trusted the refractometer. Maybe it's time to start cross-checking again or, better yet, maybe it's time to start using the IC again...

 

[IslandLizard]

The problem lies in some evaporation will occur between taking the sample and your reading. Putting a drop of boiling wort onto the prism will evaporate somewhat, inflating your gravity reading. Let your sample cool down a bit first. Then the last 40 degrees or so will be absorbed by the prism without (partial) evaporation.

 

[bobeer]

The problem lies in some evaporation will occur between taking the sample and your reading. Putting a drop of boiling wort onto the prism will evaporate somewhat, inflating your gravity reading. Let your sample cool down a bit first. Then the last 40 degrees or so will be absorbed by the prism without (partial) evaporation.

Makes sense. I'll play around with this idea next brew day. Thanks!

 

[IslandLizard]

Makes sense. I'll play around with this idea next brew day. Thanks!

I either scoop an ounce or so out of the kettle with a metal cup that's placed into a larger cup/container with cold or ice water. Once it has cooled down a bit, I transfer a drop of wort to the prism on the tip of a knife.

Or I use one of those plastic sample pipettes with the bulb on the end, and chill it (inverted) in a small container with ice/cold water for a minute or so. Smaller quantities chill faster, but if too small could give errors due to evaporation. A 1-3 ml sample is usually fine.