Gravity Drop after cooling

[crashtest22]

Hey all,
I had a odd thing happen and wanted to see if anyone in here knew what was going on.
I brewed a stout that I made in BS
The calculated numbers
Pre Boil 1.064
Post Boil 1.081

My preboil was a little low at 1.062 but after 75 min boil the SG was reading 1.081 which is what it was supposed to be.
After 20 min whirlpool and about 45 min with the chiller the SG was 1.075

I can't for the life of me figure out why it dropped so much.
I was using a Refractometer btw

 

[FreddyMar3]

Hey all,
I had a odd thing happen and wanted to see if anyone in here knew what was going on.
I brewed a stout that I made in BS
The calculated numbers
Pre Boil 1.064
Post Boil 1.081

My preboil was a little low at 1.062 but after 75 min boil the SG was reading 1.081 which is what it was supposed to be.
After 20 min whirlpool and about 45 min with the chiller the SG was 1.075

I can't for the life of me figure out why it dropped so much.
I was using a Refractometer btw

What temps did you read at?

 

[crashtest22]

I read the first temp at around 180 deg and second at 75 or so

Usually after I take the first reading I let the refractometer sit for a min or two to cool

 

[Owly055]

I read the first temp at around 180 deg and second at 75 or so

Usually after I take the first reading I let the refractometer sit for a min or two to cool

Refractometer readings should not vary wildly with temp due to the thermal mass / cooling effect. A drop of hot wort should cool very rapidly. I have tested wort right out of the mash tun, then let it sit on the refractometer for a few minutes, and detected no significant difference.

 

[WrQth]

Check the calibration of your refractometer with distilled water before each brew. I rinse the dropper between samples just because but if a tiny drop is still in there and mixes with the wort sample the reading is more diluted resulting in a lower SG, could something like this happened to you? Also could there have been some hop debris in the first sample which could through off the reading as well?

 

[crashtest22]

I Calibrate before each brew so that should not be an issue.
I agree with temp not being an issue and know they are not listed as temp dependent.

I rinse and dry the refrac between each sample

Could have been some hop debris.

I am not overly concerned with the drop just curious as to why or what happened.
I didn't pull a hydrometer sample which I should have.
Either way its fermenting away at this time and I am sure it will be delicious

 

[crashtest22]

Just checked my refrac again and now its reading 1.002 with water.
I must have bumped it or something
But that would not explain why it went down. Should have gone up lol

 

[WrQth]

All-grain or extract? If extract, late additions? If yes, thoroughly mixed before sample taken?

 

[crashtest22]

It was a 11 gallon all grain....33.5 pounds of grains

 

[DrunkleJon]

another thought. is your refractometer an ATC (automatic temperature correction) model?

 

[acidrain]

another thought. is your refractometer an ATC (automatic temperature correction) model?

All refractometers are ATC since the drop of wort takes just a few seconds to cool.

 

[Onkel_Udo]

I really hope this is not the case but any chance your post boil volume grew just a tick from a leak in the chiller? Assuming we are talking a linear relationship, you would only need a 6% increase in volume for that amount of change.

 

[crashtest22]

yes ATC
I hope its not the chiller but that could be.
I will do a pressure test on it.

May be a non issue because I just figured out we added about 50 grams of Gypsum by accident
going to give her a taste test in a few more days to see if its even drinkable