Measuring gravity in 1-gallon batch without sacrificing beer?

[TripleC223]

I brewed up a 1-gallon Citra pale ale about 1.5 weeks ago, and it's getting close to time to check the gravity. I have brewed 5-gallon batches in the past, so pulling a sample with a thief to check SG has not really been an issue.

However, now that I only have 1 gallon of this delicious brew, I'd like to preserve as much of it as possible. Is there another way to test gravity without pulling 5-8 oz. and putting it into the hydrometer test tube?

I've read that dropping the hydrometer directly into a glass carboy is a no-no (possible broken glass in fermentor, krausen crud on hydrometer, etc.). Anyone have any techniques?

Currently I only have a hydrometer, a thief and a plastic test tube.

 

[SlitheryDee]

You can sanitize everything and just return the sample to the carboy. That's risky, but not impossible. You could also purchase a refractometer and use an online converter to get a correct gravity reading. That only takes a few drops of beer to perform, so you shouldn't sweat losing it too badly.

 

[Silver_Is_Money]

A refractometer scaled in Brix (Bx) plus this calculator (to correct its sugar density readings for the presence of alcohol instead of sugar) is your answer. Only needs 3 drops. Use 1.040 as your wort correction factor. Refractometers are going for about $24 on Amazon.

http://seanterrill.com/2012/01/06/refractometer-calculator/

 

[JayInAmes]

Is there a particular feature to look for with a refractometer? Lots of options out there. Seems like a handy purchase, though.

 

[Silver_Is_Money]

Multi-scaled (SG and Brix) should be given a pass. You want both scales to be Brix. The reason for this is that the SG scale is destined to be incorrect.

 

[jrgtr42]

Depending on how deep your carboy is, dropping it in may not be the worst. How much airspace and how deep the beer is.
I do that in my bucket fermenters all the time - though it is 5-gallon batches. Just sanitize the hydrometer well, lower it in and I give it a spin to throw off krausen and bubbles. I then leave it in there for the few days between checks. I've never had an infection yet (knock on wood.)

 

[DocScott]

Refractometer conversions aren't always the most accurate. I'd suggest just carefully placing the hydrometer in the carboy and taking the reading as long as it is deep enough.

I'd also be contrarian and say what's the purpose of the gravity reading? Yes, it will help you know the ABV more precisely. Yes, it will tell you if the beer is at terminal gravity if it remains stable over several days; but this will cost you 6oz (x2 or x3 samples). Assuming it has been a couple of weeks fermentation it is pretty safe to assume it is done, and the FG can be assumed to be at or near the attenuation profile for the yeast. Package it up, let it carb, put them in fridge to stall the potential for overcarb and enjoy the full gallon is my suggestion. (please, before I get yelled at for potentially creating bottle bombs, know that the only way to know if the beer is done fermenting is to check the gravity...)