I just purchased this wine/beer thief so that I can take more regular samples over the course of fermentation. I plan to float my hydrometer directly in the tube of the thief, which requires me to draw off about an 8 oz sample. If I do this a few times a week over the course of fermentation, plus every day at the end to be sure FG has stabilized, this could add up to a lot of beer! So, I would like to return my samples to my carboy (maybe less a shot glass to taste).

If I were brewing in a bucket, I assume I would just press the tip of the thief against the side of the bucket just at the surface of the liquid. However, I don't think I can tilt the thief at enough of an angle through the neck of the carboy to hit the side. I don't want to release the sample straight into the neck of the carboy either, because that would allow it to splash and risk oxygenation. I suppose I could siphon from the thief back to the carboy... but that seems like a lot of trouble.

Does anyone else who brews in a carboy and uses this thief know of any simple tricks that I'm missing here?

And as a side note, I realize that I increase my risk of infection by returning samples, so I of course will be carefully sanitizing everything.

Edit for clarification: this particular thief has a one-way valve at the tip, allowing liquid to flow into the tube when it is submerged and stay in when it is withdrawn. As far as I can tell, the only way to release liquid from the thief is to press the tip against something, which "unlocks" the valve.

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    You know, taking so many samples is quite excessive. Since you can see into a carboy, you can watch the the foam rise and fall, and the yeast drop out. There isn't really anything you need to do while fermentation is happening. Furthermore, when the fermentation is done, you SHOULD taste the sample. I know several beginners that went to the effort of bottling beer, and then found out it was contaminated. – Pepi Apr 3 '15 at 3:27
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    But if you really have to have the data, there is another way. – Pepi Apr 3 '15 at 3:38
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    Leaving the hydrometer in the carboy doesn't work well if the krausen leaves an opaque stain on the walls, which I find it almost always does. And, that beerbug is cool, but if I can get the data I need out of my $20 thief plus hydrometer system, I'd rather not drop $250 on one of those... – Joe Apr 3 '15 at 17:41
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    what is the logic of taking frequent samples? If there is foam on the beer it is fermenting. While it's fermenting there is no diagnosis to be made, no action to take. When foam is gone and bubbles stop, then you can find out whether there is a problem. – Pepi Apr 4 '15 at 12:44
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    I agree with @pepi, limit regular sampling until after losing the visual cues of active fermentation, unless there's an indication something is wrong. You won't be able to change much, and the most frequent solution would be to just wait longer, anyway. I go by Charlie Bamforth's advice: "if you are not prepared to respond to a measurement, don't perform it. Unless a piece of data is required and useful there is no value in generating it." – Franklin P Combs Apr 4 '15 at 14:29

I like the taste of sweet wort, so I just drink my thief contents, but if you really don't want to waste your future beer, set up a one gallon sanitized carboy with its own airlock and put it next to your larger carboy. Keep your testing leftovers in this second bottle so that if contamination does occur, it won't ruin the whole batch.

If you are using a fridge as a fermenting chamber and therefore don't have room for a regular gallon-size jug, there are some tall thin drinking water bottles that are only about 3 inches in diameter. Might need to customize the stopper a little to make it fit the water bottle opening.

To minimize the likeliness of oxygenation when adding thief contents to a fermenting brew, you can always flood the air-space of the bottle with carbon dioxide before making the transfer. (assuming you have some bottled gas around).

  • This isn't a bad idea- it would certainly further reduce contamination and oxidation risk, so I might adopt something along these lines. However, I'd also like to figure out if it's possible to return stolen wort to the main carboy, which would be a lot simpler, if somewhat riskier... – Joe Apr 2 '15 at 19:56

tl;dr: If the thief is properly sanitized there's little reason that the sample can't be safely returned to the fermenter.

Longer answer: There's not really any reason to be checking the gravity until all visible fermentation has stopped (i.e. the kraeusen has dropped and the airlock isn't making any more noise). Generally, the idea is to wait for a few days (2-3 at least) after visible fermentation has ceased, and then start checking the gravity. When the gravity is the same for 3 days in a row, the beer is ready to bottle/keg.

I don't worry about emptying the thief against the neck of the carboy. If possible, I'd tip the carboy a bit so that the beer doesn't have as much of a chance to oxygenate on the way back into the carboy, but since most of the airspace inside the carboy will be filled with CO2 I'm not that concerned about it.

  • Tilting the carboy isn't a bad thought, depending on how full it is. I'd still like a way just to deposit it right inside, but this might be the best option... – Joe Apr 9 '15 at 18:07

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