Should I bother taking the OG FG?

People do pour the wort back in...if they've been studious in their sanitation.

That said, I would snag a refractometer...it's just easier. Be aware that you have to use an adjustment calculator when taking the FG...as they are not accurate in the presence of alcohol.

 

With an extract batch, you're gonna get real close to the OG if you follow directions, so that may be negligible...but taking an FG is important to know the final ABV and how the yeast performed. I think it's crucial, but if you just want to drink "beer" and don't care it's ABV or the amount of fermentation that took place, not measuring seems fine. Most folks brew 5+ gallon batches, so dropping a sterilized hydrometer into a fermentation bucket isn't a big deal for getting OG or FG, but in a glass carboy, you pretty much need that sample. As far as putting it back in...once again, if you don't have high standards or expectations, then the risk of contamination may not be a concern with you, so throw it back in. I like to finish/drink the test sample to get an idea of what flavors are developing or are currently in that brew. Homebrewing is all about personal decision and just because everyone else is super sterile doesn't mean you have to be, but don't expect high standards in your product if you don't have high standards in your technique.

 

Honestly, if you are using all extract and just steeping grains, OG is less important assuming the kit ranges are accurate and your water levels/boil off rate is average. FG is a little more useful if you are concerned that your yeast is finished. If you are considering getting either a refract or a hydrometer, get a refract. For a 1 gal kit, the tube will waste a larger percentage of your beer.

As far as returning wort sample during boil, do it all the time. Once the beer has started fermenting, it's just not worth the infection/oxygen introduction for me. With a refract, you are taking drops for FG.

 

It's well worth the bother to monitor and record the various gravities all along the way from the pre-boil to bottling. It's the only way to know for sure whether your process is proceeding as intended.

It's true for small batch brewers ...

... which is why we prefer to use refractometers instead of hydrometers.

The reason ...

.. is conventional wisdom is frequently wrong. I've had no regrets returning hydro-samples to the fermentor or bottling bucket.

 

"Some home brewers be,
Knowing something that's not so,
They're ok with that."
Humbletron Haiku

 

You don't necessarily need to check gravity, but you'll probably want to. With extract beers, your SG is more or less predetermined: if you add x amount of extract into y amount of water, you get a certain number of gravity points. (It becomes more important to check pre-boil gravity and SG when you're making all grain beers, because you'll want to track your mash efficiency.)

However, even with an extract beer, you will probably want to check final gravity, if for no other reason than that it's the best way to know if you beer if your beer has finished fermenting. After a while, you become confident that you can usually tell when a beer's done just by looking at it, but this isn't true in the beginning.

Most people don't pour their samples back into the fermenter, but then most brewers are doing 5 gallon batches where it doesn't seem like such a big deal to waste four ounces of beer. I personally would not return a sample to the fermenter: aside the possibility of infection (which can be minimized if your sanitation practices are really good) you will certainly oxidize your beer: there really isn't any way I can think of to take sample and return it to the fermenter without picking up a fair amount of oxygen. But do what ye will.

 

You should check the FG especially. Its the only way (besides waiting three weeks) to know for sure your beer is done fermenting.Don't believe the often given advise that no air lock activity means your beer is done or that all beers are done fermenting within a week.

 

My advise pertained only to getting this beer on the fermenter. Definitely get a refractometer soon so you can check OG and FG of every beer on. The data comes in very useful when tracking ingredient conversion or trying to identify problems after the fact.

 

Even if you are brewing extract recipes, I think it's important to get into the habit of taking an OG just so you'll be in the habit of doing it when you go to all-grain brewing. If you are doing extract brewing (or all grain) it's still very important to make sure that the amount of wort that you have after your boil (allowing for trub displacement) is pretty darn close to the amount of liquid for which your recipe is created.

 

As already stated, OG is not a big deal with extract brews. You can pretty much trust what it says on the label. Checking FG, on the other hand, is important for all the reasons cited, above.

Regarding returning the sample to the fermenter - I don't do it. It's just too risky, IMO, for the sake of a few ounces of beer (I know - that's the paranoia talking). I also find it informative to taste the wort at different stages of fermentation, so it serves that purpose.

FWIW, I prefer a refractometer over a hydrometer, mainly because it's easier, but also because, like you, I hate to 'waste' beer. The downside is that there's nothing to taste. Regarding the need to calculate the FG from the Brix reading - while that's true, you also should do that with a hydrometer, since alcohol affects the density of the wort as well as the refractive index. We just choose not to because the number we get from the hydrometer is close enough for our purposes, and the errors, such as they are, are built into the homebrewing lexicon (not sure if that's exactly the word I want to use, but it's early, so I'm going with it). The numbers are wrong, but we know what they mean, so we ignore it.

 

It's true that alcohol does affect the density (gravity) of the beer, as read by a hydrometer. But the ABV formulae don't ignore it. If they did, they'd give very much too high ABV answers. The simplest ABV formula (the one most use) corrects for this for one specific middle of the road case, but it's less accurate when you move away from that one case. The more complex ABV formulae are more accurate over a wider range of cases, and are pretty dang good. But my (long winded) point is that the formulae don't ignore the fact that alcohol affects gravity, and do (in effect) change the FG reading. It's just that the underlying process (e.g. X weight of sugar makes Y weight of alcohol, etc) has been reduced algebraically, so it's not obvious when looking at the final formula that the FG has been effectively changed.

It's actually pretty astonishing, when you get into fairly high gravities, how different the answers between the simple formula and the more complex formulae are.

 

That's exactly my point. We generally interpret the raw FG as a measure of residual sugar, even though it's not accurate. 1.010, for example means something very different if we started at 1.050 versus 1.090. The formulae we use virtually all tell us that the ABV of the bigger beer is twice that of the smaller beer - there's no adjustment that factors in the OG (a non-trivial factor). The 1.090 beer has more residual sugar, but we treat it like it's the same - and, indeed, it's close enough for our purposes. The numbers are wrong, but we just roll with them, because they give us a pretty reasonable idea of how much we can drink before we're two sh*ts to the wind

That said, the typical homebrewer does not have an arsenal of precision instruments at his/her disposal, so this is largely an academic discussion. The numbers tell us, with some confidence, when fermentation is done, approximately how our bodies will react to that beer, and a few other things.

 

This is where we disagree. I don't look at a gravity of 1.000 and think "no sugars left." Also, I include the ABV formulae as part of "we," and the formulae do not interpret the raw FG directly as a measure of residual sugar, because the formulae know there's a difference between apparent attenuation and actual attenuation, and know that the amount of sugar erroneously reported by the FG reading is not correct. There's an adjustment that's not obvious looking at the formulae because of algebraic reduction.

Yes, you could, stepwise, convert the FG to an adjusted FG (reflecting true(er) sugars remaining), and then compute the ABV from there, using a standalone sugar weight to alcohol weight + CO2 weight formula. But in the end you'd get the same answer, depending on what adjustment (level of sophistication) you're making to the FG/remaining sugar (comparable to the different ABV formulae). Either way, you're still estimating the remaining sugars.

If there were a better way to calculate an estimated ABV (by doing something differently or in a different order), we'd have it. It's not that we have chosen to ignore something and could do better.

ETA: When I talk about the estimate being as good as it gets, I'm referring to the most sophisticated versions, not the "single term" adjustment version, which although a lot of people use it, is not great.

 

We're actually on the same page, I think. For reasons I cited above, I believe that one of the more simplistic formulae (ABV=(OG-FG)*131) is good enough for our purposes. I haven't looked at too many others since I built a spreadsheet that accepts Brix and does all the calculations for me. No matter how sophisticated the formula, if it doesn't factor in OG, there is no way to accurately determine how much sugar is reflected in the FG (the difference between OG and FG doesn't count. There's likely a Mathematical term for how OG must be used, but it escapes me at the moment). The result will still only be accurate for one OG - and we don't even know which OG was used as a reference.

Nor do I. My comment was probably a bit too broad. I meant that we plug that number into the formula as if that is exactly what it means. (at 1.000 FG, the 'Potential ABV' scale that we see on many hydrometers would be dead on).