Cry-drometer

[CraftBrewGal]

Okay... this hydrometer is driving me nuts. I just dont get it or something. The instructions that came with it are really vauge..
What i gathered---you fill the hyrometer testing tube and drop the hydrometer is--let it float--take the reading (OG)origonal gravity--- then take a reading at the end and subtract the OG to get your ABV??
How far off am i??
Also.... can you test your beer throughout fermention?
What do you normally do?

 

[Ski12568]

Sounds about right. I use a program called BeerSmith and it tells be my ABV after I get all my readings so I'm not sure about the math.

Yes, you can take reading while it is fermenting. That's a good way to know if you are done fermenting.

 

[LLBeanJ]

Well, not quite. You measure for OG and again for FG, then run the two through an equation to calculate %ABV. You can use the Brewer's Friend ABV calculator to do that.

And yes, you can monitor the gravity as it changes, but you're better off just waiting until the krausen drops + 3 days to take your first reading. Then take another reading 3 days later and if no change, go ahead and bottle, otherwise repeat until gravity is stable across two readings.

 

[Ski12568]

I also ale sure to get my wort sample SG, OG, FG to around 60F (what my hydrometer is calibrated to) so I get a good reading. For my FG I just use a hydrometer temperature correction calculator if it is above 60F to get the difference in readings.

 

[Qhrumphf]

Either take your sample at reference temperature (they tend to be calibrated to 15C/58F, 15.5C/60F, or 20C/68F, which one will either be printed on your hydrometer or on the paperwork that came with it) or correct the reading for temperature (use an online calculator, or there's usually a correction chart with your hydrometer). Read through the meniscus at the flat plane of the sample (the liquid will curve up a bit when it reaches the hydrometer, read through the curve, not at the top of it, unless your hydrometer explicitly says to do otherwise, very few hydrometers should be read at the top). And then the quick formula is (OG-FG)*131.25=ABV.

You're working with the specific gravity scale (usually marked 0.990 or so to 1.140 or so, with 10-20-30 and so on markings in between). If it's got scales for °Brix or °Plato you can use them with some different math if you want (Brix used more by winemakers and Plato used by pro brewers), but everything for homebrewers is based on specific gravity. Completely ignore the potential alcohol scale if it's on there, because that's for distillers and doesn't mean much to us.

 

[unionrdr]

As previously stated, the markings are 1000, then 10, 20, 30, 40, etc. The markings in between are read as 2, 4, 6, 8. I test mine after straining into the fermenter & top off is mixed in. It's at pitch temp at that point, so correction may not be needed. But here's a hydrometer correction tool anyway; http://www.brewheads.com/gravcorrect.php
I usually wait 10-14 days before taking a sample to see how far along it is. If it's within the FG range of the recipe, wait 3 days to take another. If they match, you can bottle it. Or wait another 3-7 days for it to clean up & settle out clear or slightly misty so as to get less trub in the bottles. My hydrometer says to read at the top of the meniscus, but some others you read straight through it as mentioned.

 

[paperairplane]

go to brewersfriend.com they have all kinds of calculators that will make it easy and no math

 

[beergolf]

ng. The instructions that came with it are really vauge..
What i gathered---you fill the hyrometer testing tube and drop the hydrometer is--let it float--take the reading (OG)origonal gravity--- then take a reading at the end and subtract the OG to get your ABV??
How far off am i??

The formula is (OG- FG) X 131= ABV.. Some use .131.25 but 131 is close enough.

 

[unionrdr]

I must've seen eight different formulas, but I use the Cooper's formula that is usually in range of BS2's. Cooper's is (OG-FG)/7.46 +.5=ABV%.

 

[Qhrumphf]

As far as ABV, the formula you use really doesn't matter all that much, since they're all approximations anyway. The only way to know the absolute ABV is to send out for lab analysis. Which you can certainly do, but there's not much point outside of curiosity unless you're a pro dealing with labeling laws.

 

[beergolf]

but there's not much point outside of curiosity unless you're a pro dealing with labeling laws.

True it is not perfectly accurate, but there is a point to knowing approximately the ABV. I want to have a good idea of the brew I am drinking. I don't want to drink a couple of 10% beers if I am driving. Or if I had a bad day at work I don't want a 4% beer. Sure a 1/4 or 1/2percent won't make a big difference but I want the ballpark.

 

[Qhrumphf]

True it is not perfectly accurate, but there is a point to knowing approximately the ABV. I want to have a good idea of the brew I am drinking. I don't want to drink a couple of 10% beers if I am driving. Or if I had a bad day at work I don't want a 4% beer. Sure a 1/4 or 1/2percent won't make a big difference but I want the ballpark.

Right, I completely agree. And all of the major formulas will get you close. Just no point in putting more stock into it than that, just understanding that it's "close enough" and nothing more.

Now I do believe in checking both OG and FG for brewing consistency purposes.

 

[ballsy]

Save yourself the time and chances of infecting with frequent SG checks. Just let it ferment for 3 weeks then check SG at time of dry hop and check again 5-7 days later to confirm no change then bottle. Few beers need more than this to finish (big beers like stouts, tripels, etc..). Use (OG-FG) * 131 to get ABV. I dry hop at 3 and keg/bottle at 4 unless I have a deadline (aka promised beer for an event) in which case I have done dry hop at 2 wk and keg/bottle at 3 week.