I calculate my alc. % using my starting and final gravity readings from my hydrometer.
How accurate is this? Is a refractometer worth it for this task? They’re a bit expensive.
I find them invaluable. They are great for taking readings during the boil to see if I’m going to hit my target. I actually haven’t used my hydrometer since I got it.
For checking fermenting wort, need to make an adjustment. Most ( if not all ) brewing software has a function for this or there’s a spreadsheet on morebeer.com that will do the calculation for you.
You can buy a refractometer on ebay for about $25-$30 I believe. That’s where I got mine. Calibrate it with distilled water and you’re ready to go.
I have one and use it primarily during the mash and the boil. They’re very quick, accurate and easy to use. I can sample boiling wort with a dropper and get consistent readings. I wouldn’t brew without it. It may be the most valuable tool in my brewery.
I guess I’m not familiar w/ all of their functions. What target is it you’re checking during the boil? IBU’s? You can’t adjust gravity at that point beyond boiling off, right?
What ‘adjustment’ needs to be done to the reading? Don’t you just put a sample on the refractometer & look through to read?
Perhaps I need to look into some brewing software. I keep a manual (MS Word) brewlog and formulate all my recipes by hand.
Right, but if you take a reading right as you start the boil, but before adding hops, you can adjust the boil length and guarantee you’ll hit your target OG exactly.
Basically, but there are some subtleties. Pre-fermentation, you need to divide by a “wort correction factor”. Refractometer Estimates of Final Gravity « SeanTerrill.com
I adressed more of how to use a refractometer in brewing in a BBR interview last year: http://media.libsyn.com/media/basicbrewing/bbr09-02-10refract.mp3
OK. Thanks for the info. I’ll have to start pricing.
I always check my boil before adding late addition hops to see if I’m going to be close on my numbers. Based on the first 30-60 minutes, I can just what the rest of my boil will be like. So if i have a 15 minute hop addition and my numbers gravity is still a little low, I’ll add some time to the boil to raise it up and then add my 15 minute hops based on the new boil time.
If I add an extra 15 minutes to the boil, the bittering hop additions aren’t going to be affected too much. But if I have to add extra time at the end of the boil, my 15 minutes hops now start to become 30-45 minutes hops.
I’m probably not explaining it too clearly…I’m at work, have about 10 things going through my head…and I’m STARVING!!! 1 hour to lunch.
I loved my refractometer when it worked. For some reason, it started deviating from my hydrometer so I stopped using it.
That seems odd. Perhaps it was defective?
What basic calculation do you use for your gravity readings? Years ago I learned this one:
Starting Gravity - Final Gravity X 129 = Alcohol %
For example:
SG: 1.062
FG: 1.010
Alc: 6.708%
Is that how you calculate it? What was your refractometer showing for something like this?
That seems odd. Perhaps it was defective?
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Well, it worked fine for a couple years.
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What basic calculation do you use for your gravity readings? Years ago I learned this one:
Starting Gravity - Final Gravity X 129 = Alcohol %
For example:
SG: 1.062
FG: 1.010
Alc: 6.708%
Is that how you calculate it? What was your refractometer showing for something like this?
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No, the refractometer doesn’t show anything like that. It’s just an alternative for taking a gravity reading, not calculating ABV. And once the beer has started fermenting, the alcohol in it skews the refractometer reading so you have to apply a correction factor.
Well, it worked fine for a couple years.
[/quote]
What basic calculation do you use for your gravity readings? Years ago I learned this one:
Starting Gravity - Final Gravity X 129 = Alcohol %
For example:
SG: 1.062
FG: 1.010
Alc: 6.708%
Is that how you calculate it? What was your refractometer showing for something like this?
[/quote]
No, the refractometer doesn’t show anything like that. It’s just an alternative for taking a gravity reading, not calculating ABV. And once the beer has started fermenting, the alcohol in it skews the refractometer reading so you have to apply a correction factor.
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Gotcha. I’ll guess I’ll learn all that when I pick one up and read about how to use it.
A great place to start are the links that Sean (a10t2 ) posted above. I use his refined algorithms for my conversion from brix to sg. I check against a hydrometer reading every 4th batch or so and its close enough that I rely on the refractometer for all my sg measurements. I can’t imagine brewing without it.
While this is true, in my experience none of the existing spreadsheets or conversion factors for post fermentation refractometer readings are very accurate. They are sometimes off by more than 4 points from what my hydrometer reads.
I use my refractometer pre-fermentation and stick to the hydrometer for post fermentation.
Which comes back to my original question. If I’m getting the info I need from my hydrometer, do I really need/is it really worth getting a refractometer? I have other things I could use the $$ for.
I love my refractometer and if it broke I would get another one. The small sample needed for testing and the ability to chill/test quickly makes it worthwhile for me. It’s a bit of a luxury and I don’t know what other things you want to spend the money on, you’ll have to prioritize 
+1
This is my practice as well.
Mine too.
Get the refractometer with ATC. Invaluable.
Does “conversion factors” plural mean you’ve tried mine out and it didn’t work for you? As far as I know every other tool uses the same formula.
If you’re calculating %alcohol in the finished beer, a hydrometer is the way to go. Yes, you can use a refractometer but there is a bit of math involved, whereas if you use a hydrometer, it’s the difference between the pre-fermentation gravity and the post-fermentation gravity.
If you want to take gravity readings through the mash and boil, then a refractometer is more practical.
OK. Thanks guys. I’ve got a decision to make…