poppalarge
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I've seen some people measuring the gravity of their wort with some kind of microscope device.
What is such a thing called?
What is such a thing called?
That's the one.
How does it work?
Unibrow said:Mine was $40 on Amazon I think - works very well and helps because you only need a few drops of wort for the OG reading
gr8shandini said:A refractometer measures the sugar content of the wort by measuring how far light bends (or refracts) when as it passes through. You can only take direct measurements prior to fermentation, though. Once you have alcohol in the mix, you need to use a formula to correct the readings. Since you're unlikely to miss your OG when extract brewing, you're better off just using your hydrometer. However, they come in really handy when/if you go all-grain since you'll want to take multiple samples of hot wort, and the few drops you'll need will cool really quickly.
By the way, if you search ebay, you can find them for much less than $100. More like 30 bucks. Just make sure you get one with Automatic Temperature Correction (ATC) as they don't cost much more and it's one less calibration you have to keep track of.
Like this?
Refractometer ~$100
Its only $30
http://www.amazon.com/dp/B003H7ILCW/?tag=skimlinks_replacement-20
I just got mine and calibrated it with my last brew, put my correction @ around 1.0285 or something...for the next few brews ill definately keep using it and updating the calibration to see if my correction value changes much...but i doubt it.
Its only $30
http://www.amazon.com/dp/B003H7ILCW/?tag=skimlinks_replacement-20
I just got mine and calibrated it with my last brew, put my correction @ around 1.0285 or something...for the next few brews ill definately keep using it and updating the calibration to see if my correction value changes much...but i doubt it.
What calibration are you doing?
All I do is get distilled water (sg 1.000) and take a reading then adjust the screw under the black cap until the refractometer reads 1.000.
Hum...I did research 2-3 years ago saw the prices and said **** it. Now its that time of the year when the fat man comes. I now have a request. Thank you sir!!Its only $30
http://www.amazon.com/dp/B003H7ILCW/?tag=skimlinks_replacement-20
I just got mine and calibrated it with my last brew, put my correction @ around 1.0285 or something...for the next few brews ill definately keep using it and updating the calibration to see if my correction value changes much...but i doubt it.
What calibration are you doing?
All I do is get distilled water (sg 1.000) and take a reading then adjust the screw under the black cap until the refractometer reads 1.000.
Refractometer - Brix Correction Factor:
A Brix refractometer reading is based on the known values for percentage sucrose solutions. However, wort contains many substances other than sucrose, and many of them have different refractive indices than sucrose. For this reason, it is necessary to use a correction factor to convert from a Brix refractometer reading of raw wort to the actual gravity of the wort. The literature suggests this factor is between 1.02 and 1.06, with 1.04 often used as a default value.
To determine your own, brewery-specific Brix correction factor:
(1) Take a hydrometer sample of unfermented wort.
(2) Measure its gravity with the most accurate, calibrated hydrometer you have. Do not forget to do the temperature offset calculations. (Alternative: use a digital density meter or pycnometer -- the idea here is to get a very accurate measurement of the actual SG / Plato of the sample.)
(3) Convert this value to Plato if you measured in SG.
(4) Using a zeroed refractometer, take the refractometer reading of the same sample.
(5) Convert this value to Brix if measured in RI or Zeiss units.
(6) Brix correction factor = Refractometer reading (in Brix) / Measured Gravity (in Plato) E.g., Refractometer reading = 13.1 Brix Measured gravity = 12.7 Plato Brix Correction factor = 1.0315
(7) Do this with several different samples and average the results. The literature suggests that the value should be consistent within a particular brewhouse.
ajf,
I don't disagree with anything you say, but in the end, the inaccuracies you mention are "in the noise." For example, what's the accuracy of your hydrometer at anything other than 1.000? What's the accuracy of the thermometer you used to measure the temperature of the sample? How much error is there in your readings due to things like parallax, judging the meniscus, not having completely degassed the sample, etc.? I don't know the answer to any of these, but as a wild guess, I don't think anyone can expect to get better than within +/- 0.002 of the actual SG with a hydrometer. Similarly, a refractometer isn't all that easy to read and even though mine has lines for every 0.1 Bx, I can't really say I can read it better than the nearest 0.25 Bx. So that's a 0.001 error on top of whatever the accuracy of the refractometer is.
But the real question is, what kind of difference is noticeable to a taster? Since you're really only tasting FG, I would say that I can tell the difference between a beer that finishes at 1.005 from one that ends up at 1.015. But could I tell a 1.010 from either? I doubt it. So it looks like there's at least a 5 point spread in what I can discern in the finished product (YMMV, of course). I don't know what the magnitude of the errors you mentioned are, but I'm guessing they're much less than that.
Also, keep in mind that the yeast pretty much have the final say in how your beer turns out. Even with the best instruments and strictest process controls, the major brewers still have to blend batches to get a consistent product. I like to do what I can to be scientific about my brewing, but it often helps to remember that most of the time we're measuring with a micrometer and cutting with an axe.
All I was saying is that the conversion form Brix to Specific Gravity depends on whether you are making wine or beer.
If you are making beer, using a dual scale refractometer, or a conversion table will generally result in an estimated S.G. value that is 3 - 4% higher than the true S.G. value.
I have two hydrometers; a triple scale one that reads about 3 points high that I can get readings accurate to within about 2 - 3 points if I use a magnifying glass, and a finishing hydrometer that gives a reading accurate to 1 point with my reading glasses.
I can read my refractometer to within 0.25 Brix (1 point) without any problems.
Using the refractometer tool in Promash, I can translate 19 Brix to a S.G. of 1.075. This was confirmed against the S.G. reading from a narrow range hydrometer which has since got broken.
If I use a lookup table or calculator, I get a predicted S.G. of 1.079.
I'd much rather use a tool that gives accurate results, than something that has been proven to be inaccurate.
-a.
Are you applying a known Brix correction factor that you have calibrated your refractometer against? That may be where your losing your accuracy if you are just using the standard 1.04 correction factor most tools assume instead of calculating your own for your hydrometer and refractometer setup.
All I was saying is that the conversion form Brix to Specific Gravity depends on whether you are making wine or beer.
If you are making beer, using a dual scale refractometer, or a conversion table will generally result in an estimated S.G. value that is 3 - 4% higher than the true S.G. value.
I have two hydrometers; a triple scale one that reads about 3 points high that I can get readings accurate to within about 2 - 3 points if I use a magnifying glass, and a finishing hydrometer that gives a reading accurate to 1 point with my reading glasses.
I can read my refractometer to within 0.25 Brix (1 point) without any problems.
Using the refractometer tool in Promash, I can translate 19 Brix to a S.G. of 1.075. This was confirmed against the S.G. reading from a narrow range hydrometer which has since got broken.
If I use a lookup table or calculator, I get a predicted S.G. of 1.079.
I'd much rather use a tool that gives accurate results, than something that has been proven to be inaccurate.
-a.
So with all this talk about having to calculate correction factors, etc. to get a "correct" SG, why don't we just use Brix/Plato and ignore the SG (just like actual breweries)?
Brix/Plato is not intuitive or mathematical. It's a quaint, legacy measurement that will go away some day.
Specific gravity is the standard method in chemistry to compare any liquid to the density of water.
That's odd seeing as the Brix/Plato scale was invented as a way to make SG intuitively meaningful to brewers - http://en.wikipedia.org/wiki/Brix
In short, if your wort is 12*P, it's 12% sugar by weight. That gives most people a lot better idea of what's going on than knowing that it's 1.048 times heavier than water.
Good point. I still like the units that makes mathematical sense.
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