How can I calibrate my refractometer?

Several months ago, I bought refractometer and followed the instructions to calibrate it. I've even google'd about refractometers and they all said to calibrate it with drops of distilled water, then adjust the screw on top with a screwdriver, until the line is level with the zero.

Long story short, according to the refractometer, all of my beers have finished fermenting at 1.030+ with OG's of around 1.060. Tonight I finally grabbed my hydrometer and dropped it in the carboy to get a gravity reading and the hydrometer reads 1.014!

So is my hydrometer correct or is my refractometer? And if my refractometer is off, how can I calibrate it?

Additional info that may or may not be important: After I saw that my refractometer was reading differently from my hydrometer, I adjusted the refractometer, so that it was reading the beer the same as my hydrometer. Then I dropped some distilled water to see if it was at zero and the refractometer level read off the scale (e.g. the entire screen was blue).

So is there anyway to fix my refractometer? Or is the hydrometer off?

Alcohol distorts refractometer readings, so after fermentaion has started you need to make some calculations to compensate. Even after making the adjustments, refractometer readings aren't very accurate in the presence of alcohol, often being off by several points. You should rely more on your hydrometer for FG readings. Here's a spreadsheet that calculates the adjustments for you.

IMHO refractometers are pretty worthless after fermentation has started, but YMMV.

+1 on refractometer less then effective after fermentation begins

But that said, to calibrate a refractometer the common advice is to use distilled water. You just need a few drops to cover the measurement window so bring a cup of water to a boil in a sauce pan and then cover the pan with a clean cool lid, remove from the heat and count to 10. You will have all the distilled water you will need in the underside of the pan lid. Place a few drops on the measurement window, and use the adjustment screw to zero out the refractometer.

Tap water should read the same as distilled water, unless you've got some really funky tap water for some reason, but that would be extremely rare. The resolution on the cheap Chinese refractometers that most of us use is not all that hot to begin with.

1. you do need to have recently calibrated with 'clean' water of the same temp as the sample.
2. is the OG off too or just final gravity? as stated, alcohol skews it and you have to do additional math.

I only use it to get an OG. I hydro everything else. I've used tap water to calibrate a few times, unless you have crazy well water it shouldn't be off by more than a few .001 points.

Thanks guys! I didn't realize that the alcohol throws off the reading on the refractometer.

i zeroed to my tap water, as that is the brewing water source.

malkore said:

1. you do need to have recently calibrated with 'clean' water of the same temp as the sample.
2. is the OG off too or just final gravity? as stated, alcohol skews it and you have to do additional math.

I only use it to get an OG. I hydro everything else. I've used tap water to calibrate a few times, unless you have crazy well water it shouldn't be off by more than a few .001 points.

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What kind of math are we talking about? I don't have excel on my computer, so the morebeer program is not gona work for me.

use refractometer for SG and hydrometer for FG...works for me

If you keep track of a reading with a hydrometer during fermentation and write down the coinciding reading from your refractometer, could you not over time come up with a correction card?

you can get openoffice for free and use the morebeer xls sheet. That or Beesmith is good. The morebeer sheet allows you to use the refractometer through the whole fermentation as long as you enter the SG in correctly.

goose1873 said:

use refractometer for SG and hydrometer for FG...works for me

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Just remember that the alcohol influences the hydrometer, too.

I use the hydrometer whenever I have the time to desinfect all the equipment needed to use my winethief, measure SG and return it into the fermenter without infecting it. When I just want to see if fermentation is done, I use a new, desinfected plastic straw to extract a few drops, and mesure with the refractometer.

Vinocalc has some nice calculators for finding the Current Gravity and the residual sugars left with both hydrometer and refractometer(even with usig both).

Islandboy85 said:

If you keep track of a reading with a hydrometer during fermentation and write down the coinciding reading from your refractometer, could you not over time come up with a correction card?

Click to expand...

The formula for converting is crazy long and intense....you really need to find a spreadsheet calculator that's been mentioned.

JuanMoore said:

Alcohol distorts refractometer readings, so after fermentaion has started you need to make some calculations to compensate. Even after making the adjustments, refractometer readings aren't very accurate in the presence of alcohol, often being off by several points. You should rely more on your hydrometer for FG readings. Here's a spreadsheet that calculates the adjustments for you.

IMHO refractometers are pretty worthless after fermentation has started, but YMMV.

Click to expand...

As usual JuanMoore nailed it. I love my refractometer and use the correction chart in BeerSmith but I honestly only trust a hydrometer for the FG reading. I do use the refractometer up till the point gravity has leveled out because it waste less beer. But for FG I'm still stuck on a hydrometer. Also as was said YMMV.

What about throughout the brew day. I calibrate mine before each reading, I noticed as my brewery heats up from the boiling wort my refractometer gets out of calibration. Do any of you do this too?