Refractometer Help....?

I purchased a refractometer a few weeks back and am just trying to corolate it to my hydrometer. Unfortunately, I can't figure the darn thing out.

The OG on my English Bitter read just shy of 13 brix, or about 1.052, with the refractometer, which I considered to be reasonably close to my hydrometer reading of 1.050.

However, the OG reading of my Imperial Stout was way different. OG of 1.086 with the hydrometer, and about 10 brix, or 1.040 with the refractometer. This considering a target of 1.090.

When I racked the Imperial to secondary a few minutes ago, the reading was 1.018 with the hydrometer, but still 10 brix, or 1.040 with the refractometer.

Clearly the refractometer isn't reading the Imperial correctly, but why?

Three things are going on:

1.) Refractometer readings are not accurate during and post-fermentation, because the ethanol changes the way light is refracted. There is software available that will correct for this discrepancy (e.g. Beersmith), although these conversions aren't 100% accurate - but you can get pretty close.

2.) Refractometers are very sensitive to air bubbles and solids (e.g. tiny hop particles) in the sample. Try to get as clean a sample as possible for your readings.

3.) To get the most accuracy for OG readings, you also need to correct the OG by what's called the wort correction factor. The fact that wort is not a pure sugar solution skews readings slightly. A common correction factor is 1.04. I have found that for my equipment/beers it's closer to 1.02. The MoreBeer spreadsheet assumes it's around 1.07.

I hope this helps!

ArcaneXor said:

3.) To get the most accuracy for OG readings, you also need to correct the OG by what's called the wort correction factor. The fact that wort is not a pure sugar solution skews readings slightly. A common correction factor is 1.04. I have found that for my equipment/beers it's closer to 1.02. The MoreBeer spreadsheet assumes it's around 1.07.

Click to expand...

So you're saying add .04 (or whatever your personal adjustment may be) to the brix calculation read as OG. i.e. after figuring out the brix to OG calculation I'm at 1.050. You're saying that my actual reading is 1.054, right?

I hope that made sense...

I think the wort correction factor is multiplied, not added, but I don't know the precise formula since I use software for those calculations. There are some online calculators that will do the trick though.

Here is an article that explains it all: Brew Your Own: The How-To Homebrew Beer Magazine - Projects and Equipment - Refractometers

GT