Author Topic: Refractometers, to buy or not to buy?  (Read 2504 times)

Offline iamjoeyjo

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Refractometers, to buy or not to buy?
« on: May 17, 2014, 07:57:27 AM »
I hate these dinky hydrometers. I always seem to get one that is not at the 1.000 mark, the paper inside has slid down and they are so easily broken. I also find because of this they are wildly inaccurate.

Are refractometers any better or just as inaccurate?  I have asked around and they arr selling them for aquarium use but I hear they do not work for alcohol and sugar if they are calibrated for salt?  Can anyone elaborate?

Offline brewfun

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Re: Refractometers, to buy or not to buy?
« Reply #1 on: May 17, 2014, 08:40:21 AM »
Refractometers work by bending light through a prism. The thin film of wort on top of the prism changes the refractive properties and the user sees a line that indicates what the percentage of sugar is.

The sugar scale is based on pure sucrose, but there is effectively no difference in a reading with maltose. *Full disclosure: my opinion on this point is contradicted by a bunch of articles that say there's a difference, but don't agree on how much difference or that it matters by more than a tiny fraction of a percent. In other words, the error doesn't amount to even 1.003, until you're at gravity >1.120.

Refractometers need very little liquid, which means it cools quickly. This is especially helpful in getting ongoing gravity readings during mashing, sparging, pre boil and post boil.

Since sugar changes the refractive index, a lack of sugar will, too. Same with the presence of alcohol. So, refractometers are not typically used after fermentation has begun. I would recommend investing is a "finishing" hydrometer that has a scale of 0-8 Plato (1.000-1.032). They're a bit pricey (>$US20), but can be kept in a protective box or the hydrometer jar on a shelf.

BeerSmith has a refractometer tool that offers calibration plus correction for fermenting and finished beer. Also, Brad's article on the subject is here:
Beer Appreciation is the space between pints.