re: Homebrewing Thread: Volume II

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Why's that?

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A refrax measures the refractive index of the sample liquid. Sugar dissolved in the liquid changes the refractive index (relative to pure water). Pre-fermentation, you can assume that the only thing changing the refractive index is sugar. But because alcohol also changes it, you can't assume that after fermentation begins.

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So i'll still need to pull out my hydrometer?

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Like I said, you can do a correction for it if you know the OG. Most brewing software will do it for you but if you want, I can post an equation that you can plug into Excel that will correct it for you.