Measuring SG on small (3.5l / 1g) batches

I do small batch brewing (3.5l-4l) and using hydrometer is a big pain for them, as I need to take very big amount of beer out to test it. I've learned to do OG readings with refractometer, but I get very wrong results when I do FG reading (after applying refractometer formula). Refractometer is very well calibrated (checking it before every measurement), but I get results like 3.1% brix, which yields very low FG results, like 1.001. That sounds unfeasible for "normal" yeast like US-05.

Am I doing something wrong when doing refractometer measurements? Are there any "shorter" hydrometers available, that would require smaller samples?

Topic refractometer final-gravity small-batch hydrometer homebrew

Category Mac

1
answered at

I use a small hydrometer (17cm in length) and a 50ml test tube. I rarely need more than 40ml to take a reading, so four readings would require, in total, less than 5% of you wort.

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answered at

I find a refractometer works great for OG, and a finishing hydrometer works best for final gravity (with presence of alcohol). I typically drink the sample, as I am mostly curious as to how the flavor is shaping up, especially once FG has settled (to gauge bulk-aging or conditioning impact on flavor).

However, I have some sours that I sometimes return the sample with (since I take so many over the long aging period). In this case, I use a wine thief and I put the hydrometer in the thief. Before I take a sample, I put both in sanitizer, then carefully drain the sanitizer. Then, with the hydrometer in the thief, gently lower both into the vessel until I get enough of a sample to get a reading. Then I carefully pull out the hydrometer and gently set it aside, then return the sample to the vessel.

I know another homebrewer who constructed a container from about 3 feet of 3" diameter pvc pipe, sealed at one end and plugged on top, mounted on a stand, so he can keep his thief and hydrometer sitting in sanitizer. He just pulls the plug and empties the thief, then pulls his sample, measures it, returns the sample, then returns the thief and hydrometer to the sanitizer in the container.

Most thief's (thieves?) are plastic, so you probably don't want to leave it sitting in the sanitizer for extended periods, as the plastic will break down over time, but you probably also don't want a glass thief, as this will greatly increase the risk of breaking your hydrometer.

Good luck!

1
answered at

From morebeer.com: "After ethanol is present a refractometer reading will be off." That is, the refractometer is calibrated to measure sugar in water, not sugar in water/alcohol - the index of refraction is bit different for alcohol.

They provide a spreadsheet to help determine the actual gravity based on original gravity and final gravity reading.

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