I measured the specific gravity (SG) of my fermenting mead yesterday, and it came to 1.046 @ 64 degrees Fahrenheit. So fermentation is about halfway done.
Temperature affects the measurement, so it’s important to record and adjust for it. Hydrometers are calibrated to work at a particular temperature, 60 degrees Fahrenheit (about 15.5 Celsius) in my case, and come with a table that shows you how much to adjust your measurement for higher or lower temperatures. 64 degrees is close enough that no adjustment is required, but my reading was still off because of the suspended CO2 in my fermenting mead.
The sample I took had some froth on the surface, so I could actually see this CO2. It provided some “lift” to the hydrometer and made it float a little higher than it would have, so the actual SG of my sample was a bit less than 1.046. I could have “degassed” my sample by shaking/stirring until it didn’t bubble anymore or microwaving it until it started to boil then cooling it right away. My measurement would have been more accurate then. I just wanted a rough idea of how far along the fermentation was, so I skipped that step.
This little exercise was all about answering the question, “is it time to rack?” The answer is: Not yet.
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