How To Use Hydrometers and Refractometers
Many new mead makers want to count bubbles as an indicator of fermentation. While this does tell you CO2 is being released, it is not a good indicator of fermentation progress. CO2 can be continually released from mead for months after fermentation is done.
Also, NOT seeing bubbles could just mean your fermentor is not sealed. Testing gravity is simply the only way to be sure your ferment is progressing as it should. Gravity can be read by several tools I will now describe.
Hydrometer
A hydrometer is the easiest way to determine the gravity of your mead. You simply let the hydrometer float and read where the meniscus line is on the hydrometer. If you are concerned your hydrometer is wrong, simply float it in water. Water should always read 1.000. This is also a good way to make sure you are reading the hydrometer correctly.
In many cases, I simply leave the hydrometer in the mead to get constant readings. You can also pour the mead into a sanitised beaker if your fermentor is not deep enough. Just pour the mead back into the fermentor post-measurement! (Or drink it. I won’t judge.)
Refractometer
Refractometers are a wonderful way to monitor gravity because they only require a drop of mead. The downside is that once alcohol is produced, you must correct the reading using a calculator. Once you understand this, it is very simple to do.
Handy online calculators exist to make these calculations very easy to do. I currently suggest this one: https://www.northernbrewer.com/pages/refractometer-calculator
So how do you know the ferment is done? It really depends on how you make your mead. Here are some good indicators:
Gravity below 1.000: The mead has no sugar left to ferment. It has to be finished.
The gravity has been stable for several weeks AND your yeast is at its max ABV. If your yeast has not reached max ABV, you may have a stalled ferment. I suggest you attempt a restart or stabilise if it tastes good. This category is notorious for creating bottle bombs. Do not bottle as is!
The gravity is stable AND you stabilised.
