My mead is bubbling away in a primary fermenter, a large open topped container. At some point I’ll want to rack it to a secondary fermenter. That is, siphon the mead to a closed container where it’s protected from oxygen. There are two problems with siphoning mead or wine that is still fermenting. First, the carbon dioxide (CO2) in the mead will come out of solution and interrupt the siphon. Second, most of the yeast may have settled to the bottom of the fermenter, and they may be left behind. If there are not enough yeast in the secondary, they won’t complete the job. For these reasons, I like to leave my mead in the primary until it has fermented to dryness. I’ll be checking the specific gravity of my mead, and I’ll rack when it gets down to about 1.000.
Leaving the mead in the primary until it’s done risks oxidation, so it’s important to make sure the mead ferments quickly. Mead has a reputation for being a slow fermenter, and that’s why I use a starter, and stir every day. It’s why my mead recipes always include additives like DAP and cream of tartar. Most of my mead ferments to dryness in about two weeks.