The Tale of the Stuck Fermentations

A fermentation is “stuck” when it fails to reach the desired conversion level of sugar, usually coming to a halt somewhere below 10 °Brix. It does not refer to a failure to start, which is a different issue. I used to have a lot of stuck fermentations at home but really haven’t had a problem for the last decade or more as my techniques improved: Hydration nutrient, two-step nutrient addition and the like. But last year was a disaster in the basement — 30 gallons (114 L) of Traminette, 15 gallons (57 L) of Cayuga White, and 6 gallons (23 L) of Chardonnay stuck for reasons unknown (which is usually the case). I had to use every trick I knew to salvage them and I figured it would make a good lesson for other home winemakers. First, some background Brix is a density scale based on sugar in water, but it only indirectly measures sugar. Other dissolved solids like acids increase Brix, while ethanol (with a specific gravity of 0.790) decreases Brix since it’s lighter than water (which has a specific