Fermentation Failure: Too Hot or Too Cold
Ideal Wine Fermenting Temperature
Wine Yeast like to ferment between 70-75 degrees Fahrenheit--72 degrees being ideal. Fermentations that are too cool may become very sluggish and quite often will not ferment at all. Fermentations that are too warm can perform poorly as well. And in extreme cases--85 degrees and above--the wine yeast cells may become damaged, inhibiting their ability to ferment.
It is also important to note here that fermentations that are too warm are more hospitable to the growth of unwanted micro-organisms. This could result in off-flavors in your wine and in extreme cases complete spoilage.
Having a consistent temperature throughout the fermentation is important as well. Room temperatures that fluctuate on a daily bases can play havoc on a yeast's ability to ferment. Simply put, the more the room temperature fluctuates, the more likely you are to have a problem fermentation.
Avoid trying to ferment your wine in places such as detached garages, attics or spare bedrooms where the room temperature can easily be ignored or not controlled at all.
If your house has a basement, it is usually one of the better places to ferment your wine. Basements typically maintain a temperature that is more constant than the rest of the house.
However in the winter months, basements can become too cool. If this becomes the case, a mild heat source such as a nearby light bulb may be enough to solve the problem. Also try to keep your fermentation vessels up off the cold basement floor. Instead, keep your fermentation vessels elevated on a table or shelf.
Using a Thermometer for Wine Fermentation
One way to keep a handle on your fermentation temperature is to use a thermometer. If you are using a pail as a fermentation vessel, you can use a floating thermometer directly in the wine. Just lift it out when you want to take a reading, otherwise it stays in the juice.
Or, you can use a crystal strip thermometer which sticks to the outside of the fermentation vessel. The temperature illuminates by what appears to be magic. Just a quick glance and you are able to tell the temperature of your fermentation.
For more information on the thermometers we offer, go to Fermenting Thermometers.