About 12 hours at room temperature. You're welcome.
Want to know more? Oh, thank goodness. We did a lot of work on this.
How cold is cold?
Whenever you see claim that a container will keep something cold for however many hours or days, you have to know two things:
- What is their definition of cold?
- What are the environmental conditions? It other words, what is the ambient temperature and what other sources of heat (like the sun) is the container exposed to?
For our experiment, we defined "cold" as less than 50 degrees Fahrenheit. Beer is typically served at 37 to 39 F, which heavier styles like porters and stouts perhaps a touch warmer. We put a stainless steel vacuum insulated growler in the refrigerator for a while so the steel would be the same temperature as the 64 ounces of chilled water we then poured into the growler.
We then inserted the thin wire probe of a thermocouple thermometer into the growler and clamped the lid shut. The thin wire and the growlers thick silicone gasket minimize the risk of infiltration by outside air.
For this first test, we kept the growler in a room that was about 75 degrees and recorded the temperature of the water in the growler every hour. The water started at 40.1 F and the temperature increased by an average of 0.8 degrees per hour. After 12 hours in the growler, the water was at 49.6 F.
Note that we believe the probes of our thermometer were causing it to read about 3 degrees high. We've ordered replacement probes and will repeat this experiment once they arrive. However, we do believe that the temperature readings were consistent among this set of data and that the change in temperature measured is accurate.
