full image - Repost: Is sun tea dangerous? A field test. References added. (from Reddit.com, Is sun tea dangerous? A field test. References added.)
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After a discussion yesterday where people were curious about what would happen, I went ahead and added a candy thermometer to today's sun tea to see how hot it actually gets.tl;dr A couple of online magazines and blogs recently published warnings against sun brewed iced tea. The problem is none of them had any reliable reference other than a general purpose FDA warning about foods in the 40-140°F range. These blogs claim sun tea can't reach temperatures greater than 105-130°F but they provided nothing to back up those assertions.Those temperature claims looked suspicious because other things do heat up more than that. Official daily high temperatures are measured in the shade six feet above the ground under controlled conditions, and as we all know direct sunlight can be considerably hotter, particularly on pavement surfaces and inside of vehicles.According to the University of Georgia when the official daily high temperature is 91 F, the surface temperature of blacktop can reach 140 F. That's published as a caution to dog owners taking their pets for a walk.A network affiliate news program has warned viewers,When temperatures outside climb range from 80 degrees to 100 degrees, the internal temperature of your car can reach a scorching 130 to 172.In a separate report, another network news report explains the science behind why cars get so hot.Washington State University notes that backyard composting can reach internal temperatures of 135 F to 150 F at middle north latitudes. It even advises gardeners to be cautious and keep their compost below 170 F.So why would sun tea be unable to reach those temperatures?Today's experiment consisted of loose leaf Assam tea inside a steel infuser, put into a glass carafe of water. A candy thermometer was used to measure temperature. The carafe was left outdoors on a red brick surface on a sunny 101 F (38 C) day, and retrieved at half past two in the afternoon. The tea temperature was 150 F when I used kitchen tongs to get the thermometer and take a reading.For comparison, the University of Georgia reports that a red brick pavement reaches 135 F on a 91 F day.It surprised me a little the tea wasn't hotter because it had both the brick surface temperature and internal re-radiation to warm it up. As the tea darkens it could also be expected to retain increasing amounts of heat. It may or may not make a difference that the surface of the glass carafe had curves that could have a magnifying effect. Yet 150 is still comfortably above the upper limit of the FDA's warning range.If your local temperature doesn't rise to triple digits, then extrapolating from the U of Georgia's findings you'd probably reach a safe temperature by placing a black mat beneath your tea on a sunny day in the mid-nineties.If you'd like to try a similar experiment and add your results in the comments, then we can compare notes.Here's hoping this helps.And u/rage242 who started yesterday's discussion you're probably OK doing this in Arizona.
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