Making "sun tea:" glass or black container?

So, lots of people like to make “sun tea” in warmer weather. To wit, put a glass pitcher in the sun with a bunch of tea bags or loose tea of your choice, cover, and wait a few hours. Result: warm tea that can then be sweetened and served over ice. Now, presumably, the reason for brewing in the sun is to generate some warmth in the water to better brew the tea in a reasonable amount of time, while avoiding turning on the stove on a hot day. Tea will “brew” in room temperature water, but it takes a long time.

Question: Why not put the water and tea in a BLACK container? Wouldn’t this heat up much faster in the sun and therefore brew faster? You wouldn’t have to let it get very hot (thus necessitating more ice or warmer iced tea in the end). Sure, the tea looks pretty in a nice glass container all lit up by the sun, but if we’re looking for practicality, a black container would win, hands down. What’s wrong with this reasoning?

Nothing, I think, except that glass containers and pitchers might be more common?
In my experience this is usually made in fairly large quantities – I can’t think of an appropriately sized dark/black container off the top of my head. Perhaps using foil to create a reflector oven type arrangement would have a similar effect? I think this might call for an experiment…

Because sun-brewing won’t get the water temp high enough to kill bacteria, a safer method is to skip the sun-brewing step and place the brew vessel directly in the fridge. Here’s why, and a recipe:

clear on the sun side and black on the opposite side will collect the most heat. an all black container would work better than all clear container though seeing the strength of the brew is then not as easy.

My first response to this was “What bacteria?” If I’ve got bacteria in my tap water that’s going to grow in warm temperatures, I think I’ve got bigger problems. Then I read the snopes article, and understand that if I’m using not-that-clean vessels for brewing, it could harbor bacteria. Still, I’m the kind of guy who fills a glass of water from the tap, drinks have of it, and then leaves the rest sitting on my bedside table over-night, whereupon I drink the remainder in the AM. No bacteria yet.

Then I realized that maybe it’s that the tea provides enough food for the wee beasties to multiply rapidly, or maybe even harbors some to begin with. <shudder> Guess I’ll go back to nuking the water and drinking a bunch of radiation. :slight_smile:

The fear of bacteria in sun tea is way overblown. People have been doing it forever and no one gets sick from it on a regular basis. Don’t put the sweetener in until after brewing and I think you’re fine.

Also try to stay away from tea bags containing Spanish cucumbers and German sprouts and you’ll be in even better shape.

I think it’s smart to know the potential exists for bacterial contamination. You might want to dump sun tea accidentally left out overnight, and you definitely want to clean the container between uses.

But it’s not the kind of thing I’d spend any more time worrying about than that.

FWIW A way of making water safe (safer?) to drink is to put it in a clear container and expose it to the sun for hours (don’t remember how long, but it’s quite a long time). Something to do with UV light, which a black container would block. Usually used in a back country hiking/ backpacking trip or for survival.

Are you thinking of solar water disinfection?

Well, I find that sun tea gets ropy in just a couple hours. I also find that regular (hot or iced) tea goes bad overnight if left out.

Huh. So putting contaminated water in a clear bottle in the sun for six hours will disinfect it (a literature article about that beyond the cite already offered) but for some reason putting water and tea bags in the bottle (tea, which per the Snopes article, has caffiene which should further kill off bacteria) allegedly does not.

Interestingly enough Snopes does not cite an actual CDC article or source, just some newspaper articles that must make the same claim. Searching the CDC site I can find no articles on sun tea, nor on the exact germ discussed in the article causing disease. Even others of its genus have little coming up on searches in the medical databases and those mostly among the immunosuppressed. (Like this one.)

This time Snopes is a fail. Sun tea does not present any significant health risk. It actually would disinfect the water at the same time.

Wait, “ropy”? I’m imagining viscous strands of bacteria and becoming slight nauseous. I’ve never seen tea go “ropy” and I’m not sure I want to. Are you talking about sweet milky tea?

Is it possible that the container is a factor? SODIS uses PET bottles while sun tea is generally made in glass.

Well first of all is the point that there is no cite that the CDC actually ever said such a thing and there are no case reports of illness from sun tea or from that particular organism. This point is simply that Snopes screwed up and believed some newspaper articles that claimed that the CDC said something without checking for a more primary source. After I posted I looked a bit more and found this teageek entry that had dug more and got a response from the CDC stating that there is no CDC guidance on sun tea and tracking how the myth was born. As they concluded:

Is a glass bottle as good to disinfect water as a plastic bottle, if you are starting with contaminated water to make your sun tea? I’m not sure. Glass, I think, blocks UV more than the plastic does, so maybe not. So yes, if your water is contaminated to begin with it may, theoretically anyway, be safer to use a plastic bottle.

That was an informative link, thank you.

Yeah, UV sterilizes by disrupting DNA (specifically, cause neighboring thymine bases to dimerize). DNA has absorption peaks at 265 and 185 nm, so lower wavelength UV light (UVC) is most effective.

Here’s a transmission curve for various types of glass, and here’s one for borosilicate glass that shows more detail at the UV range. Commonly used soda-lime glass is fairly opaque at the lower wavelengths wavelenghts.