A while ago I read your column concerning the effects of hot tea on styrofoam cups. Being an avid tea drinker myself, I was reminded of something. I work at the local public library where, in the staff lounge, there is an automatic dispenser for boiling water. When it broke recently, I had to start microwaving my water instead. But when I empty my packet of Sweet ‘n Low into the mug after microwaving the water, it bubbles and fizzes as if some strange chemical reaction were going on. This never occurs when the water comes from the dispenser or is boiled in a kettle on the stove. What are the microwaves doing to my Sweet ‘n Low? I’m worried! –Fred Kuhr, Evanston, Illinois
I never did trust that Sweet ‘n Low stuff. For that matter, anything with “‘n” in the title has got to be on the suspicious list. But there’s nothing special about Sweet ‘n Low that causes it to effervesce, as we weens like to say. (“Bubble and fizz,” indeed. How do you expect to get anywhere in science with a vocabulary like that?) Sugar and salt produce equally vigorous reactions, as will just about any powder except flour, which just sort of lies there.
Here’s what happens. When you put a kettle on a conventional stove, some of the water at the bottom turns to steam, making bubbles that float to the surface. But the bubbles don’t form just anywhere. At the outset they need to latch on to tiny crevices on the kettle’s bottom or sides until they can get big enough to make it on their own. These crevices are called nucleation sites. (A related phenomenon is the condensation nuclei–dust particles, usually–that water vapor needs in order to form raindrops.)
In conventionally boiled water, there’s a certain amount of internal motion called convection–the hot stuff at the bottom becomes less dense and rises while the cooler stuff sinks. Convection brings more water into contact with the nucleation sites, so the bubbles get bigger faster. Microwaved water, however, heats up uniformly. Since there’s no convection, bubble formation is pretty limp. Without bubbles, the water heats as much as seven or eight degrees Celsius above boiling point without actually boiling, a process called superheating.
So what happens when you dump in the Sweet ‘n Low? Instead of bringing water to the nucleation sites, you bring nuclei to the water. It’s like seeding the clouds. All the superheated water that’s been sitting around in frustration, unable to vaporize, suddenly gloms onto the nearest particle, forms bubbles, and rises to the surface. Result: fizz galore. Play your cards right–you want to get the water as superheated as possible without actually boiling–and you can get the water to erupt and scald everybody within a radius of three feet, providing numerous opportunities for lawsuits. (There have already been one or two cases, I’m told.) Another money-making opportunity from your friends at the Straight Dope.
What is the origin of the design known as “paisley”? Most patterns have some basis in nature, such as flower patterns, leaves, etc. A paisley looks like some sort of amoeba. What is a paisley supposed to be and how did it get that way? –Rob Marchant, Carrollton, Texas
You probably think paisley originated at the same time as the Beatles, Peter Max, and the Summer of Love, but that’s because you lack historical perspective. Paisley is actually an ornate pattern that was commonly used for 19th-century shawls manufactured in the town of Paisley, a textile center in Scotland. The Scots stole the idea from similarly patterned cashmere shawls made in Kashmir from goat fleece (cashmere-Kashmir, get it?), which began to be imported from India around 1800. The traditional explanation for the commalike paisley motif is that it’s a pine cone, but if so it’s the damnedest pine cone I ever saw. Textile historian Martin Hardingham has a better idea; he says it’s “more directly identifiable with the cashew fruit and seed pod which has been a symbol of fertility for thousands of years.” Ergo, sex is at the bottom of it. My mother always suspected as much.
Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.