D+Caf Caffeine Test Strips /// $9.95 for a tube of 20 strips

The Promise: A test strip that quickly tells you if a beverage is caffeinated or decaffeinated. The purpose of the D+Caf test strip is to give caffeine-sensitive (or just curious) people the ability to label their coffee as regular or decaf. Silver Lake Research Company, the maker of the product, claims D+Caf is "easy to use, provides quick results, and has the same accuracy rate as professional laboratories (98+%)."

Is it? Let's find out.

Background: Caffeine levels in regular coffee can shoot from 75 milligrams to 150 mg per cup depending on the variety of the bean, and consumers tend to opt for decaffeinated coffee over regular about 20 percent of the time. The FDA states that at least 97.5 percent of the caffeine in coffee beans must be removed for a drink to be labeled as decaf, but says nothing about the actual amount of caffeine left in the drink. So, while the average cup of decaf contains between 6 and 10 mg of caffeine per serving, the regulation allows for "decaf" coffee to contain much higher levels of the stimulant, at least 30 milligrams in some cases, according to Consumer Reports. D+Caf strips consider a 6-ounce drink that contains up to 20 mg of caffeine as "decaf" and caffeinated as anything over 20 mg.

In Practice: You can't use D+Caf strips on just anything: they aren't made to work once a beverage has milk or sugar in it, so we couldn't test it on Coke, a sweetened chai latte or even a plain cappuccino. Instead, we used a sample set of six black coffees and five unsweetened teas. These included coffee from PM's kitchen coffee machine (which makes Flavia-brand coffee), Starbucks-brand brewed coffee from the building's company cafe, Starbucks brewed coffee from a nearby location and five blends of unsweetened bottled Teas' Tea with varying levels of caffeine. We also tested the strips on filtered water as a control.

Using the strips is easy: You just dip 1/8 inch of the strip into the beverage and wait 30 seconds. Reading the results isn't quite as simple.

The strip we used to test the water clearly showed that the beverage did not contain caffeine with a bold line on the decaf side and only a faint hint of mark on the caffeinated side. However, the results we got for the coffee and tea samples were more difficult to decipher because they showed 2 lines of similar darkness. After some serious eyeballing we noticed the slight differences between the lines: in general, the results of the decaf cup displayed a darker line on the decaf side, and the results of the caffeinated cup displayed a darker line on the caffeinated side.

The strips, while not easy to read, generally correlated with the decaf or regular label on the coffee or tea. The decaf coffee from our kitchen, the company cafe and Starbucks were all, according to the D+Caf strips, decaffeinated. The test strips from the different types of tea, with caffeine levels from 15.9 milligrams to 28.2, all produced expected results of decaffeinated and caffeinated, except for the strip for Pure Green. We tested two bottles of the Pure Green tea, which both produced a decidedly "decaf" result, even though the company website reports the Pure Green tea to have 21.2 milligrams of caffeine. According to Rona Tison, vice president of corporate relations of the company that makes Teas' Tea, the decaf reading could be correct since the tea is produced in an organic way that allows each brew to contain varying levels of caffeine.

The Bottom Line: if you're worried that your waiter got confused when brewing your after-dinner espresso, D+Caf is a useful product to keep on hand. But, if you want to monitor anything subtle, like the amount of caffeine in tea or the exact amount of caffeine you're ingesting, the imprecise results of D+Caf just don't cut it. —Allie Haake