By definition, water has a neutral pH, 7.0, which is neither acidic nor basic (alkaline). To make an alkaline solution in water is easy. All it takes is the addition of a base. Even a small amount will do, as any pH above 7.0 is considered alkaline. It doesn’t start eating the flesh off your bones until it gets a few notches up the pH scale, thankfully.
If you plan to work with strong alkaline solutions, I urge you to wear gloves and goggles. Alkaline solutions feel slippery on the skin, but they do not give a burning sensation as they eat through you. This is because they quickly destroy nerve tissue, so no pain signal registers even as they “burn” through to your bones. You may wish to wear a lab coat or apron as well, as base splashes can discolor and eat holes in your clothing.
At home, there are a few common sources of bases. Bleach is a solution of sodium hypochlorite a base in water. Ammonia glass cleaners are ammonia gas dissolved in water which forms ammonium hydroxide a base. Drain clog removers like “Liquid Plumber” usually contain bleach and sodium hydroxide both bases in water. Be sure to read the labels on these though, since some brands choose to use an acid solution instead.
In the chemistry lab, bases are easy to come by. The most common are the hydroxides, with sodium hydroxide and potassium hydroxide topping the list. Bubbling ammonia gas through water produces ammonium hydroxide in solution. The addition of an alkali (group one) metal such as lithium or sodium produces the aforementioned hydroxides, liberating hydrogen gas in the process. As this can be explosive, take proper precautions. Placing a layer of oil atop the solution keeps oxygen away from the reaction site, making ignition less of a hazard. (Thanks to Flinn Scientific for that tip: http://flinnsci.com) The addition of weak ionic bases (acetates, sulfates, carbonates…) or organic bases (amines, among many others) will also render your solution basic.
Should you ever find that your alkaline solution is too basic for whatever purpose, you can remedy the situation by adding some acid. At home, you can grab vinegar (acetic acid in water), lemon juice (citric acid, and a little ascorbic acid, in water), CLR (a mix of acids), an acidic drain opener (mostly hydrochloric acid in water), or even a sour gummi candy (they’re coated in citric acid). You might want to look into Helium’s article on making a red cabbage pH indicator if you’re playing around with pH. For the sake of this article, I’ll assume that the chemist in the lab knows where to find the acid cabinet.