The use of hip flasks, a container contoured to hold distilled beverages and fit snugly in the pocket next to the hipbone, dates back to the Middle Ages. During America's prohibition of liquor sales, many individuals elected to carry a hidden hip flask in order to secretly enjoy their favorite illegal libation.
Hip flasks are back in vogue today, usually constructed of stainless steel or silver and often monogrammed with an individual's initials or some special commemorative message and given as a gift. They are especially popular among sports fans who sit out in the stands during chilly and inclement weather, fortifying themselves with a sip of whiskey, bourbon or vodka secreted away in the flask.
Although their very slim construction makes this container easy to transport and easy to drink from in a discreet fashion, that same construction makes it a bit challenging to clean unless you know some simple tricks to keeping a hip flask clean.
The secret to keeping a hip flask clean is good old fashioned vinegar, that clear, pungent liquid you can find at the grocery store. Create a cleaning solution by mixing one cup of tap water with one cup vinegar.
Next, you want to bring two cups of plain tap water just to a boil and pour some into the flask, rinsing out the inside of the flask before pouring it down the drain. Use hot tap water if you don't have access to boiling water. The metal of the flask is likely to get quite hot, so be sure you are handling it with pot holder gloves or a thick towel so that you don't burn your fingers while swishing the hot water around inside the flask.
Now you're ready to pour in about half a cup of the water and vinegar mixture. Put the cap back onto the flask and shake for about 20 to 30 seconds. Pour out this solution from the flask, refill the flask with hot boiling water and swish around and dump that water out. Now pour another half cup of the water and vinegar solution into the flask, recap it and shake for another 30 seconds. Pour out that solution and rinse the inside of the flask with warm water once or twice to make sure you've removed any traces of the water-vinegar cleaning solution.
Position the flask on a dish drainer so that it's narrow opening is pointing straight down and let any residual water from inside drain away overnight. If your flask is sterling silver, this is also a good time to polish the outside surface with a good silver polish to remove any tarnish. Your hip flask is now ready to be refilled with your favorite alcoholic beverage.