How Do I Clean a Flask, Anyway?

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Jolie Kerr is a cleaning expert and advice columnist. She’ll be here every week helping to answer your filthiest questions. Are you dirty? Check the Squalor Archive for assistance. Are you still dirty? Email her.

No matter what I do, I can’t seem to get my flask to smell like anything other than the combination of every alcohol I’ve ever smuggled into a ballgame/concert/spin class. I don’t know if you’ve covered this in the past, but it seems perfect for one of your columns.

I mean, flask-cleaning does seem perfect for one of my columns. And yet? You’re the first person to ask about it. And, since it’s wedding season, and flasks are an exceedingly popular groomsman gift, this feels like the right time to take this topic on. So let’s do this thing.

The instructions for cleaning a flask are going to be pretty similar to those for cleaning travel mugs and bongs. The idea is that you want to use a combination of things that can, essentially, do the scrubbing for you, since you can’t exactly reach inside the flask and scour away with a Dobie Pad. Even the use of a bottle brush is probably not going to be an option, given the way flasks are designed: The brush won’t be able to get into corners where old booze likes to linger around, getting sticky and gross.


Before we get into how to clean an older flask that’s got some buildup or is retaining a smell, I first want to encourage you to wash a new flask before using. I know, I know! It’s kind of a drag to ask these kinds of things of you, but seriously, you should really get in the habit of washing new things before using them. God only knows what’s in them! Why, just the other day I found a dead grasshopper in a tub of arugula! These things happen.

If the flask is new, it can be washed with plain old soap and water—just be sparing with the amount of soap you use, since rinsing a flask out can be a bit tedious. Boiling water is a great rinsing agent, but use caution so you don’t burn yourself; wrap the exterior of the flask with a dish towel so you can hold it tightly even if the hot water causes the metal to heat up, and use a funnel to avoid splashing yourself.


For older flasks, a bit more scrubbing power will be needed. This is where a lot of our bong- and pipe-cleaning techniques will come in. The idea is to use something that will create some friction up in there (kosher salt, rice, a denture tablet, epsom salts, baking soda) combined with a liquid (water, rubbing alcohol, white vinegar, vodka, lemon juice) to aid in cleansing. The only caution I would give about the use of denture tablets, in particular, is that it may leave behind a bit of mintiness. Maybe you will not mind that! Fill ‘er up with some bourbon and call it a mint julep.

Once you’ve picked your combination of cleaners, put them in the flask, leaving at least a quarter of the flask empty for headspace. Then cap the thing up and shake shake shake shake shake for 20-30 seconds. This will feel like an eternity. But you really do want to give it a vigorous shaking so that the interior walls and tight little corners get treated to a really good scrub. Then be sure to rinse well, remembering that boiling water is particularly excellent when it comes to tricky flasks.


If you notice a lingering odor … do I still need to tell you? You know. I know you know. Okay, fine, for the newbies: White vinegar will be the ticket. Also, lemon juice! Gotcha, didn’t I? What can I say, I like to keep the romance alive.

Before we move on to what to do about keeping the exterior clean, it’s important to mention that you should avoid using chlorine bleach to clean a flask, as the bleach can be corrosive to stainless steel. When it comes to the exterior, you should take into account what the flask is made of before cleaning, i.e. if it’s silver-plated, use a silver polish; if it’s leather, be sparing with water when cleaning the exterior, and have a towel on hand to quickly wipe up spills and splashes. (For badly stained leather-wrapped flasks, try a bit of saddle soap.) For stainless steel, which is probably the most common, avoid using any kind of abrasive cleaners or scouring pads, which will cause scratching. Microfiber is a good material to use for drying stainless, because it will wipe away any fingerprint marks and streaks that so commonly befoul that metal.


Once you’ve cleaned the flask and it’s time to dry it, there are two things to do. The first is to set the flask upside-down, with the lid open, on top of a dish towel or in a drying rack. The second drying option is kind of a cool one: Tightly roll up a paper towel and insert it into the opening of the flask and just let it chill there overnight; the paper towel will absorb the moisture. (It’s okay if you don’t think it’s as cool as I think it is—we can still be friends.)

In closing—and I know you’ll hate me for this, but it’s my job to remind you of these things—rinsing your flask out after using takes only a few seconds and will save you a lot of work down the line.


Jolie Kerr is Deadspin’s resident cleaning expert and the author of the book My Boyfriend Barfed in My Handbag … And Other Things You Can’t Ask Martha (Plume). Follow her on Twitter, or email her:


Illustration by Sam Woolley.

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