Jolie Kerr is a cleaning expert and advice columnist. She'll be here every week helping to answer your filthiest questions. Are you dirty? Email her.

I wish I had some hot tale to tell you since you have a filthy mind (as I do, too). But I have a new dark blue baseball cap that I sweat in and now it has a terrible salt stain on the brim. Can you help with any tricks to clean?

Thanks.

P.S. I do not have a dishwasher—I recently moved to my cabin in the woods.

It's true that I have a terribly dirty mind, and it's also true that I'm sitting here typing through a state of extreme envy that you not only have a cabin in the woods, but that you live there permanently. Are you my soul mate? What if this is the greatest meet-cute in the history of ever?!? I mean, you already know a bunch about cleaning because you know that "clean a hat in the dishwasher" is a thing.

Except you don't have a dishwasher, so that's not an option for you. I'm sorry for you that you don't have a dishwasher, as I am also dishwasher-less and feel your pain. But in this case, it's actually A-OK, because even though running a ballcap through the dishwasher is popular, in a folklore sort of way, when it comes to cleaning hats, that practice has a number of drawbacks. Among these drawbacks are the heat of the dishwasher, which can cause cotton, canvas, or wool to shrink and pucker and any plastic parts to melt. Also, dishwasher detergents often contain bleaching agents, which will lead to color loss. And then there's just the squick factor of washing a grimy ballcap alongside your dishes (of course, you can always run a load of just hats on their own, if you have enough).

The (Limited) Benefits of Dishwashing Your Hat

If, after all those dire warnings, you're still into the idea of using your dishwasher to launder your hats, put them on the top rack, which will keep them away from the machine's heating element, which is almost always on the bottom of the unit. The benefit of using the dishwasher versus the washing machine, which is also a good option, is that the dishwasher won't agitate the hat in the way a washing machine will, which means the bill, in particular, won't get bent as it bangs around in the spin cycle.

A Few Words on Using the Washing Machine

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Despite the fact that it's an imperfect method, machine washing ballcaps is definitely an option…unless you have a top-loading machine with a center agitator, because the fins on a center agitator will beat the hell out of that hat. You could certainly buffer the hat with a bunch of towels, but honestly? Dishwashing or hand-washing, which we're about to get to, are better options for those with top-loading washing machines.

But let's say you have a washer with no center agitator and you want to get your hat clean that way. Cool. Go for it—just follow these steps. Before you toss your hat in the wash, give it a thorough coating inside and out with a laundry pre-treatment spray like Zout, paying particular attention to the inside front of the hat. Zout is an enzymatic stain remover, so it will be the right choice for sweat-stained ballcaps. Use a cold or warm water setting and the gentle cycle, and allow the hat to air dry—don't put it in the dryer. A small towel balled up and placed inside the hat can help restructure it as it dries.

And the Best Method: Hand Washing

So sure, you can throw the hat in the washing machine, or in the dishwasher (providing you have one of those), but really hand-washing is a better choice, especially for nicer caps. I know that the idea of hand-washing sounds like a drag, but it's honestly super easy and mostly hands-off, despite its name.

  • The Setup: First, you need a place in which you can create a body of water in which to submerge the hat entirely. The kitchen sink is a good spot, but you could also use a large bucket, utility sink, or the bathtub. Just like with machine washing, you'll want to spray the cap with a stain treatment before you put it in the sink, which should be filled with warm (but not hot) water and a tablespoon or so of laundry detergent.
  • The Procedure: Submerge the hat in the sudsy water by swirling it around a few times, which will help the water and detergent to penetrate the fibers of the hat. Then just leave the thing to soak for a few hours. That's pretty much it! After two, three, four hours—however long you feel like leaving it, really—drain the water, which will be an insanely gross color that you should also feel free to admire because, really, the grossness of the water is sort of a marvelous thing. Then rinse the cap very well with cold running water. Once it's been rinsed free of suds, squeeze out as much water as you can (gently!), reshape the cap and allow it to air dry. Setting it near a fan or open window will help to speed that process up, as will stuffing the cap with a small towel.
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Mr Porter

Baseball cap ($125) by Ami, mrporter.com

Finally, a Warning…

Before we wrap this thing up, a final word about the development of those white salt stains: They're caused by sweat build-up, which you probably know, but you may not know that if you let them go too long without treating them, they can lead to permanent color loss. That Zout spray that I mentioned will be effective in treating them, as will dabbing white vinegar along the stained area in just the same way as you'd use vinegar to remove road salt stains from winter shoes. For very bad staining, multiple applications may be needed, but I also want to implore you to not let your hats go too long with white, salty sweat stains without being washed.