I often wear baseball caps when I'm working outside my house. In weather like we've had recently (95 degrees Fahrenheit and 90 percent humidity), these baseball caps are often stained with sweat.
A couple of years ago, my wife and I started using a Ball Cap Buddy to wash stained baseball caps in the top rack of our dishwasher. Most of the caps have come out as good as new. However, I've recently had problems with a couple of black hats changing color to a distressed brown after washing.
When the first hat was discolored in this manner, I thought it had something to do with the material that made up the hat. After a second hat was discolored in the same way, I started looking for a difference in the cleaning process we were using.
It turns out that the dishwasher detergent we are currently using, Cascade with ShineShield, contains potassium hydroxide, sodium hydroxide, sodium silicate, and chlorine bleach. This works very well on everyday dishes, but it obviously discolors baseball caps that are colored certain types and colors of dyes.
I like using the Ball Cap Buddy in the top rack of the dishwasher, but I think I'm going to try using it in the clothes washer instead. It's unlikely that laundry detergent would discolor black baseball caps the way that our dishwasher detergent does.
If you decide to use a Ball Cap Buddy on the top rack of a dishwasher, check the ingredients in your dishwasher detergent to ensure that your caps won't get discolored like mine did.