Can I just put a ball cap worn while sweating in summer into the washing machine?
During seasons with heavy sweating, the inside of the hat quickly gets wet, making one think of washing first. However, because a cap has a brim, it is hard to judge whether it can be treated like regular clothing.
Remaining sweat can cause discoloration, so it is better to dry it each time, and washing is instructed as hand washing.
What to pay attention to first regarding summer ball caps is the amount of time sweat stays on the cap rather than the washing method. Centaur's big logo ball cap sky blue is guided as a product where color transfer, discoloration, and bleaching can occur upon contact with oil, moisture, or sweat, or when friction occurs[1]. Changes such as color transferring or fading are difficult to reverse once they happen.
Washing instructions can be confirmed from the big logo two-tone ball cap brown of the same line. The details state to hand wash in water not exceeding 30°C, do not bleach, dry flat in the shade, and avoid tumble drying[2]. Drying flat is because hanging it while wet easily distorts its shape as the weight shifts to one side, and prohibiting tumble drying is because heat and rotation ruin the shape of the brim core and crown.
Therefore, on days with a lot of sweat, rather than increasing washes, it is better to take care of it right after wearing. Pressing the inside sweatband with a dry towel to remove moisture, and storing it after drying completely in a well-ventilated shaded area is generally recommended. Situations where it is pressed and folded or rubbed inside a bag, or where a dark-colored cap stays in contact with light-colored clothing collars for a long time, are also conditions prone to friction and color transfer.
hmmm, this guidance reads closer to addressing habits during wear rather than how to do the laundry.
How often it is good to wash a sweat-soaked cap has not yet been confirmed.