The last thing you want is for your fire engine red hat to come out of the washing machine a pale pink colour. And just think of all the poor white socks! So before you hastily wash your headgear, check to make sure the colour will stay put. With most newer hats, you won’t have anything to worry about, but it’s best to err on the side of caution and test them just in case.
There are two ways you can check for colourfastness. The first method is to simply rub the hat forcefully on a white sheet of paper. If no colour transfers to the paper, your hat’s good to go in the laundry. The other way you can check is by taking a white piece of fabric, dipping it in a mild detergent, adding some water and rubbing it on the inside of the cap. If the area doesn’t fade and there’s nothing to be seen on the white piece of fabric, then you’ve got the green light.