To get rid of those stains from the hat, you need to dip a toothbrush in white vinegar and apply the vinegar on the dirty areas. Then, put the hat in a mould and snap it into position. After this, put it in the top most rack of the dishwasher alone, add some bleach free detergent and let it to wash. Next, you should remove the mould and allow it to dry. To learn more about this process, you can visit.
Good news there is an answer! RAISE armpit stain remover works out all types of perspiration stains. It is the only solution available that actually removes yellow/brown/gray stains from clothing, hats, bedsheets. It was tested and endorsed by the Good Housekeeping Research Institute to purchase online go to www.armpitstainremover.com RAISE works on colored clothing as well but always spot check.