Sweat stains and yellowing on white bogu become hard to remove once a long time has passed, so we recommend cleaning as soon as possible. Some white bogu have red felt in their core; in that case, cleaning may cause the red to bleed out and leave a pinkish tint. Coloring caused by this cannot be removed. Indigo coloring transferred from the uniform and navy coloring from the men-himo (mask cords) and similar cords are difficult to remove.