A polysilicic acid containing fibrous material contains urea peroxide and bicarbonate and it is intended to be used in hair bleaching and particularly in making bleached stripes in hair. It is possible to cut patches of desired size off the fibrous material, which patches are moisturized with a solution containing urea peroxide and bicarbonate, and subsequently wrapped around the treated area of hair. As a result, properly bleached and intact hair is obtained. Ammonium bicarbonate is preferably used as the bicarbonate.