Peroxide should be stored in a cool, dark place. Buy small quantities; it loses strength if stored for a long time. Do not use or store peroxide in metal containers, an amber coloured bottle is best and keep it in a cool dark but dry place. If you pour out too much peroxide, do not pour the excess back in the bottle as peroxide is easily contaminated basically the longer you have it once opened the weaker over time it gets Mr. Burns, I hope this helps.