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Ask Dr. Laundry

Ask Dr. Laundry

Hot Water and Bleach

By Dr. Laundry October 19, 2010

Q. I have a friend who told me that in college he was told that hot water makes bleach less effective. Is this true? I always wash my whites in the hottest water. Thank you for your input.

A. Thanks for the great question. Here is what I would tell your friend: washing white and safely bleachable colorfast items with Clorox® Regular-Bleach in the hottest water possible will give you the best cleaning and whitening performance because its effectiveness increases with temperature. Perhaps you would like to avoid an “I’m right, and you’re wrong” gloating response to his opinion (not really good for a friendship) by applying what he was told to the proper storage of bleach. In that case, he is correct: Clorox® Regular-Bleach should ideally be stored at room temperature (70°F) because the active ingredient in liquid bleach, sodium hypochlorite, is very sensitive to high heat storage conditions. Basically, you want to store it at normal room temperature to prolong its active life, and when you add it to a load of laundry, use hot water because you want it as active as possible for the best performance. As a bleach user, he definitely sounds like a friend worth having!