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Ask Dr. Laundry

Ask Dr. Laundry

Bleach and Hot Water

By Dr. Laundry January 4, 2011

Q. I learned from my mother, who was in the textile business for years, to never wash my whites in bleach and hot water due to the yellowing effect. I have to say that I have done my own bit of research on this over the years and have found my mother’s advise to be accurate. Every person that I have ever known to wash their whites in bleach and hot water had a slight yellowish ting. While their whites seemed white when held up against my whites, that are only washed in cold water and bleach, their whites no longer appeared white. I also learned from my mother that it is not the water temperature that washes the clothes but the detergent that you wash them in. Does The Clorox Company run test to see what water temperature is best for keeping whites their whitest?

A. Clorox does lots of testing to develop and improve its products, as well as determine the label instructions for the product packages. We test a variety of stains and soils for cleaning, as well as whitening and brightening. In addition, we test how our products work with different detergents, clothes washer designs, and in different water temperatures. That’s because there are three different forms of energy that accomplish cleaning and whitening: thermal (water temp), chemical (detergent/bleach), and physical (agitation). Your personal experience doesn’t match our laboratory test results based on average consumer wash conditions—all other variables being equal, we typically see improved cleaning and whitening in hotter water. It’s hard for me to know exactly how you do your laundry, and what differences exist between your wash habits and your friends’, but here are some thoughts on why you find your whites even whiter than your friends’ whites:

1. Amount of bleach used: bleach breaks down dirt and body soils into smaller particles, making it easier for the detergent to remove them, and it is important to add enough bleach to handle the soil load. Your friends may under use bleach—there is a big performance difference with ¾ of a cup of bleach compared to a ½ or ¼ cup, especially if they are washing large or heavily soiled loads.
2. When bleach is added: when you delay the addition of bleach, the brighteners in the detergent are able to deposit more effectively on the fabric. Brighteners are colorless dyes that absorb light outside the visible spectrum (light you can’t see) and reflect it in the visible spectrum. More light coming off fabric makes it brighter and whiter. Some clothes washers have dispensers that automatically delay bleach addition to make it easy for consumers to follow our “for best results” instructions: dilute ¾ of a cup of Clorox® Regular-Bleach in 1 quart of water and add to the washer 5 minutes after the wash cycle has begun agitating.
3. Water temperature and machine design: newer clothes washers add water from both the hot and cold lines to a “cold” load so that a pre-set consistent wash temperature is reached in every load all year long. This is especially important during the winter! So your cold loads may be warmer than you realize. And your friends’ loads may not be as hot as they think depending on what temperature they set their water heater at, and how far away it is from the clothes washer.
4. Choice of detergent: not all detergents are created equal, and some work better than others. Using a so-so detergent that doesn’t properly dissolve, isn’t shelf stable, doesn’t have enzymes and brighteners, or doesn’t have ingredients that prevent soil from redepositing on clothes will leave clothes dingy. There will always be an improvement with bleach compared to detergent alone, but bleach + a good detergent will always clean and whiten better than bleach + a so-so detergent.
5. Brand of Bleach: only Clorox® Regular-Bleach has patented “Whitest Whites” technology, including a polymer that ties up metals like manganese or iron to prevent them from reacting with the bleach and yellowing clothes. Store-brand bleaches do not have this.
6. Adding bleach to every white load: regular bleach users will have whiter whites than occasional users.

It sounds to me like you are a very conscientious bleach user, and I am not surprised you get such good results. For most people, using hot water is important to get the best results possible. But by carefully controlling the other variables, one can wash in cold water and get outstanding results, as you have found.