I’ve asked the following question elsewhere and gotten a variety of responses, mostly unsatisfactory because they seemed based on the outdated lore of home economics or purely anecdotal evidence. I’d like a bit more science (or other objective evidentiary basis). Nothing is riding on this except the cleanliness of my family’s clothes.
“The conventional wisdom is that washing clothes in hot water is more effective at cleaning them than washing at lower temperatures; however, I’ve also read that you shouldn’t wash freshly-stained clothes in hot water because the heat will “set” the stain, making it impossible to remove in the future. How (if at all) can both of these be true?”
To extend the inquiry a bit –
People seem to buy into the idea of “cold-water” detergents which sounds to me like they’ve been conned by the marketers of such products. What is it that detergents marketed for cold water use could not do better in hot water?
Is there any evidence that hot water washing is any harder on clothes than, say, warm water? Isn’t it really the agitation action of top-loading machines plus the heat from machine-drying that really shrinks and reduces the life of clothes?
Does hot water washing really make a difference (i.e. cleaner laundry) only if it’s much hotter than “hot” tap water (like the boiling water people used to sanitize their linens in)?
Any insights would be much appreciated! If I don’t need to run up our energy bill and ruin the environment by using hot water, I’ll stop doing it!
Stains can be a variety of substances, but there is nothing inherent in hot water and setting of stains. Allowing a stain to dry is the only bad idea- and this is a logical one in that if the stain material is allowed to dry and compact it becomes harder to wet the stain as well as allow the enzymes to access the material. (This is very similar/related to the concepts behind the difficulty in cellulosic ethanol and obtaining sugars from non-food sources.)
The makers of Tide just did a cradle to grave analysis of the carbon footprint of their detergent. The conclusions were something like 5% for the product, 25% getting the product to the washing machine, and >50% heating the water. So the question is not necessarily washing clothes better, but how much do you hate the environment?
With that in mind, detergents and in particular the enzymes in them are optimized for high temperatures, it is a >$100B goal to develop detergents and enzymes that work at room temperature or lower and perform as well as the existing enzymes. The cost savings to the consumer would be enormous, the opening of markets to other countries without hot (or any) water, and the decreased CO2 would be enormous.
But yes, companies are striving to develop lower temperature detergents, but it isn’t easy and it will take some time before they are all of the way there.
So your questions effectively miss the major implications of such technology, but interestingly your final comment captures the bigger long term goal!
About the only thing I wash in hot water is some old oily towels and rags that I use for cleaning and working on cars and bikes.
I wash almost everything in cold water. This helps stop shrinkage. I use ‘free’ detergents without any extra fragrances or anti-static properties. A lot of my clothing is made of technical materials and such fragrances, fabric softeners and dryer sheets can clog up the sweat wicking properties of such materials. I have used the special ‘cold’ detergents, but haven’t noticed noticed any real difference yet.
I also line dry a lot of my clothing to save costs. I even have a place to hang clothes in my garage during cold or wet weather.
Care labels: most of my clothes say machine wash in warm water on xyz cycle. Some have an indecipherable series of supposedly universal symbols I don’t understand so I treat them like similar items with an understandable label. I don’t use hot because the folks who make my clothes say not to use hot water, and it doesn’t seem contrary to my best interests (i.e. increased wear causing me to buy more of their clothes).
Consumer Reports says the clothes washed in cold with detergents formulated for cold water are just as clean as those washed warmer. It’s not ad-hype.
They also say you generally need a lot less detergent than advertised. So, the measuring cup the detergent company says you should use is indeed ad-hype.
