Visiting my parents, my mom seems disappointed to find me washing my clothes in cold water, she says it’s just not right but couldn’t quite explain why.
I’ve washed all of my laundry using the “cold” setting on washing machines for as long as I can remember. I’ve never had color bleeding or anything similar as seems to affect so many people.
EDIT: I love how this devolved into tutorials on opening Capri suns, tips for murders, and the truth about Australian peppers
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Once upon a time, detergents didn’t work so well in cold water. Washing machines had cycles like “Cotton 140F” and “Delicates 100F” and that was how your mom grew up. If you washed in cold water it didn’t work well at getting your clothes clean, and it didn’t rinse well either.
Since she grew up there have been huge improvements in detergent efficacy and you can wash really well in cold water, which is much cheaper for your energy bill and better for the environment too. Far from doing something wrong, you’re doing it right!
It does make a bit of difference for certain types of dirty clothes. Deodorant stains come out much easier in hot water, oil stains also come out easier in warm water in my experience
A rule of thumb in chemistry is that for every increase of 10°C reaction rate doubles. Those numbers are never precisely right but it’s the right ballpark for practical situations, if you start doing experiments on the surface of Venus you would probably need a different heuristic. it’s also true for physical reactions like dissolving things in water. So hot water dissolves things faster than cold water and all detergents would work faster in hot water than cold.
With modern detergents the cold water works well enough that it’s not worth the energy to heat the water up. With older detergents you needed the higher reaction speeds to make washing practical.
Also your clothes shrink in hot water, specially cotton t-shirts. And the risk of color bleed increases with temperature too
I’m going to attack this from a chemist’s point of view. There’s a rule of thumb by Van ‘t Hoff that dates back to the… late 19th century that says, *roughly*, the rate of a chemical reaction increases by a factor of 2 for every 10C (=10K) of temperature you perform the reaction at.
Assuming the reaction here is “whatever the detergent does to make your clothes clean”, you can hope that raising the temperature from 40C (“rather gentle, use for colour”) to 60C (“definitely fine for white”) is going to work 4x as well.
More at https://en.wikipedia.org/wiki/Van_%27t_Hoff_equation
The temperature of water is a way of describing how much the tiny water molecules are “jiggling”. In cold water they are standing more still and in hot water they are shaking around.
Most chemical processes go faster with higher temperature because the random jiggling of the molecules can help them align themselves correctly and can propel the molecule past a molecular barrier. You might imagine sand poured into a sifter that is being held still or sand poured into a sifter that is being shaken.
With detergent, you are forming tiny bubbles that hold oils on the inside and water on the outside. The jiggling of the molecules can help the oils from the clothes find their way into the center of the detergent bubbles.
On the other hand, hot water may damage certain types of fabric and may remove the color molecules from the clothes. The water that is coming out of your plumbing is probably already warm enough to do a good job cleaning clothes with good detergent and agitation (stirring that the washing machine does) alone.
What range of temperature is cold water?
It might feel less “clean” to her — some stubborn stains (oil etc) won’t lift as easily.
However, there’s a lot of pressure (esp on new mums) to wash clothes at high temperatures; this kills any germs/bugs/mites in the clothing and is important for babies and bedsheets etc.
Side note, I only use cold water now, and very little detergent unless there’s serious dirt or grime on the clothes. If they smell, toss a small bit of white vinegar in there. My clothes, as a result, last 10x longer, and they smell perfectly neutral (if I use a scentless detergent).
It’s hard to prove, but I feel its saved me thousands of dollars over the last 6-7 years.
Really the only thing you need to be aware of is that the hot washings also help sterilise the machine, so if you only wash cold, you can get microbial growth inside that could cause smells or skin irritations.
Even if cold washing is good enough for the clothes, it’s not a bad idea to do 1-2 hot cycles per month or use some kind of machine cleaning products.
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