Washing at 60 degrees takes us 2 hours; washing at 30 degrees takes 10 minutes less. Logical, if you look at the heating time of the water. But shouldn’t you wash longer at 30 degrees?
There has been scientific writing about literally everything. Similarly on ‘The impact of washing cycle time, temperature and detergent formulation on the hygienic effectiveness of household clothes washing’ (Journal of Applied Microbiology2014).
At lower temperatures, a longer washing cycle is generally required to get the laundry equally clean, this article concludes. But the detergent used also matters. Detergents with ‘active oxygen bleach’ also get laundry clean quickly at lower temperatures, according to Applied Environmental Microbiology (2021), but it often contains chlorine: not very environmentally friendly.
An optimal balance
We ask machine manufacturer Miele. “The effectiveness of washing is determined by the so-called Circle of Sinner,” says spokesperson Maarten Bos. “It includes four factors: temperature, time, chemistry (i.e. detergent) and movement. A clean washing result requires an optimal balance between these factors. If you adjust one of them, it can affect the washing result.”
But how exactly does that work out? “It depends, among other things, on the washing program, the technology, the heating element, the detergent, etc..” In any case, eco programs (programs that use less energy and water) often take longer than regular washing programs. Compare it to driving 100 on the highway instead of 130, says Bos: “Then you drive a lot more economically, but you also arrive at your final destination. It just takes a little longer.”
But what about the non-eco programs, which last shorter at lower temperatures? “Every manufacturer has its own way of balancing those four factors,” says Olivier Bos of Electrolux/AEG. “We use different technologies to compensate for lower temperatures. For example, mixing the water with the detergent before it reaches the clothes. And an innovative relief pattern in the drum, which ensures optimal water distribution with as little stress as possible on the clothing fibers.”
Too short or too long?
Okay, but that all works at all temperatures. Why wash for a shorter time at a lower temperature? This is partly due to the warm-up time. Bos: “With the same program, in the same machine, heating up to 60 degrees takes about 20 minutes longer than heating up to 30 degrees.” But then you actually wash the 60-degree wash for too long. Because while it is heating up, the machine also washes the clothes for a while at 30, 40 and 50 degrees. Or was the normal 30 degree wash too short? No, says Bos, neither: “If the laundry is moderately soiled, you really don’t need a higher temperature. You choose the temperature partly depending on the degree of dirt.”
This is also what his namesake Bos van Miele says: “It depends on what you wash. A perfectly clean washing result is always our starting point.” Nowadays this works even better with a digital washing assistant and automatic detergent dosing, he adds. This made it easier and more economical.
And what does science say? More microorganisms survive at 30 degrees than at 60 degrees, all else being equal, he says Applied Microbiology simply. But as for pathogens, such as Staphylococcusit doesn’t matter, said The Journal of Infectious Diseases.