The Conversation expresses some opinions about that …
They say towels should be washed in 65+ deg C water and that face washers should be replaced daily.
IMHO, such a high degree of anxiety about micro-organisms is not warranted, nor is the idea (promoted by the manufacturers of household cleaning chemicals) that we should coat every surface in our house – including the floor and inside of the toilet bowl – with chemicals that ‘kill 99.9% of germs’.
Such practices can actually be harmful, removing beneficial micro-organisms that would’ve competed with the dangerous ones, and in the long run just breeding up hard-to-kill versions of the bad ones.
Certainly, if your sheets, towel, or face cloth look grubby and/or smell a bit off before you’d normally replace them, do swap them for clean ones – but you don’t have to use hot water to get them clean.
Most modern laundry detergents actually work better in cold or warm water than in hot, because a lot of their work is done by enzymes that’ll be destroyed by hot water.
So said my mother and her mother before her. The wood fired boiler, later the electric boiler was fired up just for that purpose. It was assurance of sterilisation in the thinking of the day. Reality is with the soaps in use it was also convenient to maximise cleaning vs the more laborious and less practical use of wash boards - especially for larger items.
To note our front loader insists at times on running a hot wash cycle (70C). To help keep the internals and internal plumbing clean. Legionella do not survive at temperatures above 70C or at 65C for more than a few minutes. If it was still essential with modern day detergents to wash that hot would there would be a great many of us all dying from not using very hot/scalding water? Although if in a hospital standard autoclave steam sterilisation requires 121C.
Is there a need to qualify this point?
Laundry and cleaning products contain a variety of enzymes. They differ by purpose and brand. Is it certain that the colder the water the better they work, or is there an optimum temperature range? Some sources on line also suggest that the water needs to be very hot (70-80C) before it destroys enzymes.
To note Choice only tests laundry detergents at 20C. Choice previously also tested with warm water 40C. Does it make any difference, and other useful advice?
A perception is our choice of powder (front loader) works a little better at 30C.
The reason our washing machine manufacturer (Bosch) gives for the monthly (or so) hot-water wash is to prevent build-ups inside the machine and the pipes of anything that doesn’t get completely flushed out on each wash, and also to clear out any mould that might be taking hold in the intake and outlet pipes. You either run the machine’s cleaning cycle, empty, or make a point of doing at least one load at 60+ degrees each month or so.
About enzymes … apart from their ability to tackle cleaning the fabrics, they’re intended to produce satisfactory results at lower temperatures than detergent alone. So there’s generally not much point in washing at very high temperatures, because the enzymes probably won’t do any better job in hot water, so you’re unnecessarily using energy to heat the water.
I don’t have specific references, but many articles I’ve read also say that some of the enzymes in detergents don’t like heat, and may be less or not at all effective if the water’s too hot.
Many of the enzymes used are found in digestive systems. I guess those would probably like to be at around internal body temperature, so maybe 30-40 degrees C. That seems consistent with your observation that 30 deg seems to be optimal for cleaning performance with your choice of powder and your front-loader.
I wash in cold water, when the washing machine starts to get that musty smell I put a small amount of Ti tree oil in with the final rinse, doing this 3 or 4 times kills off the odour due to ti tree oils antiseptic properties.
Tea tree oil is anti-fungal as well as antiseptic, so – in the right proportions – it could get rid of mould in the machine. As does a hot wash or cleaning cycle as recommended by the washing machine manufacturer.
