Thermal Death Point

What is thermal death point?

the temperature at which all organisms of a culture will be killed by heat either instantaneously or within an arbitrary brief finite period ~merriam webster

So that means how hot and how long you have to heat something to kill all the germs on it–to sterilise something. It’s worth knowing that for most things, that’s a really long time and you’re not gonna get there in the home. You can sanitise things and get stuff pretty clean and that’s good enough. Don’t kid yourself, though, about what you’re really getting out of various cleaning tools and routines.

Washing machine

We bought a really good washing machine (Miele) with a 72 and 90 degrees C wash, but it probably doesn’t do that in reality. Most washing machines don’t actually reach their stated temps or hold there for long enough to kill bacteria. So we combine the boil wash with a bleach soak or bleach additive (sodium percarbonate, any brand, never chlorine) to try to cover our bases. Every now and again I just buy a kilo bag from a commercial cleaning supplier off eBay for about £10 and mix a small amount in with our powder, Formil (from Lidl, £4.85 for 130 washes or 4p - I used to make my own washing powder but Formil is almost as cheap and works and doesn’t irritate the skin).

Steam cleaner

We use a steam mop (with pressure steam attachment) to sanitise our floors, but they can’t sterilise. It takes an autoclave about 20 minutes of continuous pressure to sterilise something! So be realistic about what can be done with a £30 hot water dispenser, lol! The microfibre heads, though, will mechanically remove (upcoming!) bacteria well.

Dishwasher

These actually work! If you can get one with a sanitising and drying cycle, or a “baby cycle” so much the better. Use the hottest wash on there. You can clean and sanitise all kinds of things in a dishwasher, but it probably won’t sterilise anything. Our dishwasher is over 20 years old so who knows, really, what is going on in there. :P

Note: People with normal lives can just put their dishcloth in the dishwasher, but you are better off washing it in your washing machine. You can also microwave it, but you do risk burning down your house so, you know, put a wash on.

Hot water and a cloth

Hot water and a cloth simply cannot kill germs in any meaningful way. If it was hot enough to kill bacteria it would scald you. In fact there’s no advantage even to washing your hands in hot water vs cold. The cloth is only useful for mechanical removal (scraping germs off a surface and throwing them away).


Some other things I’ve been asked about but don’t use myself:

Pressure Cooker

This is actually a very basic autoclave. If you ever find yourself properly in need of one for some extreme reason, then there’s a tip.

Baby bottle steriliser / Home brew steriliser

These are cheap commercial versions of autoclaves. If you’ve got a specific reason to need one, maybe it’s not a bad idea to buy one of these second hand on eBay or Netmums or similar. But remember there’s really not much good evidence that they are doing what you probably think they are doing.