Sunday, April 10, 2011

The Science of Washing Nappies

by Amanda McCracken, with Jacqui Parncutt and Kirsten Randle.

With the advent of modern cloth nappies a new regime of eco-friendly laundering has come into being. No soaking, no bleach, no boiling water. Modern nappies don’t require all those things of the past! All sounds very well, but in many parts this has been taken to an extreme – gentle washing, cold water and minimal detergent. The result: smelly nappies that are deteriorating before they should.
As much as we want to believe that we can get away without chemicals or hot water, it goes against the laws of science and nature. Going against the laws of science in the laundry is like standing naked in the rain and expecting to get as clean as you would by scrubbing yourself with a soapy washcloth in a warm shower.
We must always remember that nappies are essentially our babies’ toilets for the first two years of their lives. We are not washing clothing which may have a bit of dirt or food marks, we are washing little toilets and trying to get them clean enough that our babies can wear their toilets, right next to their skin, over and over again.

Using science in the laundry.
There are four main factors to consider when trying to get your nappies clean.

1.Thermal Energy (water temperature)
2. Water Softness (mineral content of the water)
3. Mechanical Energy (agitation)
4. Chemical Energy (detergent)

These four factors work together to help reduce the surface tension of water which in turn allows it to get into the fibres of the nappies an clean them. If you decrease one factor other factors will need to increase to compensate for that loss. This explains why people in Adelaide with hard water will require more detergent than people in Melbourne, and why they have to scrub harder with a cake of soap in order to make bubbles.

How to wash nappies

Wash early, wash often. Like any laundering; nappies will be cleaner if they are washed soon after they become dirty. The urine has less chance to eat away at the fabric, the bacteria has less chance to breed, and any stains that may arise from soiling have less time to set. Most importantly, this is not the time to skimp on water.

1. Dry-pail. This is still a good idea from a practicality and safety point of view. A) No Heavy Lifting involved and B) No Drowning Risks to young infants. You’ll get a better result if you give your nappies a quick rinse under the tap before popping in the bucket.

2. Prerinse. This step should be done with cold water and no detergent. The aim of this step is to try to remove much of the urine and bacteria from the nappy - so we need less detergent to get the nappies clean in the next step.

3. The wash. This is where you need to contrate on getting the combination of water temperature, softness v hardness, mechanical energy and detergent right. Now while you might not have a lot of control over your water softness or hardness, you can control the three other factors. You don’t always need hot water, and it may damage other parts of your modern cloth nappies such as the elastic or plastic components, but you may need to hot wash occassionally. If you use cold water, you will need to compensate by using more detergent. So a balance is best. Warm water with an appropriate amount of detergent and a wash on the longest cycle.

So which detergent is best? We recommend a non-purfumed, enzyme free, optical whitening free, phosphate free concentrate or an ultra-concentrate. You want the best bang for your buck – the most bubbles for your scoop. As many babies can show reactions to detergents, you want the least amount of fillers – as small traces may remain on the fabric, even after a final rinse.

4. Final rinse. This is to remove as much of the detergent residue as possible – so as to reduce the risk of skin irritation of your little one’s behind.

5. Line Dry. The sun will provide you with lots of lovely UV rays that will kill bacteria and assist in sterilising your nappies. Great news for Queenslanders! Not such great news for southerners in winter, although many of us can make do.

If your nappies smell, it is likely you have a cleanliness problem, that is, you are not washing the urine and bacteria out of all the layers of your nappy. In this situation you need to work on lowering your surface tension of the water so that it will clean your nappies properly, by changing your thermal and/or chemical energies.

The extras

  •  Hot water – This has a lower surface tension than cold or warm water meaning that it gets into the fibres of the nappies and cleans them more easily as well as killing many bacteria. Hot water may decrease the lifespan of PUL and elastic but it does have the advantage over chemicals that it won’t leave a residue that could cause irritation to baby’s skin. Anti-bacterial rinses - These will help to sterilise the nappies and once more will help to lower the water surface tension – resulting in cleaner nappies. They are recommended after gastro, thrush, live vaccinations and a bad case of nappy rash. Also handy in winter if you aren’t getting enough UV rays from the sun to sterilise your nappies.
  •  Nappy Sanitisers – Like the anti-bacterial rinses – these use chemical energy to both kill bacteria and to lower water surfact tension. The active ingredient breaks down in water to a water softener and hydrogen peroxide – which will further break down to water and oxygen. Often cotain optical whiteners and enzymes which may cause rash. Rinse well.
  • Vinegar – can be used to lower the pH of the nappies caused by detergent residue.
  • Dryer - isn’t such a great idea because it deteriorates elastic and PUL in your modern nappies as well as using enormous amounts of electricity. If you do use it you will need to use it on a hot enough setting to prevent bacterial growth, since you are omitting the sterilising step that the sun performs.

Most of us who use modern cloth nappies do so because we want to reduce our footprint. We want to live eco-conscious lives, lower our impact on our environment. But this does not mean we can wish science away. Warm and hot water, detergent and chemical solutions need not be the enemies. They can help us get longer wear out of our nappies and make those years that we have little ones in nappies a pleasant, satisfying experience.

Amanda McCracken B.Com.

Amanda is a mother of four children six and under, all of whom have been cloth nappied. In 2007 she established Mandy Mac, a successful modern cloth nappy business which she runs from her home in Melbourne. See

Jacqui Parncutt B.Sc. (Hons)

Jacqui is a Melbourne based medical scientist. She is a keen modern cloth user with a soft spot for microbiology. She wanted to share her knowledge of bacterial management in the laundry, especially with regard to cloth nappies.

Kirsten Randle B.Sc., M.F.Sc.

Kirsten is a very busy RAAF wife and mother. She has a Bachelor of Science, Master of Forensic Science (Firearm Chemistry) and almost completed her PhD in Applied Chemistry (Forensic Science/Counter-terrorism) as well as being an avid fan of modern cloth.

Photos by Pamela Bradford and Debbie Treweek


  1. Great article and lots of excellent advice however I would suggest "not" using anti bacterial treatments as these have been linked with the rise in resistant bacteria, and will kill any good bacteria present. Adding bi carb soda or epsom salts will naturally soften your water, if your water is hard adding more detergent simply won't soften it. The bubbles are not the cleaning agent, they are merely foam from chemical reactions and if there are lots of bubbles present this actually indicates too much detergent is being used. Our skin is essentially a sponge and if you have residue of detergent on wet cloth on skin you can really cause some major irritation. So go easy on the detergents, go strong on the sun and yay to using re usable nappies :o)

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