The Temperature Question: The results! (Part 1)

Back in May last year, the Nappy Science Gang citizen scientists decided they wanted to know what the best temperature to wash cloth nappies was. Now, after many months designing experiments, measuring nappies and many, many loads of washing, the results are finally in!

The gang of cloth nappy users wanted find scientific answers to questions about cloth nappies, but had found that the science that was out there didn’t ask any of the questions that were relevant to them. So, the Nappy Science Gang set out to answer them – beginning with what washing agent is really best for cloth nappies. After many weeks of discussion about the experimental protocol, the group designed and carried out two experiments- the first to see how washing at different temperatures affected the lifetime of a nappy, and the second to see how clean the nappies got when washed at different temperatures. This blog is about the first part of this experiment, and the second is described here.

Pictures taken by volunteers at various points during their experiments.

The experiment: What we did

The plan was to wash sets of nappies 100 times (which we estimate about the number of times a nappy would be washed over a year’s use) at different temperatures, and see what shape they were in at the end.

We chose 30°C, 40°C, 60°C and 90°C as our test temperatures, so four sets of nappies were sent out to a group of volunteers – the temperature teams – received one box of nappies which was passed around between them until all 100 washes had been completed. A spare set of nappies was kept behind as a control so all the nappies could be compared at the end.

Each volunteer also tested the nappies were inspected for balding and discolouration then tested to nappies to see if their absorbency or elasticity had changed after they had finished their part of the washing. However, balding was not the only type of damage that occurred and this along with a bad description of what to do for the elasticity and absorbency experiments meant we decided that it would be best to repeat the experiments at the end. You can see the full protocol here, along with details of some other small modifications we had to make along the way.

However, the hard work and patience of all the volunteers meant the experiment was overwhelmingly a success and we found out lots of interesting things. A special congratulation to Team 60 who were the first team to complete all their washing, as well as to all the volunteers who did their 20 washes in less than a week!

The results: What we found

First off, what did the nappies look like? As you can see from the photos below, washing 100 times has clearly had some effect on the size and shape of the nappies.

Images of nappies washes at different temperatures. Left: Little Lamb bamboo fitted nappies, Middle: Alvababy cheapy pocket nappies, Right: Little Lambs pocket nappies. Top nappies are unwashed nappies, then nappies washed at 30, 40, and 60 degrees C with 90 degrees C at the bottom.

Size and shape

Now, let’s look a bit closer. To start, how did the nappies change in size after 100 washes? Well, looking at the graphs below for length and width change we can see that most of the nappies tested have shrunk compared to the unwashed version. The nappies typically shrunk more at higher temperatures, though this was not always a consistent trend some of the nappies expanded (and some of them seemingly expanded or shrunk depending on the temperature!). Notably, the supercheapy nappy expanded the most lengthways and shrunk the most widthways, while the miosolo and little lamb wrap changed least in size. Little lamb bamboo fitted was the only one to be affected like this for both length and width.

Lengthchange.jpg

Graph showing the change in length for variety of nappies washed at different temperatures. Note the bumgenius pocket for 60 degrees is missing.width change.jpg

Graph showing change in width for a variety of nappies washed at different temperatures. Note the bumgenius pocket for 60 degrees is missing.

However, we do know that for many of the nappies, the unwashed nappies vary in size quite significantly, and we compared the washed nappies to the control nappies rather than the same nappies before they were washed. It’s also worth noting that domestic washing machines don’t always get up to the temperature they are supposed to. All this means that more repeats for the experiment would have been a good idea.

Elasticity

As for the changes in the elasticity, the lack of repeats may also have affected the results as there is a large amount of variation in the results. As you can see from the two graphs below, all of the nappies seem to get more or less stretchy depending on the temperature. Though this is possible, a repeat of the experiment with more trials for each type of nappy would be needed to say this for certain.

elasticity

Graph to show change in elasticity across the back of the nappy (the part that stretches around the back of the child) for the different nappy types. Note the bumgenius pocket for 60 degrees is missing.

 

elasticityleg
Graph to show change in elasticity across the leg of the nappy (the part that stretches around the leg of the child) for the different nappy types. Note the bumgenius pocket for 60 degrees is missing.

Absorbency
Similarly to the elasticity experiments, the variability in the results is large enough that another experiment would be needed to show how temperature affects absorbency. Perhaps one thing we can say for certain though – the temperature certainly does seem to change the absorbency one way or the other.

absorbency.jpg

Graph of the change in absorbency for a variety of nappies washed at different temperatures. Note the bumgenius pocket for 60 degrees is missing.

Waterproofing

The preliminary tests on how waterproof the nappies remained (that is, the wraps and outer coatings rather than any of the absorbent parts!) showed that none of the nappies which were washed at 30, 40 and 60 degrees C leaked while there was some leakage for several of the nappies which had been washed at 90. In our tests, the Alvababy cheapie leaked at the seams while the Miosolo leaked all over, though a more detailed study would be needed to confirm this.

On closer inspection of the PUL waterproof coating of the nappies, the Alvababy cheapie and Miosolo also showed the most damage to their waterproof coating, though the waterproof coating can’t always be seen so this doesn’t necessarily mean there was no damage shown to the others. As we can see from the photos below, the laminated covering of the Alvababy cheapie has started to come away at 90 degrees. For the miosolo, at both 60 and 90 degrees C from just looking at the PUL there is no obvious damage. However, if you stretch them out across the width (so holding the sides and pulling) you can see little cracks lengthways down the nappy, on the 60 they are dispersed, 1-4 mm in size. At 90, these cracks occur across the nappy, and again these cracks are barley visible unless stretched.

Photos of the Alvababy cheapy washed at 90 degrees, showing some delamination. Left: closeup, right full nappy

Photos of the miosolo nappy washed at 60 degrees showing the damage to the waterproof coating only visible when the nappy was stretched. Left: unstretched, right: stretched

Photos of the miosolo nappy washed at 90 degrees showing damage not visable when unstretched. Left: unstretched, right: stretched, cracks open and clearly visisble.

 

Appearance

As for the rest of the appearance of the nappies, there is clearly a trend that the higher the temperature, the less good the nappies look , though the degree to which thedamage occurs depends on the nappy. The miosolo did the best at resisting staining and balding as well as staying fairly soft, while the little lamb bamboo fitted nappy varied the most in texture (as well as size).

Nappy Change in appearance
30 degrees C 40 degrees C 60 degrees C 90 degrees C
Terry Square

 

 

No staining

No fading

Very low balding

Slightly rougher

No staining

Faded label

Moderate balding

Slightly rougher

No staining

Faded label

High balding

Slightly rougher

No staining

Faded label

Very high balding

Quite high roughness

Junior Joy Cotton Prefold No staining

No fading

Very low balding

Very slightly rough

No staining

Faded label

Low balding

Slightly rough

No staining

Faded label

Low balding

Slightly rough

No staining

Faded label

Low balding

Moderately rough

Little Lamb Bamboo Fitted No staining

No fading

Very low balding

Very high roughness

No staining

No fading

Low balding

Very high roughness

No staining

No fading

High balding

Very high roughness

No staining

No fading

Very high balding

Very high roughness

Bamboozle Stretch Fitted No staining

No discolouration

Low velcro bobbling

Slightly rough

No staining

No discolouration

Low velcro bobbling

Moderately rough

No staining

No discolouration

Low velcro bobbling

Moderately rough

 

No staining

No discolouration

Moderate velcro bobbling

Moderately rough

BG Pocket

 

No staining

No discolouration

Very low velcro bobbling

Very low balding

Slightly rough

 

 

 

No staining

No discolouration

Very low velcro bobbling

Very low balding

Moderately rough

Nappy missing

 

No staining

Faded label

No discolouration

Low velcro bobbling

Low balding

Moderately rough

Little Lamb Pocket Nappy Faded label

Low balding

Very slightly rough

 

Faded label

Moderate balding

Slightly rough

Faded label

Moderate balding

Slightly rough

Faded label

High balding

Moderately rough

Alvababy Cheapy Pocket Velcro very slightly bobbled

Very low balding

Slightly rough

 

 

Velcro very slightly bobbled

Very low balding

Slightly rough

Velcro moderately bobbled

Very low balding

Slightly rough

Velcro highly bobbled

Very low balding

Slightly rough

Cheapie Pocket

 

Faded label

Moderate balding

Moderately rough

Faded label

Moderate balding

Moderately rough

Faded label

Moderate balding

Moderately rough

Faded label

Moderate balding

Moderately rough

Miosolo Velcro very low bobbling

Very low balding

Slightly rough

 

Velcro very low bobbling

Very low balding

Slightly rough

Velcro moderate bobbling

Very low balding

Slightly rough

Velcro moderate bobbling

Low balding

Slightly rough

Table to show changes in discolouration and staining for different nappies when washed 100 times at 30,40.60 and 90 degrees.

So, in summary:

  • Most of the nappies shrunk more the hotter the wash. The supercheapie pocket and the little lamb pocket shrunk the most
  • Damage (eg balding, discolouration) to the nappies increased the hotter the wash.The miosolo did the best at resisting staining and balding as well as staying fairly soft, while the little lamb bamboo fitted nappy varied the most in texture
  • PUL waterproof coating was fine at 30 and 40 degrees for all nappies. At 60 degrees the miosolo started to show some damage and at 90 degrees the miosolo nappy was very damaged, as was the Alvababy cheapie
  • More experimens needed to establish the relationship between temperature  and the absorbency and elasticity of the nappies.
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