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.

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

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.

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.

 

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.

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.