The big results reveal

Saturday 6th February was a big day for Nappy Science Gang – we had the big reveal of our experiment results at the Science Museum in London and the Shirley Technology labs in Manchester. We exchanged results (and excitement – ‘about to take a solo trip to an island resort level of excitement’, no less) on the chat site live. It lasted for almost four hours, and this is how it went:

Effects of wash temperature on the life of a nappy

Laura: I’ve just posted a photo (see below) showing changes in a few of the nappies after washing at different temperatures. Essentially, results were variable, but in some cases there was progressive shrinking with increasing temperature, and elasticity of leg and back elastic was altered.

NSG temp test nappy comparisons

A slide from the results presentation. Nappies at the top of  of each image are controls (never washed). Those below are, in order, those that have been washed 100 times at 30, 40 , 60 and 90 degrees C.

Chantelle: Any difference in perceived softness?
Laura: Yes! The controls are all lovely and soft and fluffy, the washed ones are definitely different.
Chantelle: Are all still at a functioning level of elasticity after the washes? Or was it completely relaxed in some? Did PUL have any damage as temperature increased?
Jemma: At which temperature did you see the most damage? Would you say there is a marked difference between the elastics on the 40 degree and 60 degree washes?
Dani: Did someone from Little Lambs have a response as to the longevity of their product?
Laura: The degree of change varies, Miosolos stayed fairly soft, Little Lamb bamboo fitteds for example changed hugely in size and texture (shown in the photo). 90 degrees definitely produced most shrinkage.
(At this point we explained that as the temperature washing experiments had only finished a few days before, we’d only really had chance to collect the data and not to analyse it in any detail but we will be posting summaries. No companies had seen the results at this stage.)
Chantelle: It looks like the largest change happens just from washing them at all, and then smaller changes with temperature. Even 30 makes a significant change.
Kate: Not much size change difference between 90 degrees and other temperatures. Those results are a bit varied but it must have been tricky to measure. Things not generally shrivelling up and drying though.
Hannah: Just checked the photo. Wow!
Kate: We should have also washed some thread somehow. We always forget about it, but sewing thread shrinks, almost always more than the fabric. If you saw leaking at seams, pulling of needle holes by shrunk thread could be a likely suspect.


As some background information to this section, details of how nappies were chosen for this experiment can be found here (written by Jenny McIntosh). In the discussion below, the Little Lambs nappy (‘sample D’)  which produced the ‘exoskeleton’ result came from a very hard water area in South Oxfordshire. It had been used, wiht two bamboo boosters, a fleece liner and Little Lamb PUL wrap, as one of six night-time nappies in rotation on one child who slept between 6:30 pm and 8 am and was given a coconut oil rub down each night and occasional application of Sudocrem. It was used for 9 months between January and September 2015, when it was retired as the velcro no longer fastened, and washed in a year old Indesit washing machine with 30 ml of Daz (about 1/6 of the dosage instructions for hard water and heavy soiling!) with an equal measure of Vanish Oxi Action (the nappy owner has noted that she recently switched to using two scoops Daz, one scoop Vanish and a water softener which has made an improvement. She also reported that her cotton prefolds have been used on two children and have held up really well compared to the bamboo ones which have only been used on one child).

Laura: Those of you at Shirley Tech, could you post some of what you’ve found for us please?
Grace: We are just having the presentation now.
Kirstine: We’re just having our presentation, but it is interesting that you mention 90 oC because we’ll have something to add soon…Here’s an interesting fact already from our meeting: Bamboo is not legally the correct name for Bamboo nappies and has no legal basis in this country. It is viscose, i.e. made via quite a toxic process.
Jemma: I read that about bamboo/viscose before and wondered how nappy manufacturers got away with selling them as ‘all natural’ etc.
Mark: In December last year US federal trade commission took action against 4 US national retailers for calling viscose / rayon product as made of bamboo and imposed civil penalties of $ 1.3 million against them.
Chantelle: Yes things should be labelled as ‘bamboo viscose’ but I think there is another way to manufacture bamboo fabric which is less toxic but it’s not as common. I don’t know of any manufacturers for diapers that use the other method. Jemma I think it’s because people don’t know what viscose is, so even if it’s called bamboo viscose they just see bamboo.
Kirstine: Apparently even using the term Bamboo viscose still has no legal basis regardless of the process and that environmentally friendly process is not used for nappies as the product is very rough.
Dani: Possibly because viscose can be made from Soy, Bamboo and other plants ….
Rebecca: The nappies sent to Manchester had lots of bacteria on but they cut one in half and washed one half at 90, this had 0 bacteria. High bioburden creates a hydrophobic biofilm which repeals liquid and so leads to the nappy losing absorbancy.
Mark: 5 nappies were submitted, only samples D and B were tested.
Kate: What were nappies D and B?
Mark: D was a mislabelled viscose though stated bamboo, wash details from submission: half dose bio and Vanish.
Mark: Nappy sample B was Polyester, a Totsbots V3.
Genevieve: So, does that mean repelling can happen because the nappies are still full of poo?
Rebecca: This isn’t surface poo. This is nano poo.
Kirstine: We’re just discussing that and I think the answer is no – it is the poo below the surface that is causing the problems.
Mark: Kirstine, a question for Ian in Manchester. Which one of his laboratory detergents did he use for his 90 wash?
Grace: Mark they used ECE detergernt which is laboraroy standard no brightners or antibac.
Mark: Thanks, Dani also used ECE A for her temperature work.
Grace: To note. It is live bacteria which is creating the biofilm at nano level. Dead bacteria may be present within the nappy but will not be causing the biofilm.
Chantelle: What do you mean at nano level? bacteria is microscopic not nanoscale
Rebecca: Apologies, the nano was not meant literally, yes microscopic level.
Rebecca: So in essence, all you need to do a stripwash is to wash at 90.
Chantelle: But mineral build up was not measured, correct? Because washing at 90 is not going to help with that.
Rebecca: Build up wasn’t measured but we have discussed follow up experiments. Final result: ash content of polyester is low, almost as low as the new nappy. “Bamboo” nappy was over 20%, the highest the technician had ever seen. When washed at 90 this reduced to 6.6%. rebecca-long But this depends on how often the nappy is washed as the ash comes from the a reaction build up.
Chantelle: What is the relevance of ash content?
Rebecca: The ash is what is left after burning. Not ash in the nappy. It is a measure of inorganic content.
Mark: Ash – after solvent extraction, you put the sample in a crucible in a muffle furnace at 600 C for 16 hours.Chantelle: So what exactly does a higher ash content indicate?
Rebecca: High ash content is caused by the presence of phosphate in detergents reacting with calcium salts in water to form a hydroxylated calcium phosphate. This is better known as hydroxyl apatite – and is an insoluble inorganic residue. This forms an ‘exoskeleton’ on the nappy fibres which repels liquids and so leads to the nappy losing absorbency.
Chantelle: Rebecca so bamboo having high ash content indicates a build up of detergent? And a 90 wash remedied that.
Rebecca: Not a build up of detergent. It is a build up of a compound created by a reaction between detergent and calcium in water.
Chantelle: Ok gotcha. So if the water was adequately softened, is it safe to say that this build up would be less?
Rebecca: Yes.
Chantelle: Are phosphates not banned in detergents? I thought nearly all detergents are now phosphate free.
Rebecca: Certain chemicals are banned but there are still phosphates in detergents. Apparently they are using less phosphates but they are still there.
Chantelle: Do detergents have to list phosphate as an ingredient?
Rebecca: Not sure if they have to list phosphate, no experts here.
Chantelle: Found this: In a nutshell, under the Regulation any household detergents shall not be placed on the EU market if the total phosphorus content is 0.5 grams per main washing cycle (consumer laundry detergents) and 0.3 grams per standard dosage (consumer automatic dishwasher detergents). The extension of the restrictions to dishwasher detergents followed an initiative by the European Parliament. The restrictions will apply for consumer laundry detergents as from 30 June 2013. So max is 0.5 grams per wash. Seems very low. Are we 100% certain that it’s the phosphates causing this issue? Is there a possibility it could be something else?
Rebecca: We are certain that the phosphates are the problem. 0.5 g is small but enough, it is the build up over number of washes that causes it.
Grace: The more you wash the higher the amount of reaction therefore the higher the deposit level.
Sarah: Are there also phosphates in water?
Dani: It is possible that EU regs are being disregarded. Possibly using 0.5 phosphates as well as other phosphate compounds.
Jemma: I may have missed this, but is there anything that can be added to the wash to cancel out the phosphate, or slow down the chemical reaction so stop or reduce the build up?
Mark: In large parts of the country orthophosphate is added to water supplies as plumbosolvency control.
Jemma: Mark, plumbosolvency control??
Mark: Prevent lead pick up from pipes and fitting.
Sarah: Mark and could that also be leading to this build up seen or is it a different form of phosphate?
Mark: Phosphate in water supplies is generally low that is why it is added.
Jemma: I’m concerned that there are so many things added to our ‘safe’ drinking water, but that’s a whole new topic.
Chantelle: Wow really interesting! And also leading to evidence showing that minerals can play a big part. I really hope we can do some mineral experiments.
Chantelle: Jemma I believe that properly softening your water with something like Calgon can help. It makes me think this is a better solution than just increasing the dose of detergent, because if you increase the detergent you also increase the phosphate.
Rebecca: We need to see the reaction temperature for the calcium phosphate water. It might be that it reacts prior to entering the wash or the heat from the wash starts the reaction. We need samples of water at cold fill point.
Chantelle: But if 90 removes this build up rather than adds to it maybe we can draw some conclusion from that. Detergents were at 40 from the write up.
Jemma: If you were to go with no wash additives, and had moderately hard water, how frequently would a 90 degree strip wash be necessary, based on the build up that was evidenced?
Mark It was a shame that you were unable to do an ash on Nappy sample G as according to the supplied data detergent was not used.
Nik: So it looks like those who were insistent that detergent can “build up” were right, to a certain extent! If the phosphates in the detergent are creating the compound that causes the problem, cutting down the amount of detergent would help fix it. Also, if this buildup is causing my problem, it looks like I can fix it with a 90 degree wash, but this will probably also make them leak, so they’ll just be useless in a different way.
Jemma: I think if you reduce the amount of detergent Nik then not as much soil is lifted, so I think it’s a balance.
Chantelle: Nik some people in Denmark wash regularly on 90. I think doing it once in a while isn’t going to kill them unless they are already showing signs of breaking down. I think this is pointing to using water softener like Calgon to minimize detergent if you have hard water.
Nik: Yes, I think this balancing act between too much detergent = buildup and too little = smells sums up the disagreements about how to wash nappies on most places I’ve seen! Interesting that we now have data to say that both sides are right.
Chantelle: Mark wasn’t the one they tested that had the large amount of build up using only half dose of detergent?
Mark: Yes and Vanish.
Nik: So many nappies “in need of strip washing” are not “dirty”, therefore? Just suffering from buildup?
Chantelle: Nik no there were still tons of bacteria on them too.
Nik: Why? Is there any connection between this dirt and the build up?
Kate: Would I be right in saying you’d struggle to clean them if they’re not absorbent too?
Mark: Hydroxy apatitle build up is common on materials of cellulosic origin but less likely on other materials. Build up was reduced to 6% and all bioburden gone with 90 degree wash.
Kate: It’s like the nappy fibres have become SUPER-exposed to too much phosphate they develop EXOSKELETA and become INVULNERABLE to weakling wee.
Nik: So how would we fix build up without the 90 deg wash? As it also looks like washing PUL at 90 is a pretty bad idea.
Chantelle: Mark is bioburden live bacteria or all ‘evidence’ of bacteria live or dead?
Mark: Bioburden 1 g of sample shaken in 100ml saline then 1 ml plated
Chantelle: Mark, plated = live then?
Mark: Yes.
Chantelle: OK, so we still can’t say from any of these results that bacteria isn’t present. Just that it isn’t necessarily alive
Kate: No phosphate declared in Vanish Oxi Action ingredients on Tesco website: >30% Oxygen-Based Bleaching Agent, <5%: Anionic Surfactants, Non-Ionic Surfactants, Zeolite, Enzyme, Perfume”. Right, so where do phosphates come from? No phosphates in Ecover powder, but 15-30% oxi bleach which seems to be in the high range from the ones I’ve looked at. Similar amount to what you find in sanitisers. Could be the detergent of choice for nappies. Method liquid is also phosphate free but lacks the bleach. The ones containing bleach did much better on the bacteria. Mark told us before how the peracetic acid which MioFresh claim as their antibacterial is produced from oxygen based bleach and the bleach activator TAED (TAED being the activator ubiquitously used in Europe, and bleach activators having been used commonly for a long time as they allow the bleach to work from very low temperatures). So I’m thinking your best powder for washing nappies has a good dose of bleach and no phosphates. Although if we get phosphates in the water supply that may be pointless.
Nik: Are the phosphates in the water in similar quantities to the detergent?
Kate: No idea…So interesting that microfibre polyester gets cleaner even than single layer cotton, in terms of live bacteria.
Dani: There are more phosphates in hard water apparently and its added to stop lead leaching into water so I imagine older cities and towns have more.
Kate: I wonder if from our early survey of washing styles, more people with hard water had nappies in need of strip washing.


How wash temperature and detergent affect bacterial presence on nappies

Dani: Here are results from Temperature. And here are results for Detergent . I suggest reading temperature ones first as they have an explanation of how things are done in layman’s terms.
Chantelle: Just to be clear is this live bacteria?
Dani: Yes viable bacteria only.
Chantelle: Can you explain the labels a bit? what is x4? And new vs old.
Dani: In the Temp results there is sheets across the bottom which have charts to easier understand it. x4 in the results means four layers. Like a booster. We wanted to see whether layering the fabric caused bacteria to be retained. New vs old is new vs old fabric. I used old battered nappy library ones versus brand new ones.
Chantelle: Were you able to test the temperature to see that it was actually reaching the specific temperatures?
Genevieve: I’m just on Chart #1 right now… am I right getting the impression that we’re better off with either 30C or 90C???
Dani: ‘From the data thats what it seems at the minute…. however take these results with a pinch of salt. They have not been statistically analysed yet, I am waiting on a colleage to run some H tests so we can say with 95% accuracy.
Chantelle: Interesting that 60 didn’t make a huge difference here whereas in my machine it nearly wiped the bacteria out!
Dani: Chantelle I am thinking that some null results marred it (ie, the swabs werent done properly or the bacteria died from a low temperature in the post office). But also we need to consider that some machines don’t reach the temperatures specified. If you go on Total2 chart you will see there is only around 200 CFU between 30, 60 and 90 Deg
Mark: Dani in your detergent tests, are the detergents A to G listed in the same named order?
Dani: Mark I still don’t know which detergent is which, it wasn’t revealed to me 😉 now I know which detergent is which I can compare other factors. I will compare bleaching agents, phospahte levels etc. And add that to the list of things that need statistic testing.
Chantelle: Dani were the tests done with detergent or just temperature? Am in the protocol now trying to answer some of my own questions, but don’t see that info.
Dani: The Word document is for Detergent. The Excel is for Temperature. I haven’t included the protocol for the Temperature as I was just going to talk through it (we were supposed to have a live Skype chat with Dani, but for technical reasons we had to switch to talking her to by text on the chat site).
Chantelle: Was it just a single layer of fabric or a whole nappy that was being washed? Trying to get a mental picture. Interesting that old fabric seemed to have more bacteria overall. Also PUL and Fleece having lower counts– I also got these results. And that bamboo didn’t have any less bacteria than cotton (even though it is touted as being ‘naturally antibacterial’).
Dani: Yes unfortunately I didn’t think to mark the nappies so I could see if they were harbouring a constant colony.
Genevieve: Bamboo seems to hold onto more bacteria. Does a fleece liner protect baby in a way that putting them straight onto a cotton or bamboo nappy would not? Can we infer that from the results? I always heard cotton was easier to clean, this is really interesting to see. Will be great to see what the statistical analysis says.
Dani: Possibly, it seems that the fleece would repel. But I personally think it has lower count as it is drier. It was almost dry when it came out the wash.
Chantelle: Dani so are you saying that drying is killing the bacteria or that it’s not transferring well to the culture plate since it is more dry than the others?
Dani: Chantelle I think both. Bacteria need moisture to survive so a dry fabric will kill them. Also as it repels the water we can assume that some (not all) colonies that have not established a biofilm would be washed out with the water as a vector. The swabs were moistened with saline so theoretically it should be easy to get a sample but probably did cause problems in practice.
Chantelle: For the temperature experiments, which washing powder (if any) was used? Was it one of the ones that was also tested in the detergent experiments? And in detergent experiments which temperature was used?
Dani: For Temperature I used ECE and the Detergent ones were the ones listed on the write up.
Chantelle: Interesting. Well it looks like non bio at the recommended dosage works just as well as bio for the most part. Liquid tabs, eco eggs and soap nuts did the worst and seems like they grew the most gram+ bacteria too. I am drawing that from your raw data. I sorted it to look at just the plates that did grow something. (Chantelle and Dani then went on to discuss a result that showed no colonies, which they continued via email).
Kate: What was the wash temperature for the detergent test? And was it box recommended dose used in each case?
Dani: It was 40* for detergent test and box recommended dose
Kate: Did each tester use all the detergents, or each tester did one each?
Dani: It depends. Most people did 3 random detergents but we had quite a few that fell off the radar, didn’t complete or disappeared in post.
Jemma: I was surprised by how many seemed to disappear in the post, not sure if it may have been exacerbated by the extra post due to it being the run up to Christmas.
Kate: So it’s looking like bleaching agent is good for killing bacteria. Which makes sense.
Mark: Dani The Shirley Technologies strip wash with ECE at 90 had a reduction in CFU from 3400 to 0 five replicates wrt to bioburden.
Dani: Mark I can only assume that is because this was done in domestic machine which is not as effective.
Mark: They used a domestic machine for that test not a standard one. (Mark listed technical details of the test).
Dani: I have no idea then. I did a sterilise wash between each test at 90 with machine cleaner. I thought it was strange that there were so many bacteria at 90. It might be worth testing what temperature it reaches, as it’s an economy machine.
Mark: A good idea to temperature check.
Kate: Never using a multilayer bamboo thing. Euch.
Nik: Just bought a pile of them SECOND HAND! Ha. I will definitely be doing the odd 90 deg wash on them!
Jemma: Kate another variable, there are so many, I’m sure the brands all have different types of elastic too, as I would expect if is is more relaxed the leakage will be greater.
Kate: Jemma, how was that leakage tested though? The absorbency tests were done with pouring liquid rather than on babies, so fit wouldn’t be a thing?
Chantelle: Dani I had a ton of bacteria on towels washed at 90 with no detergent if you recall. My machine tested to get into the 70-80s I think. Did you do a control to show how much bacteria there was before washing?
Jemma: I read a post someone shared, I think it was in Nappy Go Lucky or Go Real the other day, or maybe even this group, anyway it tested the temperature of around 8 brands on a 60 degree wash, over half barely reached temperatures in the 40s.
Kate: There is a bit of a spike on total bacteria on old items washed at 40. Wonder why? Bit like body temperature?
Dani: I wondered if the old ones had a ‘colony’ of bacteria that they carried over. Its possible that the 40 wash was low enough not to reduce the bacteria.
Kate: Dani, the bioburden found. Is it big? I’ve no idea what average would be.
Dani: Kate the cotton is very damp when it comes out the wash. I imagine when dry they might have similar levels. Also the synthetic fibres provide less holding for bacteria.
Kate: Just because the synthetic doesn’t really absorb, Dani? From what I understand the liquid more sits in between the fibres? Do bacteria evaporate off with water as fabric dries? That’s a really interesting thing actually. The wetter it is the more bioburden you’re likely to absorb. Bamboo > cotton > microfibre > wool > fleece > PUL I think is roughly the order most would agree on in terms of absorbency, which is almost exactly the same order as the bacterial load, which might make that a bit of a red herring. There is a definite spike when there are multiple layers though I think.
Dani: I have been desperately searching for info on average bioactivity but coming up a bit spare. For an item that comes into contact with a butt its pretty good. Under 500 non pathogenic is generally acceptable for human contact. They dont evaporate but they do die.
Kate: So there would be some impact as dead bacteria provide food for live bacteria.
Dani: Some pathogenic bacteria form endospores so they can survive when the fabric is dry. Dead bactetia dont provide much food as they generally run till they exhaust of all material
Kate: I bet people commonly use hard-to-dry nappies before they are fully dry too, as they take an age. So maybe it is a problem.
Nik: Should we be all rushing out to buy MioFresh? I’d be interested to see how it performed on its own!
Kate: I think it looks like the Mio Fresh is providing a boost of oxygen based bleaching agent. You can find similar levels in Oxi Action and non-branded copies and in Napisan. And you can find powders with similar levels.
Dani: We can put some miofresh on some assay disks and drop them on a plate of agar and see how strong an antibacterial effect it has outside the wash.
Kate: Wow is that how bacteria works? I think we’d need it to dissolve so those ingredients react together. It would be interesting to look at others with a similar bleach content.
Dani: Bacteria can survive 24 houra dry usually so even waiting a day after those pain-in-the-butt all one ones to dry, you could still be putting live bacteria on your child. Now imagine if they have nappy rash? Bang infection.
Dani: We could certainly test a few cleaning agents for their antibacterial effect, the way I described is how they test antibiotics.
Nik: So we should ideally wait more than 24 hours after drying our nappies before using them? Or does it look like using sufficient oxygen based bleach makes that unnecessary?
Sarah: This is so interesting, would be interesting to see how much bacteria remains on semi-dry nappies.
Dani: If a child has nappy rash I would either line dry, wait a day or dry on the radiator / dryer
Kate: Depends on the nappy type maybe Nik. Multi layer bamboo is going to take ages to dry. Fleece comes out nearly dry. The former showed much more live bacteria than the latter. Sarah maybe we could wash dirty nappies and cut them open and swab after certain amounts of time.
Nik: Yes, my bamboo Little Lambs come out of my tumble dryer slightly damp.
Sarah: Kate, good idea, and of different types of fabric and layering.

Chantelle: Interesting day, looking forward to getting some more conclusions out of it!
Jemma: Thanks everybody for all your help and feedback today.

2 thoughts on “The big results reveal

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