How We Tested Disposable Diapers

How We Test
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Worst versus best performing diapers in our absorbency test shown side-by-side. The large green areas in the Walmart brand, Parent's Choice, on the left, indicate significant wetness in the layer closest to baby's skin. In comparison, the BAMBO, although much more expensive, was dramatically more effective.
Credit: BabyGearLab Staff
We reviewed 24 of the most popular and highest rated diapers, including 11 eco-friendly diapers, in a side-by-side comparison to determine which was the absolute best.

Hands on Testing
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A key part of our testing process is seeing how each diaper performs in day to day use. By combining hands-on testing with quantitative tests, we believe we can better rate relative performance of each product.
Credit: NGK
We tested each diaper in day-to-day normal use over a 3+ month test period, and made careful notes on each diaper's performance relative to its competitors. We found hands-on testing observations for absorbency correlated well with our lab test findings. For example, diapers that felt wet to the touch on the surface after a change, were the same diapers that scored poorly in our lab tests for absorption.

Fit and Leakage
To determine fit and leakage we relied on our observations from normal day to day diapering as well as our in-house leak and absorptions tests and Amazon user reviews. Since we can't ask an infant to report comfort, we carefully assessed any marks on the skin and determined if they were caused by the diaper and why. We also lined up each diaper to feel and investigate tab placement, leg and back elastic quality, as well as to rough them up a bit and determine construction. After spending some time comparing and getting to know each diaper we assigned a score for there leakage, fit, durability, and comfort.

Creating the Lab Tests
After our extensive hands-on testing, combined with researching other reviews and reading parent's opinions on diapers, we felt the number one performance consideration when buying a diaper was absorption. This was not a big surprise, since manufacturers tend to emphasize their diaper's absorbency in marketing the advertising. Absorption plays a key role in diaper performance because keeping baby's skin dry helps avoid diaper rash, as well as avoiding overall leaks. The other concerns were leaks, comfort, durability, and eco/health friendly. We then assigned each a % weighting value in our overall ratings.
  • Absorption 40%
  • Leaks 25%
  • Comfort 15%
  • Durability 5%
  • Health 10%
  • Eco-Friendly 5%

Every diaper was carefully reviewed and scored on this system to determine their rank and to select the winners.

Lab Testing Absorbency
While stating that absorption is the #1 performance factor is easy, actually testing for it in a fair and objective manner is another thing altogether. We found that making fair scores based on hands-on use testing with babies proved too imprecise; it is hard to determine fairly how much and often a child is urinating, and these variances made judging diaper performance solely from hands-on testing too subjective.

We also found that the easiest test, namely soaking the diaper completely and measuring the total weight of liquid absorbed, did not predict or correlate to the actual performance differences we observed in hands-on use (this type of test is also discredited by industry professionals, see Inspiration below). We believe that the reason a soaking test fails to predict real-world performance is that it ignores the importance of a diaper's ability to accept urine flow from a point of entry from the middle of the inner surface, and then redistribute the fluid throughout the diaper's inner core (and away from baby's skin). We found this to be the crucial factor that separated a great diaper from a good one.

We set out to create a diaper absorption test designed to simulate how effective the diaper is at absorbing a significant urination event into a diaper's inner core, and measure the amount of surface moisture left remaining next to baby's skin. We're not so much testing for the absolute maximum ability to absorb fluid like a sponge, as we are looking for a diaper that can absorb a large urine release into the inner core of the diaper, while keeping the surface area next to baby's skin as dry and comfortable as possible.

Umm… Can You Mix Up Another Batch of Mock Urine?
So, after experimenting with various approaches to testing absorbency, we eventually came up with the test as described below. First, we added salt and food dye to sterile filtered water to create a mock urine with salinity that matches baby urine. Then we used a medium sized syringe to distribute 100 ml of the fluid into the diaper, using a standardized entry location and flow rate that approximates actual urination. We choose 100 ml to simulate a heavy overnight urine event for a size 1 diaper.

To put the 100 ml in perspective, that would correspond to a heavy overnight wetting volume from a well hydrated 14 lbs baby, at the upper limit of the size 1 range, which is what we were after to put the diapers to task at stress-test levels. After slowly wetting the diaper with 100 ml, we waited one minute for the diaper to absorb and distribute before adding 30 lbs of weight evenly distributed over the diaper area. This process was then repeated for another one minute interval of rest and weighting. We believe this weighting and unweighting process is important to be realistic, since the diapers are designed to redistribute the urine and then [ideally] absorb/lock it into the core away from baby's skin. Baby's movements play a role in that redistribution process. The time and 30 lbs weight were used to simulate, in standardized and highly repeatable manner, the redistribution of fluid in the diaper's core that naturally occurs from baby's movements. At the end of this process, most diapers will have absorbed the 100 ml into their inner core, and the surface layer which sits next to baby's skin should ideally be mostly dry. However, we found that some diapers did not completely trap the fluid in the diaper core; some diapers leaked from the edges, exhibited spots where fluid pooled, or simply were wet to the touch across significant areas of the diaper's top layer.

To create a record of the surface wetness on the layer next to baby's skin, we placed a science-grade filter paper on the diaper with 5 lbs of weight on top for 1 minute. Any green-dyed mock-urine moisture at the surface layer was readily absorbed into the filter paper which created a visual record of how much mock-urine remained closed to baby's skin versus locked into the diaper's inner core. We've included comparison photos of each diapers' filter paper tests in our reviews to help document out findings. We found these absorbency tests predicted accurately, and with higher precision, the same performance differences we more subjectively observed in our hands-on testing with a baby in normal day-to-day use.
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The above image is an example of our absorbency test findings, comparing the most popular brands versus Award winners (in the middle row positions 2-4). The green dye indicates areas where mock urine was not absorbed effectively into the diaper's core, and remained on the top layer of the diaper exposed to baby's skin. Thus, the less green dye you see on the filter paper, the better the diaper's performance in this test.
Credit: BabyGearLab Staff


Inspiration
Our absorption lab tests were inspired in part by a 10 page white paper published by P. Hardy of Disposable Consultancy Service. Mr. Hardy is a consulting engineer who has invented various diaper testing machines and is familiar with the details of diaper manufacturing and design from years of industry experience. Mr. Hardy points out that the most typical test, namely soaking the diaper to determine it's maximum absorbency, does little to predict the actual characteristics parent's cite as most important in focus group panels. His white paper outlines more sophisticated testing methods that more closely predict actual field performance. Mr. Hardy's white paper can be found here:
http://www.disposablesman.com/ArticleTesting%20240309.pdf

Here's a relevant quote on testing diapers from Mr. Hardy's white paper:
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Credit: Disposable Consultancy Service

What's In Those Diapers Anyway?
We relied on manufacturer's claims to determine the most "green" diaper meaning baby and earth friendly. This is an intense debate with many reporting no disposable can be green, thereby advocating only cloth diapering. Nevertheless, we assigned values based on our perceptions, manufacturers claims, and research.
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Most of the eco-friendly diapers we tested did exceptionally well in absorbency. We were pleasantly surprised when our lab testing debunked the myth that earth-minded disposables are less effective at containing moisture than more traditionally manufactured brands.
Credit: BabyGearLab Staff
We purposefully did not try to determine disposables versus cloth diapers. We intentionally kept the reviews separate, although we do use the same scoring system and absorption testing processes for both.

Some metrics were hard to determine given the lack of transparency on the part of many manufacturers. For instance, one of the factors we had concerns about was the use of dyes. Originally we took the diaper product packages and website claims at their word, and if a diaper claimed it was dye-free we gave it points for health. However, upon further examination, we discovered that being dye free was strangely subjective. With manufacturers using different words like dye, colorant, pigments, and inks, to describe their diapers composition, and no real one definition of these terms, it left us with an inability to compare the product accurately or even the ability to determine what the diapers were made of. In the end, we decided to report what the companies claimed for this, but not to give points for being dye free or using a different component that wasn't called a dye. It was just too difficult to tell which diaper contained what, and how that particular item was different from what other diapers contained. We suggest you proceed with caution concerning this aspect of health related concerns. Less is more, and we'd like them all to use less and we encourage manufacturers to be transparent going forward so parents can make educated decisions based on similar data.

No Bias
None of the diapers were given advantages or preferences in our tests. We pride ourselves on simply reporting our findings in an accurate and objective manner without bias. Some parts of our testing were inherently subjective, such as fit and comfort. However, when combined with the diaper's absorbency performance, it did directly link to leaks. In the end, we simply wanted to report what we saw in our tests, supported with facts from our research and experience.

Good luck with diapering and may potty training come sooner rather than later!

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