Sunday 29 September 2019

Diaper Test Methodology

As I set out to review the best (and maybe worst) adult diapers on the market it seems prudent to establish some reasonable evaluation criteria. Diapers serve a single simple purpose, but providing greater absorbency doesn’t necessarily make a diaper better for practical use. In reality, the rate at which a diaper wicks away moisture, positioning of its padding and effectiveness of its leakguards under pressure can make or break a good diaper. Without good wicking, a quick void will pool around a single location and leak from the sides of the diaper regardless of its theoretical capacity, likewise in the case of poorly positioned padding. The material used in the backing is also important as leaks can happen with a flimsy backing or out of the side panels.

To provide a reasonable assessment of absorbency I’m dividing my absorbency tests into two categories: laboratory and “real world”. The laboratory test targets the theoretical capacity of each product, while the “real world” test aims to assess how the products will perform in a realistic use-case.

In addition to absorbency, products will be tested for their ability to hold up to the wear/tear of daily/nightly use and I will try to best assess how comfortable the product is and remains to be over time/usage. Moreover, I will run a series of tests to evaluate how discreetly each product can be worn and provide important product details like size/thickness to assist in the evaluation. I will aim to provide a good balance of textual and visual information to help readers assess which products will work best for their own purposes.

 Laboratory Absorbency Test

The laboratory absorbency test focuses on the absolute absorbency that each product can achieve in an ideal setting. Additionally, this test will gauge how effectively each product can retain moisture using a “press-out” test.

 Part 1: Capacity Test

In the capacity test a freshly opened diaper is pinned flat onto a flat waterproof surface and dyed salt water (0.9%) is added into the container in 250 ml (8.45 oz) increments of about every 10 minutes until the diaper begins to leak. Between tests a 2.5 kg (5.5 lbs) weight is placed over the center of the diaper where the liquid was added. After each round the inner surface of the diaper is dabbed with a paper towel to determine whether the surface is wet to the touch.

1.1 Capacity Test Setup and Equipment

The amount of water added to the point of leakage is recorded together with the weight of the wet diaper and its thickness when wet. The time needed to absorb each wetting is recorded to determine how effective the diaper is at wicking.

Evaluation criteria:
  • Total absorption volume will be measured
  • Time needed to absorb each wetting will be measured
  • Percentage of used vs unused padding will be recorded
  • Pattern of used padding will be recorded
  • Thickness when wet vs dry will be recorded
  • A surface dampness rating will be given based on how much liquid ends up on the paper towel in the test before failure (1 = very moist surface, 10 = a very dry surface)
  • A proportional rating of padding to absorbency will be calculated

Part 2: Press Out Test

During the press out test a flat glass bowl is placed over the diaper and it’s pressed until it no longer leaks. At this point the diaper is re-weighed and the change in weight is noted (this is the press out volume). Press out volume provides some insights into how likely a wet diaper is to leak when put under pressure (e.g. under the body weight of an individual who just sat down).

1.2 Press Out Test Example

Evaluation criteria:
  • The volume of press out liquid will be measured

“Real World” Absorbency Tests

The laboratory test gives a sense of how each diaper could perform in a lab but it doesn’t capture the many factors that lead to leaks in real-world usage (e.g. positioning vs padding distribution). Nor does it account for any discomfort that can arise out of produce usage (e.g. clamminess/skin irritation). The real world absorbency tests assess how the diaper might perform when actually used.

Part 1: Posture Tests

The posture tests assess diaper performance: standing, sitting, and lying down. The diaper is wet in each posture and any leakage is noted. At the point leakage occurs the diaper will be removed and weighed to compare against its dry weight. Comfort when wet and whether any skin irritation occurred will also be noted. The standing and sitting tests will be combined into a single test with the diaper first wet standing, if no leakage occurs then 5 minutes later it will be evaluated for leakage after sitting down.

2.1 Diaper Postures

Evaluation criteria:
  • The percentage of unused padding at the point of leakage will be recorded
  • The pattern of used padding will be recorded to identify likely sources of leaks
  • The volume of liquid at the point of leakage will be measured
  • A sitting/standing/lying rating will be given to account for harder-to-measure aspects of absorption (1 = leaks in a flash, 10 = holds its own)

Part 2: Daily Wear and Bedwetting

In this section the diaper is evaluated for how it could be expected to perform for daily wear and bedwetting. Notes will be taken of any leaks or sleep interference that might occur as a result of wearing for bedwetting; likewise for daytime usage. The condition of the diaper will also be noted (e.g. will the tapes hold through the day/night?).

Evaluation criteria:
  • Evaluation here is done purely on an experience/analytical basis; this section will include a write-up describing how the diaper could be expected to perform and other important notes (e.g. how frequently changes might be necessarily and whether it could be prone to leaks in unforeseen circumstances)

Wear & Tear Tests

In this set of tests the diaper will be assessed for fit, comfort, and durability. The goal here is to provide a sense of feel of the product and identify areas of potential difficulty or discomfort for those wearing or managing a patient as a caregiver.

Part 1: Fitting

A common concern in adult diaper usage centers on getting the proper fit. If applied incorrectly the diaper is likely to chafe the skin and may result in leaks (see “How To Properly Apply An Adult Diaper”). In some products a good fit is inherently easy due to the design, while in others it can be a struggle to get the appropriate fit. In this series of tests the diaper will be assessed for how easy it is to properly fit (and refasten if applicable). Notes will be taken on the fastening mechanism and how well it holds in place.

3.1 Example Diaper Fastener

3.2 Diaper Fitting Front/Side/Back

Evaluation criteria:
  • Ease-of-use ratings will be given (1 = difficult to apply, 10 = easy to apply)

Part 2: Comfort

Gauging the comfort of a diaper is perhaps the most subjective area of assessment. Diapers come in many shapes, with various materials and sizes and it’s important to distinguish the aspects that make one more comfortable than another.

To assess the diaper’s comfort, notes will be taken on its build and materials. It will be worn both dry and wet and evaluated for comfort under varying conditions. Any chafing or skin irritation will be noted.

3.3 Diaper Backsheet (left) and Topsheet (right)

Evaluation criteria:
  • A comfort rating will be given for the diaper in both a wet and dry state (1 = very uncomfortable, 10 = very comfortable)

Part 3: Durability

Building on the comfort tests the diaper will also be put through several tests to assess its durability. These tests will cover daytime and overnight usage. In the daytime test the diaper will be worn dry for an entire day (8~10 hours) under low-moderate levels of activity (sitting/standing/walking) and evaluated for deterioration. In the overnight test it will be worn overnight (~8 hours) for bed wetting and in the morning evaluated for deterioration

Evaluation criteria:
  • The proportion of deteriorated padding (e.g clumped or torn) will measured.
  • Any breakdown in the fastener mechanism will be noted.
  • A durability rating will be given (1 = falls apart quick, 10 = very durable)

3.4 Dry Diaper Deterioration Test Results Example (Topsheet/Backsheet)

To better gauge durability of the wet diaper an additional test will be performed shaking the wet diaper lightly until the padding begins to fall apart. This test will aim to assess how long the diaper can keep its form under stress (most will fail quickly).

Evaluation criteria:
  • The number of shakes made before the diaper padding loses its form will be recorded

3.5 Diaper Folding for Durability Test

Discretion Tests

Discretion is a key selling point for many adult incontinence products, but providing a high degree of product discretion often runs counter to providing good protection against leakage. In this set of tests the diaper will be evaluated with respect to several categories of discretion.

Part 1: Profile

In this set of tests the visual profile of the diaper is demonstrated under different outfits and measurements/diaperless photos are taken for comparison.

4.1 Front Profile Comparison Example
4.2 Side Profile Comparison Example
4.3 Back Profile Comparison Example

Evaluation criteria:
  • Measurements based on profile to assess how visible the diaper is under clothing and how far it extends above the pant waistline
  • A profile discretion rating will be given (1 = obvious, 10 = barely noticeable)

Part 2: Noise

In this set of tests the noise produced by the diaper is measured when standing/sitting in a quiet room with a loose outfit.

Evaluation criteria:
  • The sound produced by the diaper during a sit-stand test in a loose outfit is represented in waveform for demonstration (e.g. does it stand out relative to the ambient noise)
  • A noise rating will be given (1 = obvious, 10 = barely noticeable)

Part 3: Odor Reduction

In this set of tests the diaper is assessed for its ability to retain odors. Admittedly short of purchasing very expensive equipment this is a tough one to measure; therefore, the scoring here is experienced-based and rated on a simple scale.

Evaluation criteria:
  • An order reduction rating will be given (1 = prone to odors, 10 = can't smell a thing)

Product Details

In addition to putting each reviewed diaper through the aforementioned series of tests they will also be described with more technical details. The diaper and package it comes in will be shown and presented with complementary details (e.g. length, width, thickness) and additional details like cost-per-unit. This will be done in a standardized fashion to assist with product-to-product comparison.

Diaper Dimension and Padding Measurements

Measurements of the diaper and padding will refer to markers on the two figures below.

5.1 Total Diaper Dimensions (left), Diaper Padding Dimensions (right)

5.2 Measurement of Stacked Diapers

5.3 Used vs Unused Padding Pattern after the Lab Capacity Test

5.4 The Diaper Package Dimensions

5.5 Diaper Tape Dimensions

Product Styles

An example of the different absorbent product styles available is shown below.

5.6 Absorbent Product Styles

Diaper Features

Some key diaper features that will be referred to in these reviews are identified below.

5.7 Diaper Features


Backsheet (Outer Backing): The surface of the diaper facing outward (away from the body). This surface will be either plastic or non-woven (cloth-like). (see figure 5.7)

Topsheet (Inner Surface): The surface of the diaper facing inward (toward the body) that is in contact with the wearer's skin.

Front Waistband: A waistband (stretchable material) at the front of the diaper (as it relates to the wearer). Diapers that feature a front waistband might provide a better fit.

Rear Waistband: A waistband (stretchable material) at the back of the diaper (as it relates to the wearer). Diapers that feature a rear waistband might provide a better fit and some protection against leakage from the back when lying down.

Folded Thickness (dry): This is a measure of the thickness of a folded diaper; to better assess thickness this is calculated by stacking 3 diapers, compressing them with a book, measuring the thickness of the 3, then dividing by 3 to get the single diaper thickness. Thickness can reflect how absorbent the diaper is and may also help determine whether it will stand out under clothing. (see figure 5.2)

Folded Length: This is a measure of the length of the diaper (e.g. the longer dimension) when folded. This could give some indication on how it might fit in a backpack or purse.

Wetness Indicator: Typically a strip running along the length of the diaper under the backsheet that changes color or disappears when wet to indicate it's time for a change. (see figure 5.7)

Standing Inner Leak Guards (Inner Leg Cuffs): This waterproof layer runs as two parallel strips along the length of the diaper and will help contain leaks out of the side; it's also an essential feature for containment for those with bowel incontinence. (see figure 5.7)

Leg Gathers (Outer Leg Cuffs): Like the name implies these run between the legs of the wearer and assist with fit and containment by matching the contours of the wearers body. (see figure 5.7)

Refastenable Tabs: These often come in two forms: double tapes, where the top tap can be removed and refastened to the bottom once positioned and tapes that can be refastened to a specialized landing zone at the front of the diaper. Alternatively, in some cloth-backed diapers this is achieved with velcro strips (hook and loop fasteners).

Repositionable Tabs: In diapers with this feature the faster can be removed and repositioned in a completely different area if the first attempt to fasten failed. This is often accomplished by including a specialized landing zone at the front of the diaper or cloth-based hook and loop fastener. This can be a useful feature; however, if done poorly it can result in tapes easily coming undone.

Diaper Dimensions: This refers to the total outer surface dimensions of the diaper.
  1. bW: the width of the rear wing
  2. fW: the width of the front wing
  3. mW: the minimum width of the diaper between the front and rear wings
  4. L: the length of the diaper
(see the image to the left in figure 5.1)

Wing Shape: the shape of the wing (the wider part of the diaper at its front and/or rear). Typically this is rectangular, but some may be flat or curved.

Padding Dimensions: This refers to the area of coverage by the diaper's inner padding:

  1. bW: the width of the rear wing padding
  2. fW: the width of the front wing padding
  3. mW: the minimum width of the padding between the front and rear wings
  4. L: the length of the diaper padding
  5. bPW: the width of the rear wing padding not including the mid section
  6. bPH: the height (length) of the rear padding (may be averaged if the wing shape is non-rectangular)
  7. fPW: the width of the front wing padding not including the mid section
  8. fPH: the height (length) of the front padding (may be averaged if the wing shape is non-rectangular)
(see image to the right in figure 5.1)

Padding Wing Shape: the shape of the wing padding (the wider part of the padding at the front/rear). Typically this is rectangular or cured by may also be flat.

Outer Color: The color of the backsheet (often white but can vary)

Inner Color: The color of the inner lining of the diaper.

Booster Pad: An absorbent insert pad with a permeable backsheet that can be placed in a diaper to improve its absorbency.

Bed Pad: A square or rectangular shaped cutout of absorbent material that can be placed above a mattress or piece of furniture to protect them from leakage.

Padding to Absorbency Ratio: The total absorbance after press out in an absorbency test in proportion to the surface area of the diaper. The greater this number the more efficient the padding absorbency.

Used to Unused Padding Radio: The total surface area of padding that absorbed moisture after an absorbency test in proportion to the total surface area of the diaper's padding. This is calculated by outlining the used and unused padding then dividing the used surface area by the unused surface area to get a percentage. (see figure 5.3)

Advertised Absorbency: The level of absorbency and/or absolute volume the product is claimed to absorb as specified by the manufacturer. This can give some indication of what should be expected from a given product.

Package Dimensions: The length (L), width (W) and height (H) of the reviewed package as calculated if the front of the package were facing toward you. (see figure 5.4)

Count Per Bag: The number of diapers provided in the reviewed package.

Cost Per Unit: An approximate cost rating for the diaper in relation to alternatives available in the market. This uses simple dollar symbol rating as follows:

  • $: Cheap (below market average where commonly available)
  • $$: Average (similarly priced with commonly available alternatives)
  • $$$: Pricey (a premium product with a unit price above commonly available alternatives)
Product Style: Absorbent products come in different shapes and sizes, the product style is used to categorize each:

  • Tab-Style Brief: what people commonly think of when they hear the word diaper, this product is fastened into place and the sides come undone when it's ready to be removed.
  • Underwear: these products look and fit like regular underwear but have an absorbent layer to prevent leakage.
  • Pad Insert: this refers to an absorbent pad worn within regular underwear (often held in place by an adhesive on its backsheet).
(see figure 5.6)
Fragrance: Some products add a fragrance to counter diaper odors, others may inadvertently emit a fragrance due to the materials used. If the diaper emits a fragrance it will categorized by similar familiar odors.

Number of Tapes: For diapers that use tapes to fasten the wings around the wearer, this measure refers to the number of tapes per wing (not the total number of tapes).

Tape Spacing: For diapers with tapes this measures the distance between the taps, the number of measurements reflect the number of tapes used.
  • t1: the distance from the top of the wing to the first tape
  • t2: the distance from the top of the wing to the second tape
  • t3: the distance from the top of the wing to the third tape

(see the image to the right of figure 5.1)

Tape Dimensions: For diapers with tapes, the tape dimensions can be used with the number of tapes to get an idea of how much surface area is holding the diaper in place.

  • W: the width of the tape (direction of diaper's length, see figure 5.5)
  • L: the length of the tape (direction of diaper's width, see figure 5.5)

Available Sizes: In these reviews only a single size of each diaper is tested; this describes other sizes that can be found in the same product line if relevant.