Softness Testing: Quantifying a Subjective Impression
Scratchy and stiff diapers are not in high demand with consumers today. Instead, parents seek a comfortable, well-fitting product that is gentle on the skin to cradle their baby’s bottom. Adults living with incontinence want the same. As a disposable hygiene manufacturer, you try to deliver softness, but there’s a complication: Many factors go into creating an impression of softness. In addition, not everyone perceives softness in the same way.
Some haptic criteria can be measured in a lab; others depend on individuals and their cultural bias. (The term “haptic” refers to impressions received by the sense of touch, and the use of technology to test the same.) For example, Asian markets tend to equate softness with silky and shiny. In the U.S., on the other hand, cottony and matte finishes bolster the impression of softness. Factors that tend to be common across regional markets include:
- Fuzziness
- Drape/flexibility
- Lack of roughness
- Low hand friction
To fully capture and measure the experience of softness, we recommend a two-pronged approach using both analytical techniques and human sensory panels.
Analytical techniques for softness testing
Various methods can be used for evaluating specific haptic traits such as fabric stiffness and drapability. For example, stiffness can be tested using a plunger to push fabric through a hole in the surface on which the fabric is resting. The force needed is an indication of the fabric’s stiffness. Drape can be tested by centring a circular piece of fabric on a smaller round or spherical surface. An image can be taken from the top, showing fabric draping over the sides of the surface. Mathematical formulas can be used to determine drapability values, or visual comparisons can be made based on the size of the impression.
Tissue softness analysers (TSAs) can perform a variety of haptic tests associated with softness, such as smoothness, elasticity, compressability, and others. Haptic data can be fed into algorithms to provide statistical softness scores. These algorithms can be adjusted based on cultural perceptions regarding which aspects of softness are more or less important.
Human sensory panels for softness testing
Product softness can also be evaluated by product users or trained testers with a common set of criteria. Traits may be listed, along with a description and the preferred method of evaluating. For example, to measure hand friction, “Place the palm flat on the fabric; using the weight of the hand, move hand horizontally across the surface …” Panel participants may be asked to compare products, or to rate individual products on a scale, such as 1-5.
Challenges a sensory panel can face include:
- Repeatability
- Reproducibility
- Cultural/personal bias and sensitivity
- Vocabulary
- The lack of test method standardisation in the industry
If you’re investigating softness for your disposable hygiene products, talk to our experts. We can help you consider your options—from softer substrates to the right adhesives—to help you meet your goals.
Contact Bostik’s softness experts today to start the conversation.