Expert's Opinion

Not all Wetness Indicators are created equal

By Mack Wei, nonwovens sales and technical manager | April 19, 2012

HB Fuller's Wei discusses quality in wetness indicators.

A good wetness indicator is both a useful and differentiating feature for baby diapers and adult incontinence products. Because they change color in the presence of moisture, wetness indicators help to reduce waste by ensuring caretakers make a change only when it is necessary. On the other hand, not all wetness indicators are created equal.
Quality wetness indicators will offer the following five features:
Fast and distinct color change: The color change after an insult, or the wetting of a diaper or brief, needs to be distinct. Often caretakers check to see if the brief or diaper is wet during the night, under low light conditions so they do not wake the user. A distinct color change allows the caretaker to only wake the wearer when a change is needed, not when they are checking. Also, the color should change within minutes of being insulted.
Humidity resistance: Wetness indicators are subjected to all kinds of conditions during manufacturing, storage and transportation, while on the shelf and post purchase. One of the costliest failures of a wetness indicator is the premature indication of wetness. When this happens, it is usually a reaction to humidity in the air, and it can show up as few spots in the indicator or as continuous color change. Either way, when the wetness indicator prematurely indicates, the product is often disposed of unused, creating unnecessary waste and customer dissatisfaction.
Thermal stability: Because very little indicator is used on each brief, the wetness indicator can sit in a heated tank for much longer than a typical nonwoven hot melt. The indicator should be able to remain in the tank for at least a weekend, or two-day period, without impacting its performance or showing signs of charring... Because the wetness indicator may not look different after extended thermal exposure, manufacturers should test it to verify that the exposure to heat did not remove its ability to change color.
Clean machining: As with any nonwoven hot melt, a wetness indicator needs to machine properly to meet line speeds without sputtering or inconsistently depositing hot melt to the product.
Adherence to poly backsheet: Finally, a wetness indicator must effectively stick to the poly backsheet. If it becomes separated from the backsheet, there is a risk that the end user may not be able to see the color change.
Wetness indicators are not only useful features of adult incontinence products and baby diapers, wetness indicators can help differentiate one product from another.

Mack Wei is Nonwovens Sales and Technical Manager, Asia Pacific, at H.B. Fuller. He can be reached at

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