Toilet Paper Softness Testing: Standards, Methods, and Instrumental Evaluation

Toilet paper softness testing quantifies the tactile gentleness and flexibility of bathroom tissue using standardized instruments such as slanted-slot softness testers and handle meters. This technical guide explains the test principle, applicable standards including GB/T 8942, ASTM D2923, TAPPI T498, and ISO 12625-12, as well as specimen preparation, test procedures, and how softness results expressed in millinewtons are applied in quality control and product development.

Technical Overview

Softness is one of the most decisive quality attributes of toilet paper, directly influencing consumer perception, brand preference, and market competitiveness. Because "softness" is fundamentally a tactile sensation, it is generally described as a combination of two components: surface softness, which relates to fiber smoothness and the gentle feel of the sheet surface, and bulk softness, which relates to the flexibility and compressibility of the multi-layer sheet structure.

Since subjective perception cannot be used directly for quality control, instrumental methods have been developed to provide reproducible, quantitative results. In these methods, a conditioned specimen is forced through a narrow slot by a blunt blade or plunger, and the peak resistance force is recorded. The result is expressed in millinewtons (mN), where a lower value indicates a softer sheet. Widely referenced standards include GB/T 8942 (paper softness determination by the slanted-slot method), GB/T 20810 (the Chinese product standard for toilet paper), ASTM D2923 (flexural stiffness of sheet materials by the handle meter method), TAPPI T498 (softness of sanitary tissue), and the ISO 12625 series for tissue paper and tissue products.

Testing Samples

Toilet Paper and Bathroom Tissue

Rolled toilet paper is the primary sample type for softness testing. Specimens are taken from finished rolls after the wound tension has relaxed, typically at least 24 hours after converting. Samples should be free from embossing damage, perforation defects, and moisture exposure.

Facial Tissue and Handkerchief Tissue

Facial tissue products covered by standards such as GB/T 20808 are tested with the same softness methodology. Because these products are often softer and lighter than toilet paper, appropriate slot widths and instrument ranges must be selected to ensure valid measurements.

Paper Towels and Napkins

Kitchen towels, hand towels, and table napkins may also be evaluated for handle and flexibility, although their higher basis weight and wet-strength additives generally result in higher stiffness values compared with toilet tissue.

Specimen Conditioning and Preparation

Prior to testing, samples shall be conditioned in a standard atmosphere of 23 ± 1 °C and 50 ± 2 % relative humidity in accordance with ISO 187. Specimens are cut to the dimensions required by the instrument, commonly approximately 100 mm × 100 mm, taken from multiple positions across the web and from both machine and cross directions. Testers should avoid touching the measurement area, as skin oils and creasing can alter the results.

Testing Items

A comprehensive softness evaluation typically includes the following measurable parameters:

• Softness value (mN): the peak force required to press a specimen into a defined slot, measured with a slanted-slot softness tester.
• Handle or flexural resistance: the combined bending and surface friction response obtained with a handle meter.
• Bending stiffness: determined in accordance with ISO 12625-12 to characterize the rigidity of the tissue structure.
• Surface and total softness indices: derived from advanced tissue softness analyzers that separate surface texture contributions from structural stiffness contributions.
• Supporting properties: grammage (ISO 12625-6), thickness and bulk (ISO 12625-3), and tensile strength (ISO 12625-4), which help interpret softness results in the context of the overall sheet design.

Testing Methods

Slanted-Slot Softness Method (GB/T 8942)

In this method, a rectangular specimen is placed over a narrow slanted slot and a blunt blade descends at constant speed, pressing the sample into the slot until it bottoms out and ruptures the free fold. The maximum force recorded during the stroke is reported as the softness value. The test principle is that a softer, more compliant sheet deforms into the slot with less resistance.

Key elements of the procedure include:

• Selecting the appropriate slot width, commonly 10 mm for toilet paper, based on the expected stiffness range of the product.
• Clamping the specimen flat over the slot without pre-tensioning or wrinkling.
• Running the blade at the specified constant speed and recording the peak force in millinewtons.
• Discarding the first stroke of each specimen if required by the standard and repeating the test on multiple specimens, typically no fewer than ten, in both principal directions.
• Calculating the arithmetic mean and reporting it as the softness result, with a lower mean indicating a softer product.

Handle Meter Method (ASTM D2923 / TAPPI T498)

The handle meter method measures the resistance of a specimen draped over a slot when a blade pushes it into the opening. The measured response combines bending stiffness with surface friction against the slot edges, making it a practical overall "handle" value. Interchangeable slot widths (for example 5 mm, 10 mm, and 20 mm) allow the tester to match the instrument sensitivity to the product type. Results may be reported in millinewtons or grams-force, and this method is widely applied to sanitary tissue, towels, and nonwoven sheet materials.

Bending Stiffness (ISO 12625-12)

For a more fundamental characterization of structural rigidity, bending stiffness is measured on dedicated bending testers in accordance with ISO 12625-12. This parameter isolates the mechanical stiffness of the ply structure from surface effects and is particularly useful in research and development when comparing creping, embossing, or through-air drying (TAD) process changes.

Instrumental Analyzers and Sensory Panels

Modern tissue softness analyzers use a rotating blade sensor that sweeps the specimen surface, capturing vibration and force signals that are mathematically separated into surface softness and stiffness components. These instruments correlate well with human perception and support rapid production monitoring. For final validation, trained sensory panels perform paired comparison or ranking tests under controlled conditions, providing the reference against which instrumental methods are calibrated.

Applications

• Mill quality control: routine softness monitoring during tissue production to verify conformance with internal limits and product standards such as GB/T 20810.
• Product development: comparing fiber furnishes, pulp refining levels, softener chemistry, crepe ratios, embossing patterns, and TAD structures to optimize the softness-to-strength balance.
• Product grading and certification: demonstrating compliance with national or buyer specifications for product registration, labeling, and market access.
• Competitive benchmarking: objective comparison of a product against competitor grades to support positioning and marketing claims.
• Trade acceptance and dispute resolution: independent verification of softness values by accredited third-party laboratories for import, export, and supplier qualification.
• Process troubleshooting: identifying changes in softness that indicate drift in drying, calendering, or reel handling conditions.

FAQ

What unit is used to report toilet paper softness?

Softness is reported in millinewtons (mN). A lower value corresponds to a softer sheet because less force is needed to deform the specimen into the measurement slot.

How does softness differ from bulk?

Bulk describes the thickness per unit basis weight and describes the volume of the sheet, whereas softness describes the tactile response. Bulky sheets are frequently softer, but creping quality, fiber type, and surface treatment also strongly influence the measured softness value.

Which slot width should be used?

The slot width is selected according to the expected stiffness of the product. A 10 mm slot is commonly used for toilet paper and facial tissue; softer or heavier products may require other widths to keep the measured force within the optimal range of the instrument.

How many specimens should be tested?

A minimum of ten valid specimens per sample is generally recommended, tested in both machine and cross directions, with the mean value reported. Increasing the number of specimens improves the statistical reliability of the result.

Does more plies always mean a softer product?

Not necessarily. Additional plies increase cushioning and perceived thickness, but they also increase bending resistance. The final softness depends on the combined effect of ply count, basis weight, creping, embossing, and chemical treatment.

What is the difference between GB/T 8942 and ASTM D2923?

GB/T 8942 uses a slanted-slot tester that measures the peak force to push a folded specimen through a slot, while ASTM D2923 uses a handle meter that measures the combined bending and surface friction response of a specimen over a slot. Both provide force-based softness indicators, but the apparatus geometry differs, so results are not directly interchangeable.

Can softness testing be applied to recycled-fiber toilet paper?

Yes. The test methods are applicable regardless of fiber source. Products made with recycled fiber often require debonding softeners, higher crepe levels, or multi-ply structures to achieve softness values comparable to virgin-fiber grades.