Many manufacturers and suppliers assume that one AS 4586:2013 result can represent their entire product range. It feels logical—if all tiles in a range share the same body, the same glaze, and the same dimensions, shouldn’t they all produce the same slip resistance?

In practice, the answer is almost always no. Slip resistance is highly sensitive to small variations.
Changes in colour pigmentation, glaze thickness, polishing, surface microtexture, coatings, sealers, anti-slip additives, and even differences between production runs can produce different results during wet pendulum and dry friction testing.

A white matt tile may test at P4, while its charcoal polished counterpart tests at P2. A textured tile may meet D1, while its smoother sibling falls below threshold. These differences can easily lead to non-compliance in real-world installations.

Understanding why results vary—and why comprehensive testing matters—is essential for manufacturers, wholesalers, builders, architects, and certifiers who rely on accurate slip classifications for compliance, safety, and risk management.

How Slip Resistance Varies Between “Identical” Products

Slip ratings are influenced by microscopic differences in surface structure. Even when products appear identical to the naked eye, their underlying microtexture may differ enough to meaningfully alter friction performance.

Key factors that change slip ratings across a product line include:

1. Surface Microtexture

Slip resistance relies heavily on microtexture—tiny peaks and troughs in the surface that interact with the pendulum slider. Small changes in:

• polishing processes
• glaze application
• surface finishing
• curing
• mechanical brushing
• embossing patterns

…all affect traction.

Two tiles that look identical may have microtexture differences that dramatically alter BPN values.

2. Colour and Pigmentation

Pigment concentration affects heat absorption during firing. Darker glazes may cure smoother or harder, reducing microtexture.

Example:

• Light grey matt tile: P4
• Same tile in black gloss: P2

Same body. Same manufacturer. Different rating.

3. Glaze and Surface Coating Thickness

Variations in glaze thickness—even slight ones—change friction. Thicker glazes often smooth out the underlying microtexture, while thin glazes can produce more pronounced grip.

Additionally, matte glazes typically produce higher friction than polished glazes, even when applied to the same tile body.

4. Polishing and Buffing Processes

Polished tiles are especially prone to slip rating variation. Polishing removes part of the upper glaze or coating layer, smoothing peaks and filling troughs. Because polishing is mechanical, outcomes vary by:

• pressure
• duration
• machine grit
• pad composition
• tile hardness

This contributes to unpredictable slip performance or increased risk.

5. Anti-Slip Additives and Granules

Some manufacturers incorporate grip additives or micro-granules into glazes. These disperse inconsistently unless the process is tightly controlled. Variability in granule size and distribution leads to classification differences across the same range.

6. Batch Differences (Kiln, Firing, Heat, Humidity)

Manufacturers regularly experience batch-level variation. Factors include:

• kiln temperature
• humidity
• clay moisture
• glaze consistency
• firing duration

Batch-to-batch slip resistance differences are measurable and routine.

7. Surface Sealers and Post-Production Treatments

Many product lines are sealed or coated after firing. These treatments influence friction, and small inconsistencies can create substantial variation across tiles from the same SKU. Most sealers lower slip resistance—especially solvent-based products.

8. Cleanability and Surface Porosity

Some finishes retain more cleaning residue or microfilm than others, affecting slip readings post-installation. Polished or dark glazes often hold residues more visibly.

Why One Test Cannot Represent All Variants

Testing a single tile from a product line provides information only about that specific sample at that time. It does not:

• speak for all colours
• speak for all finishes
• capture batch variability
• reflect the effect of polishing
• capture sealing or post-treatment changes
• show how coatings interact with texture

Certifiers and purchasers assume that a test report applies to a specific tile type—not the entire range. Misrepresenting results risks audit failure, lost contracts, and costly replacements.

The Consequences of Insufficient Testing

Inadequate testing exposes suppliers and clients to significant risk:

1. Compliance Failures

A tile specified for a wet environment must meet the NCC-referenced slip classification. If a variant within the range performs lower than expected, the project may fail certification.

2. Post-Installation Disputes

A common dispute scenario:

• • The tested sample was P4
  • The installed colour variant is actually P2
  • The builder blames the supplier
  • The supplier blames testing
  • The certifier refuses sign-off

This leads to expensive rectification and reputational damage.

3. Rework and Replacement Costs

Replacing tiles in a finished project often involves demolition, re-tiling, waterproofing, re-grouting, and delayed handover.

4. Financial Liability

If a slip accident occurs, audit evidence will be inspected. If a tile was installed based on a test result from a different variant, legal exposure increases.

5. Certification Rejection

Certifiers frequently reject test reports that only represent a single variant when multiple finishes have been supplied.

AS 4586:2013 – How Testing Is Conducted Across Product Lines

Slip testing of new products is conducted in a laboratory environment under AS 4586 using the wet pendulum method (Appendix A) or the dry floor friction test (Appendix D). Each finish or colour should be tested independently.

For a typical product line, testing should include:

• one sample per colour
• one sample per finish
• one sample per production variant
• any tile that has been polished
• any tile treated with sealer or coating
• textured vs matt vs gloss finishes
• variants intended for internal vs external use

For most manufacturers, this means 3–12 samples per product line.

Why Bulk Testing Is the Most Efficient Approach

Testing variants individually one-by-one can be inefficient. A better model for suppliers is bulk testing, where the entire range is submitted together.

Benefits of bulk testing include:

• streamlined reporting
• consolidated classification documentation
• predictable certification timelines
• consistent equipment and technician conditions
• reduced costs per sample
• easier presentation to certifiers
• clear mapping of the entire product line
• freight savings
• logistics

Bulk testing prevents missing data and provides a complete, defensible record.

When to Retest After Manufacturing Changes

Manufacturers should retest when:

• glaze formulation changes
• polishing process changes
• production shifts to another kiln or facility
• firing schedule or temperature changes
• post-production coatings are updated
• new colours are added
• the tile body composition changes
• the grit used in the surface finish is altered

Retesting ensures continuity of classification.

When Product Lines Require Field Testing (AS 4663:2013)

If tiles have been installed and then sealed, polished, damaged, or contaminated, onsite testing under AS 4663:2013 may be required.

AS 4663:2013 is needed when:

• installation conditions differ from lab conditions
• a variant appears smoother or more polished than expected
• there is visible wear
• sealing or re-sealing has occurred
• clients request proof of performance in situ

Combining AS 4586:2013 (lab) with AS 4663:2013 (field) provides a complete picture.

Choosing the Right Slip Testing Strategy for Product Lines

Manufacturers and importers should:

• test every finish and colour
• retest after process changes
• test samples from each production run for high-risk tiles
• use bulk testing where possible
• document results clearly for certifiers
• confirm NCC requirements before marketing a classification

Architects and builders benefit when suppliers can provide clear, variant-specific AS 4586:2013 certification.