AATCC TM22 vs ISO 4920: What Is the Difference in Fabric Spray Testing?

AATCC TM22 and ISO 4920 are widely used to evaluate the surface water repellency of textile fabrics. Both expose a taut fabric specimen to a controlled water spray and assess the resulting wetting pattern.

Because their purposes and basic principles are closely related, buyers may receive apparently similar reports with different grading systems. One laboratory may report an AATCC spray rating such as 90, while another reports an ISO spray rating such as Grade 4.

These results may represent comparable visual wetting levels, but buyers should not remove the original standard reference or treat a converted rating as though the fabric had been tested under both methods.

What Does AATCC TM22 Measure?

AATCC TM22-2024 is titled Test Method for Water Repellency: Spray Test. It applies to textile fabrics that may or may not have received a water-repellent finish.

Under controlled conditions, water is sprayed against the taut face of a specimen. The resulting wetting pattern is visually compared with the applicable AATCC photographic evaluation scale.

The test is particularly useful for evaluating the effectiveness of durable water-repellent finishes, commonly known as DWR finishes. It may be used on woven, knitted and other textile constructions, although fabric texture can affect visual assessment.

What Does ISO 4920 Measure?

ISO 4920:2012 is titled Textile fabrics—Determination of resistance to surface wetting (spray test). It also applies to fabrics with or without a water-resistant or water-repellent treatment.

Like AATCC TM22, ISO 4920 evaluates the pattern of surface wetting created when water is sprayed onto a mounted textile specimen under controlled conditions.

ISO 4920:2012 was reviewed and confirmed by ISO in 2023, so the 2012 edition remains current at the time of writing.

AATCC TM22 vs ISO 4920: Main Differences

Accuracy note: This comparison summarizes the standards for purchasing decisions. Laboratories must follow the complete official edition requested by the buyer. The official standards—not a general comparison table—control specimen preparation, apparatus, evaluation and reporting.

How Do the Two Rating Scales Compare?

The rating systems use different numbers to describe similar degrees of visible surface wetting. AATCC reports commonly use values from 100 at the highest end to 0 at the lowest end. ISO reports commonly use Grade 5 at the highest end and Grade 0 at the lowest end.

Accuracy note: This table is a practical guide to commonly aligned reporting levels. It does not replace either organization’s official photographic scale or authorize a laboratory to report a result under a method it did not perform.

Can AATCC TM22 and ISO 4920 Results Be Converted?

A buyer may use the corresponding rating levels as a convenient way to understand reports from different markets. However, three rules should be followed.

Keep the Original Test Method

If a laboratory tested according to AATCC TM22, the final report should continue to identify AATCC TM22 and its original result. The result should not be relabeled as ISO 4920 unless the laboratory actually performed and reported the ISO method.

Do Not Treat Conversion as Retesting

Changing “AATCC 90” to “ISO Grade 4” in a spreadsheet does not create an ISO 4920 test result. It is only a comparison for communication purposes.

Check the Buyer’s Contractual Requirement

If a specification names ISO 4920, a report issued only to AATCC TM22 may require buyer approval before it can be accepted. The reverse is also true. Similarity between the methods does not automatically override a purchase specification, customer manual or regulatory document.

Do the Tests Prove a Fabric Is Waterproof?

No. Both methods assess resistance to surface wetting. They do not determine how much water pressure is required to penetrate the fabric.

A fabric can show excellent water beading during a spray test but still leak under hydrostatic pressure. This may occur with lightweight woven fabrics, breathable constructions or materials without a continuous coating or membrane.

A coated or laminated fabric can also resist water penetration while its outer face begins to wet. Surface repellency and water-penetration resistance are related purchasing considerations, but they are not the same property.

Accuracy note: Test selection depends on the applicable product specification and intended exposure. Results obtained from different properties or test methods should not be treated as interchangeable.

Which Standard Should a Buyer Choose?

Choose the Standard Named by the Customer

If the brand manual, purchase order or finished-product standard specifies AATCC TM22 or ISO 4920, use that exact method and edition. This prevents disagreements during laboratory approval and final inspection.

Consider the Target Market

AATCC TM22 is widely recognized in U.S.-oriented textile supply chains. ISO 4920 is commonly used for international sourcing and in specifications built around ISO or EN methods. Market usage is a practical consideration, not a technical claim that one method is universally superior.

Use One Reporting System Consistently

When comparing several suppliers, request the same method, edition, conditioning procedure and acceptance level from each supplier. Comparing one supplier’s AATCC result with another supplier’s ISO result can introduce unnecessary uncertainty, even when the general wetting levels appear similar.

Request Both Only When Necessary

Testing to both methods may be justified when the same fabric will be supplied to customers using different specifications. For most projects, one clearly selected method is more efficient than automatically requesting two similar spray tests.

Why Initial and Post-Laundering Results Matter

A new DWR-treated fabric can show strong initial water beading, but outdoor apparel and washable products also require performance after care and use.

Detergent residue, abrasion, contamination, repeated flexing and drying conditions can affect the surface treatment. The number of laundering cycles and the care procedure must therefore be agreed before testing.

A useful sourcing specification should state:

• The required initial spray rating.
• The applicable test method and edition.
• The laundering or cleaning method.
• The required number of care cycles.
• The drying procedure.
• Whether heat reactivation is permitted before evaluation.
• The required rating after care.

What About PFC-Free DWR Fabric?

Fluorine-free or PFC-free DWR systems can provide useful resistance to surface wetting, but the chemistry name does not guarantee a particular AATCC TM22 or ISO 4920 result.

Finished performance can be influenced by:

• Fiber composition and yarn structure.
• Fabric density, weight and surface texture.
• Dyeing, printing and washing processes.
• DWR application level and distribution.
• Drying and curing conditions.
• Softeners, wicking agents and other chemical finishes.
• Laundering, abrasion and contamination during use.

Buyers should evaluate the actual production-representative fabric rather than relying only on a chemical supplier’s general data or a result obtained from a different construction.

How to Compare Two Laboratory Reports

Before deciding that two spray-test results are equivalent, check the following information:

Recommended Fabric Inquiry Format

Instead of requesting only “waterproof fabric” or “spray test passed,” provide a complete brief:

• End use: jacket, pants, backpack, tent, awning, umbrella or equipment cover.
• Target market: country, customer and relevant product specification.
• Fabric specification: fiber, yarn, construction, weight and width.
• Color and finishing: final colorway, print, coating, lamination and DWR route.
• Spray-test method: AATCC TM22-2024 or ISO 4920:2012.
• Initial requirement: required original spray rating.
• Durability requirement: care procedure, cycle count and post-care rating.
• Additional performance: hydrostatic pressure, breathability, seam leakage, abrasion, colorfastness or weathering as needed.

Common Buyer Mistakes

• Assuming AATCC TM22 and ISO 4920 measure waterproofness.
• Removing the original test method when converting a rating for comparison.
• Requesting “pass” without defining a minimum acceptable grade.
• Comparing initial data from one supplier with washed data from another.
• Using a test result from one color or construction to approve every fabric variation.
• Ignoring the standard edition on a laboratory report.
• Assuming a PFC-free finish automatically provides durable spray-test performance.
• Evaluating the fabric but ignoring seams, zippers and finished-product construction.

Frequently Asked Questions

Are AATCC TM22 and ISO 4920 the same test?

They evaluate the same general property using closely related spray-test principles, but they are separately published standards with different references and rating formats. Buyers should request and report the exact method named in the specification.

Is AATCC 90 equal to ISO Grade 4?

These ratings are commonly treated as corresponding visual levels. However, the original test method must remain on the report, and a comparison does not mean that the specimen was formally tested under both standards.

Which method is more difficult to pass?

Neither method has one universal pass/fail requirement. The buyer or applicable product specification defines the required result. Because the methods are closely related, report conditions and acceptance criteria are often more important than asking which standard is generally “harder.”

Can a fabric pass the spray test and still leak?

Yes. The spray test assesses surface wetting, not resistance to water penetration under pressure. Hydrostatic-pressure or product-level rain testing may also be required.

Should the test be performed after washing?

Yes, when the product is expected to maintain water repellency after care. The wash method, cycle count, drying process and any permitted reactivation treatment must be defined.

Can one report cover all colors?

Not automatically. Dyeing, printing and finishing variations can affect surface repellency. Buyers should establish a representative or risk-based color-testing plan.

Final Recommendation

AATCC TM22 and ISO 4920 are closely related tools for evaluating resistance to surface wetting. Their main practical differences concern the issuing organization, standard reference, market preference and rating format—not a fundamentally different water-repellency property.

For reliable supplier comparison, select one required method and edition, define the minimum initial and post-care results, and test the final production-representative construction. Add hydrostatic-pressure, rain, impact-penetration or finished-product testing when the application requires protection from water passing through the material.

Technical references: AATCC TM22-2024, Test Method for Water Repellency: Spray Test; ISO 4920:2012, Textile fabrics—Determination of resistance to surface wetting (spray test). This guide does not reproduce or replace either official standard.