How Towels Are Tested: Absorbency, Strength, Shrinkage and Colorfastness

A towel may feel soft in a showroom and still perform poorly after ten washes.

It may absorb water beautifully but lose color. It may look dense and luxurious but shrink substantially. It may survive laundering yet have a weak ground structure that fails under repeated pulling.

That is why professional towel evaluation does not rely on touch, appearance or a single specification such as GSM.

There Is No Single “Towel Quality Test”

ASTM D5433 is particularly useful because it treats household and institutional towel performance as a collection of independent characteristics rather than one overall score.

The current ASTM D5433-24 specification covers woven and knitted kitchen towels, dishcloths, crash towels, huck towels, washcloths, hand towels, bath towels and bath sheets. It addresses properties including strength, dimensional change, skew, colorfastness, absorbency and laundered appearance.

Importantly, ASTM also notes that purchaser and supplier may agree on different performance requirements depending on the intended product. A lightweight travel towel and a dense hotel bath towel do not necessarily need identical targets.

Before Testing: Samples Have to Be Conditioned

Textile properties respond to moisture and temperature.

Cotton in particular is hygroscopic, meaning its equilibrium moisture content changes with ambient humidity. That can affect mass and mechanical behavior.

Professional textile testing therefore uses controlled atmospheric conditioning so that one laboratory does not test a very dry specimen while another tests the same textile after it has absorbed much more atmospheric moisture.

Standardization is one of the less visible but most important parts of textile testing: a measurement only becomes useful when the test conditions are reproducible.

Absorbency Is Not One Property

When a consumer says a towel is absorbent, several different things may be happening:

• Water wets the surface quickly
• The towel removes liquid efficiently from skin
• Water moves away from the contact point through capillary channels
• The fabric retains a large total volume of water

These behaviors are related, but they are not interchangeable.

AATCC TM79 is a general absorbency method applicable to textiles of varied fiber content and construction. AATCC also maintains separate methods for liquid moisture management and wicking, reinforcing the fact that moisture performance has multiple dimensions.

How Terry Towels Are Tested for Surface Water Absorption

ASTM D4772-26 is specifically designed to evaluate the ability of a terry fabric to rapidly absorb and retain liquid water from surfaces such as human skin, dishes and furniture.

That sounds straightforward, but one of the most technically important details is what the standard does not cover.

ASTM states that D4772 is not applicable to non-terry structures such as:

• Huck towels
• Waffle-weave towels
• Crash towels
• Flour-sack towels
• Nonwoven wipes

The reason is structural. The angled test arrangement may allow water to run off or pass through lightweight, open, non-pile fabrics in a way that does not fairly represent their actual ability to dry a surface.

Why a “Drop Test” Is Not the Whole Story

Informal demonstrations often place a water droplet on a towel and time how quickly it disappears.

That can reveal surface wetting, but it does not by itself tell you:

• How much total water the towel can hold
• How effectively it removes water from skin
• How far the water spreads through the textile
• How quickly the towel dries afterward

Finishes can also change initial wetting dramatically. A towel may appear slow in a drop test because of a temporary surface treatment while still having substantial ultimate water capacity.

Strength Testing: Can the Towel Survive Mechanical Stress?

A towel experiences substantial mechanical stress during its life.

It is pulled from rails, twisted, washed, spun at high speed, tumble dried and repeatedly stretched while wet.

Strength testing asks whether the underlying textile structure can tolerate those stresses.

ASTM D5433 specifies breaking-strength requirements for woven terry and non-terry towels. For bath towels, hand towels, washcloths and bath sheets, the older published table reproduced by ASTM lists minimum breaking strengths in both the length and width directions, demonstrating another important point: fabric direction matters.

Warp and Weft Strength Can Be Different

Woven towels contain different yarn systems running in different directions.

Yarn count, yarn type, density and interlacing can differ between length and width, so a fabric may resist force differently depending on the direction of pull.

Professional specifications therefore commonly require testing in both principal fabric directions.

Breaking Strength Is Not the Same as Tear Strength

A towel can perform well in one mechanical test and less well in another.

Deep loop terry, for example, introduces snagging considerations that are not captured by a basic breaking-strength result.

How Breaking Strength Is Measured

In a tensile test, a standardized fabric specimen is gripped between clamps and pulled under controlled conditions until the material breaks.

The machine records the maximum force sustained.

Textile laboratories use several standardized approaches depending on the product and specification, including grab and strip methods.

The important point is reproducibility: specimen width, clamp arrangement, extension rate and gauge length must be controlled so results from different samples can be meaningfully compared.

What About Knitted Towels?

Some towel products are knitted rather than woven.

ASTM D5433 recognizes this difference and includes bursting strength for knitted constructions. Bursting tests apply pressure across an area rather than pulling only along one linear direction, making them useful for structures whose deformation is more multidirectional.

Shrinkage Testing Is Really Dimensional-Stability Testing

Consumers call it shrinkage. Textile laboratories usually speak more broadly about dimensional change.

That is because a fabric can shrink, grow or distort.

AATCC TM135-2025 determines length and width changes in fabrics subjected to standardized home laundering. The method provides multiple washing temperatures, agitation cycles and drying procedures to represent common care conditions.

Standard laundering procedures are intentionally fixed so different textiles can be compared consistently—even though real household machines and habits vary.

How Shrinkage Is Calculated

The laboratory marks or measures known distances on a conditioned specimen before laundering.

After the specified wash and drying cycles, those distances are measured again.

Dimensional change is reported as a percentage relative to the original dimension.

If a marked length becomes shorter, the fabric has shrunk in that direction. If it becomes longer, the fabric has grown.

Why Towels Shrink

Several mechanisms can contribute:

• Relaxation of tensions introduced during weaving and finishing
• Fiber swelling during wetting
• Yarn rearrangement
• Compaction during washing and tumble drying
• Differences between pile and ground structures

Cotton towels can be particularly responsive because cellulose fibers swell in water and because woven structures may relax after the tensions of manufacturing are removed.

Why Length and Width Shrinkage Are Tested Separately

Warp and weft yarn systems are not necessarily identical.

A towel might therefore contract more in one direction than the other.

ASTM towel specifications recognize separate dimensional-change requirements for length and width. This is important because uneven change can alter proportions, distort borders or make a towel look visibly misshapen even when total area loss is modest.

Skew Is Different From Shrinkage

A fabric can retain roughly similar dimensions while its yarn system moves out of square.

That distortion is called skew or skewness.

AATCC TM179 is specifically dedicated to skew change in fabrics after home laundering. ASTM D5433 also includes skew among the performance characteristics relevant to towel products.

For towels with borders, stripes or geometric patterns, skew can be visually obvious even when the fabric remains fully functional.

Appearance After Laundering Is Also a Performance Test

Laboratory performance is not limited to numbers from machines.

Repeated washing can alter:

• Pile loft
• Surface smoothness
• Border appearance
• Wrinkling
• Puckering
• Overall visual quality

ASTM D5433 therefore includes laundered appearance as a performance characteristic rather than assuming a towel is acceptable merely because it did not break or shrink excessively.

Colorfastness: Will the Color Stay Where It Belongs?

“Colorfast” does not mean one thing.

A dye can resist laundering but transfer when rubbed wet. Another can resist rubbing but fade badly under light.

AATCC therefore maintains different methods for different exposures.

Colorfastness to Laundering

AATCC TM61 is an accelerated laundering test.

Instead of waiting through months of household washing, a laboratory exposes the specimen to controlled washing conditions designed to evaluate color change and staining more efficiently.

Two different outcomes matter:

• Shade change: did the towel itself become lighter, darker or otherwise change color?
• Staining: did dye transfer from the towel onto adjacent test fabrics?

ASTM D5433 includes requirements for both shade change and staining after laundering.

What Is Crocking?

Crocking means transfer of color from one textile surface to another through rubbing.

In AATCC TM8, a standardized white test cloth is rubbed against the dyed specimen using a crockmeter.

Testing is commonly performed in both dry and wet conditions because wet rubbing can mobilize dyes differently from dry rubbing.

ASTM's towel performance specification historically sets a stricter minimum for dry crocking than wet crocking—reflecting the reality that wet color transfer is often more challenging.

Why Wet Crocking Matters for Towels

Towels are unusual among home textiles because they routinely contact wet skin.

A deep-colored towel that looks perfectly stable while dry may still transfer color when damp and rubbed against:

• Skin
• White robes
• Light-colored laundry
• Bathroom surfaces

That makes wet crocking especially relevant to towel quality.

Colorfastness to Light

Light can break down dye molecules over time.

AATCC TM16.3 uses xenon-arc exposure to evaluate lightfastness under controlled conditions intended to simulate important portions of sunlight exposure.

This is particularly relevant to:

• Towels stored beside bright windows
• Beach towels
• Pool towels
• Deep or highly saturated shades

ASTM D5433 includes lightfastness among the color-performance requirements for towel products.

How Color Change Is Graded

Colorfastness often uses standardized visual scales rather than simply “pass” or “fail.”

AATCC Evaluation Procedure 1 covers the Gray Scale for Color Change, while Evaluation Procedure 2 covers the Gray Scale for Staining. Instrumental procedures can also quantify color differences and staining.

This allows laboratories and suppliers to communicate performance with a common rating system rather than subjective descriptions such as “hardly faded.”

Why One Wash Is Not Enough

Many defects develop cumulatively.

Repeated laundering can expose:

• Progressive shrinkage
• Color loss
• Pile flattening
• Seam weakness
• Border distortion
• Surface fuzzing

A sample that looks excellent after one wash may behave differently after five, ten or twenty cycles.

Buyers therefore often create internal protocols that go beyond the minimum standard and evaluate appearance or dimensions after multiple laundering cycles.

Why Laboratory Results Need Tolerances

Textiles contain natural and manufacturing variability.

Even specimens cut from the same towel may not produce perfectly identical numerical results.

Professional testing therefore relies on:

• Defined specimen sizes
• Replicate tests
• Controlled conditioning
• Specified test speeds and loads
• Statistical interpretation

ASTM D4772 explicitly discusses laboratory bias and statistical comparison when results from different laboratories disagree.

This is another important difference between laboratory testing and a social-media product demonstration.

What a Serious Towel QC Program Might Test

Product-specific programs may go further by testing drying time, linting, snagging, abrasion, chlorine resistance, chemical residues or other properties relevant to the intended customer.

Why Hotel Towels and Household Towels May Need Different Targets

Test methods can be standardized while performance specifications remain product-specific.

A hotel towel may be subjected to:

• Far more wash cycles
• Commercial tumble drying
• Stronger bleaching systems
• Higher mechanical processing

A decorative household towel may prioritize color and softness differently.

ASTM D5433 explicitly recognizes that performance requirements can be modified by agreement between purchaser and supplier.

Standards provide a common technical language. They do not eliminate the need to define what “acceptable” means for a particular product.

How to Read a Towel Test Report

A meaningful test report should identify at least:

• The test method and version
• The specimen tested
• The conditioning or laundering procedure where relevant
• The units of measurement
• The required limit or internal target
• The measured result
• Whether the sample passed

A statement such as “tested for absorbency” is much less informative than: which method, under what conditions, and against what requirement?

Common Testing Mistakes

Frequently Asked Questions

How is towel absorbency tested?

It depends on the towel structure and the property being measured. ASTM D4772 evaluates rapid surface-water absorption of terry fabrics, while AATCC TM79 provides a broader textile absorbency method.

Can the same absorbency test be used for terry and waffle towels?

Not always. ASTM D4772 specifically excludes waffle, huck and other non-terry fabrics because the apparatus can produce misleading runoff or pass-through results for those structures.

How do laboratories test towel shrinkage?

Reference dimensions are measured before standardized laundering and measured again afterward. AATCC TM135 provides controlled washing and drying procedures for determining fabric dimensional change.

What is towel crocking?

Crocking is transfer of color from the towel to another surface through rubbing. It can be tested under both dry and wet conditions.

What is the difference between colorfastness and fading?

Fading is one type of color change. Colorfastness is broader and describes resistance to specific exposures such as laundering, rubbing, light, water or perspiration.

Does higher GSM mean a towel will pass strength tests?

No. GSM measures fabric mass per unit area. Strength depends on yarn, ground structure, density and construction, so it must be tested directly.

Why are towels tested in length and width directions?

Warp and weft systems can have different yarns, densities and mechanical properties, so breaking strength and dimensional change may differ by direction.

What does a towel need to pass ASTM D5433?

ASTM D5433 provides performance requirements covering multiple properties for defined towel categories. Specific purchasing requirements can also be modified by agreement between buyer and supplier.

Final Takeaway

Good towel testing separates properties that consumers often collapse into one vague idea of “quality.”

Absorbency asks how water interacts with the textile. Strength asks whether the structure can tolerate force. Dimensional testing asks whether the towel remains stable after laundering. Colorfastness asks whether the dye remains both visually stable and where it belongs.

None of those results can be replaced by GSM, softness or appearance.

The most credible towel evaluation therefore uses the right standardized method for the right construction, tests the textile under controlled conditions and looks at several performance categories together.

That is how a towel moves from “feels good in the hand” to a product whose performance can actually be specified, measured and compared.

References

1. ASTM International. ASTM D5433-24, Standard Performance Specification for Towel Products for Institutional and Household Use. Source
2. ASTM International. ASTM D4772-26, Standard Test Method for Surface Water Absorption of Terry Fabrics (Water Flow). Source
3. AATCC. TM79, Absorbency of Textiles. Source
4. AATCC. TM195, Liquid Moisture Management Properties of Textile Fabrics. Source
5. AATCC. TM197, Vertical Wicking Rate of Textiles. Source
6. AATCC. TM198, Horizontal Wicking of Textiles. Source
7. AATCC. TM135-2025, Dimensional Changes of Fabrics after Home Laundering. Source
8. AATCC. TM179, Skew Change in Fabrics After Home Laundering. Source
9. AATCC. TM61, Colorfastness to Laundering: Accelerated. Source
10. AATCC. TM8, Colorfastness to Crocking: Crockmeter. Source
11. AATCC. TM116, Colorfastness to Crocking: Rotary Vertical Crockmeter. Source
12. AATCC. TM16.3, Colorfastness to Light: Xenon-Arc. Source
13. AATCC. TM15, Colorfastness to Perspiration. Source
14. AATCC. TM107, Colorfastness to Water. Source
15. AATCC. TM162, Colorfastness to Water: Chlorinated Pool. Source
16. AATCC. EP1, Gray Scale for Color Change. Source
17. AATCC. EP2, Gray Scale for Staining. Source
18. AATCC. EP7, Instrumental Assessment of Change in Color of a Test Specimen. Source
19. AATCC. EP12, Instrumental Assessment of Degree of Staining. Source
20. ASTM International. ASTM D5034, Standard Test Method for Breaking Strength and Elongation of Textile Fabrics (Grab Test). Source
21. ASTM International. ASTM D5035, Standard Test Method for Breaking Force and Elongation of Textile Fabrics (Strip Method). Source
22. ASTM International. ASTM D3786/D3786M, Standard Test Method for Bursting Strength of Textile Fabrics—Diaphragm Bursting Strength Tester Method. Source
23. ASTM International. ASTM D2261, Standard Test Method for Tearing Strength of Fabrics by the Tongue Procedure. Source
24. AATCC. TM93, Abrasion Resistance of Fabrics: Accelerotor. Source
25. AATCC. Laundering Module: Dimensional Stability, Skew, Seam Performance and Appearance after Home Laundering. Source
26. AATCC. Colorfastness Module. Source