Why Pigment Digital Prints Have Poor Wet Rubbing Fastness: Binder, Pretreatment and Curing Causes

Poor wet rubbing fastness in pigment digital printing can result from exposed surface pigment, weak binder adhesion, unsuitable pretreatment deposition or incomplete curing. This guide explains how to isolate the cause and improve durability without sacrificing color yield, fabric hand or production efficiency.

A pigment digital print can look sharp, feel dry and pass a dry rubbing check, yet transfer substantial color to a wet test cloth. Increasing binder or raising the dryer temperature may help one sample and make the next sample stiffer, darker or less consistent. The reason is simple: similar wet rubbing failures can originate in different parts of the printing system.

Poor wet rubbing fastness means the printed surface cannot adequately resist color transfer under the specified combination of water and rubbing. It does not, by itself, identify insufficient binder, excessive pretreatment or inadequate curing. The first useful question is where the transferred color comes from and which controlled change reduces that transfer.

This guide provides a diagnostic sequence for textile printers, finishing teams, quality managers and chemical buyers. Start by aligning the test, distinguish print failure from substrate failure, verify the thermal process, and then investigate binder performance and pretreatment deposition. Judge every improvement against the complete finished-fabric specification.

What Wet Rubbing Failure Actually Tells You

Pigments are insoluble colorants held on the textile through a binder-containing system. Unlike a dye process designed to build affinity or chemical bonding between a dissolved dye and a fiber, pigment printing depends heavily on the integrity of the deposited layer and its attachment to the textile. A colored wet crock cloth does not mean that the pigment simply dissolved in water.

Water can change how the printed assembly responds to friction. Depending on the materials, it may affect the polymer layer, residual water-sensitive components, the interface with the fiber or the fiber itself. Rubbing then removes accessible color-bearing material. Identifying the vulnerable part of this assembly is more useful than treating the grade as a direct measurement of binder quantity.

Separate the possible failure mechanisms

• Accessible surface pigment: colorant remains insufficiently protected at the surface.
• Weak cohesion: the deposited layer breaks within itself during rubbing.
• Weak adhesion: the layer detaches from the substrate or another printed layer.
• Water-sensitive behavior: wetting weakens some part of the deposited assembly.
• Substrate transfer: colored fibers, loose lint or background dye contribute to the stain.

These are diagnostic hypotheses, not conclusions that can be read directly from a staining grade. Examine the rubbed fabric and crock cloth together, preferably with suitable magnification. Loose colored fibers suggest a different investigation from a smooth color smear or visible film fragments, but appearance alone cannot conclusively identify the transferred material.

Wet rubbing, dry rubbing and washing answer different questions

Dry rubbing, wet rubbing and laundering evaluate different exposures. Agree the required tests separately. AATCC TM8 also notes that subsequent treatments can change color transfer, so state whether the required rubbing result is measured before laundering, after the specified laundering, or at both stages. Passing washing does not establish a passing wet rubbing grade. AATCC TM8 purpose and scope

For dark fabrics, include an unprinted control from the same lot. If the background itself transfers color, changing the pigment pretreatment may never fully resolve the measured failure. A pretreated but unprinted control can further show whether pretreatment or heating changes the behavior of the base fabric.

Confirm the Test Before Changing Binder, Pretreatment or Curing

First confirm that the reported failure is reproducible under the buyer’s agreed method. AATCC TM8 evaluates color transfer by rubbing a textile with a white cloth under controlled conditions, with dry and wet procedures. ISO 105-X12 also addresses rubbing fastness. Use the specified method and edition; do not assume that results obtained under different procedures are interchangeable. [1] [2]

Keep retained cuttings and labeled test cloths from both passing and failing production. Record individual results and their locations rather than reporting only a convenient average. If one edge repeatedly fails while the center passes, that spatial pattern is valuable process evidence.

Small motifs require particular care. A rubbing path that crosses several colors or unprinted fabric may not represent the intended area. AATCC identifies limitations for small printed areas in TM8 and provides a rotary vertical crockmeter method, TM116, for a different test configuration. Any alternative must be agreed with the buyer; it should not be selected simply because it produces a better grade. [1] [7]

Set the acceptance criteria before trialing a correction. Include wet and dry rubbing, shade tolerance, required laundering performance and an approved hand reference. Otherwise, a technically improved rubbing result may become an unacceptable finished product.

Build a Registered Transfer-Evidence Record

Keep the test cloth and the rubbed textile linked to the same specimen and track. A staining grade records the agreed test outcome; a photograph or fiber observation supports diagnosis but does not replace that grade. Use the complete buyer-specified method, with its required conditioning, cloth preparation and assessment procedure.

Photograph the cloth and textile before and after testing under consistent lighting and scale. Suitable magnification may reveal colored fibers, loose particles or film fragments. Such observations narrow the investigation but cannot prove chemical identity, binder deficiency or inadequate cure. If identifying the transferred material changes the remedy, use an appropriate analytical method rather than naming it from appearance alone.

Record individual dry and wet grades by specimen, width position, print coverage and tested direction, including the weakest relevant result. Do not convert a half-grade change into a percentage improvement or conceal a failed position in an average. Retest using independent specimens when a borderline result or production variation affects the release decision.

Choose the next bounded comparison from that paired evidence: substrate preparation if the blank transfers, treatment/thermal compatibility if the treated-only control changes, or print-layer protection and exposure if failure is specific to the printed assembly. More than one cause may remain. Reproduce a correction at the required shade, hand and production loading before release.

Binder-Related Causes: Quantity Is Only Part of the Problem

Identify where the binder actually comes from

In pigment inkjet systems, binder functionality may be supplied through the ink, pretreatment, a separately applied layer or a combination of these. Commercial suppliers offer distinct ink-binder and pretreatment technologies, illustrating why these roles should not be treated as interchangeable. [4] Ask for the approved system architecture before deciding which component to increase.

A pretreatment that improves pigment immobilization is not automatically the principal binder. Similarly, a high-solids product is not necessarily rich in the polymer responsible for final rubbing resistance. Its solids may include other functional components. For a fuller explanation of these roles, see pigment digital printing pretreatment versus binder.

Too little effective film protection

An insufficiently protective layer can leave pigment accessible to friction. However, “insufficient” refers to effective protection at the relevant location, not just the amount of binder charged into a vessel. Uneven application, penetration away from the surface, poor film development or an unsuitable combination of layers can make a nominally adequate addition perform poorly.

Investigate deposit uniformity and the approved ink–pretreatment relationship before increasing concentration. A correction that improves only heavily treated areas while leaving other areas weak may be masking application variation. More chemistry across the entire width can add stiffness and cost without eliminating the underlying distribution problem.

Unsuitable adhesion, flexibility or wet resistance

A binder must function on the actual fabric and with the other materials present. Fiber composition, surface finish, prior processing and print coverage can change the demands placed on the deposited layer. A material that performs well on one cotton construction should not automatically be approved for a polyester-rich blend or a different finishing route.

Do not rank binders by hardness alone. A harder layer may resist one form of abrasion but compromise flexibility; a softer layer may provide good durability when properly designed and applied. Evaluate wet rubbing together with flexing, hand and laundering requirements. The practical objective is a durable, compatible layer at an acceptable deposit level.

Adding binder to the ink is not a routine production adjustment

Inkjet inks must meet requirements for jetting, stability and printhead compatibility. An unapproved binder addition can alter these properties even if a hand-coated laboratory sample appears stronger. Corrective work should use supplier-approved ink, pretreatment or finishing options at their intended application stage. Do not use a successful crocking result to justify modifying ink outside the printer and ink supplier’s requirements.

For proprietary materials, request the operational information needed to evaluate the system: compatible substrates, application limits, drying and curing requirements, and recommended tests. Do not estimate undisclosed binder content from product viscosity or total solids.

Pretreatment-Related Causes: Strong Color Can Hide a Weak Surface

Pretreatment controls how ink interacts with the textile. Better surface retention can improve apparent color strength and edge definition, but retained pigment still needs sufficient protection after curing. In a study of pigment inkjet printing on cotton and polyester, Ding and colleagues associated low crockfastness in the investigated pretreated samples with higher surface pigment levels. That finding explains a possible trade-off; it does not mean that all pretreatments reduce fastness. [3]

Excessive or uneven dry deposition

A concentrated bath does not directly describe the amount remaining on fabric. Application pickup and distribution also matter. Where compatible measurement methods are available, compare dry add-on or another validated deposition indicator, not concentration alone. Record whether the fabric was padded, sprayed or otherwise treated, because the same bath can produce different surface distributions.

Overapplication may change hand, drying demand and the balance of the surface layer. Underapplication may produce poor immobilization or inconsistent coverage. Either can coexist with a visually attractive sample. Map the issue across the width and through the run before deciding that the formulation itself is unsuitable.

Compatibility must be judged in the intended process

Some pretreatment systems deliberately immobilize ink through an interaction at the textile surface. Therefore, mixing concentrated ink and pretreatment in a cup and expecting indefinite stability is not a reliable simulation of printing. Evaluate the actual sequence, dilution, application and drying conditions recommended for the system.

At the same time, uncontrolled instability in the pretreatment bath is a different issue. Water quality, unauthorized additives, carryover and storage conditions should be checked when appearance or application behavior changes. Keep records of preparation order and material lots so that a formulation question can be separated from a handling problem.

Do not use viscosity as a substitute for finished-fabric testing

Two products can show similar viscosity while differing in composition, wetting, deposition, color development and final hand. A purchasing comparison based only on viscosity or price per kilogram can therefore select a product that costs more per accepted meter. The relevant comparison is the complete printed and cured result at a controlled application level.

Fabric structure also matters. Research on digitally printed polyester has examined the relationship between fabric surface characteristics and printing quality. Treat construction as a trial variable when changing fabric, not as an invisible constant behind a chemical comparison. [8]

Curing-Related Causes: A Dry Print May Still Be Inadequately Fixed

Drying removes liquid; curing develops the final properties required by the binder system. These functions may occur in the same equipment, but a dry touch does not establish adequate film formation or any chemistry-dependent crosslinking. Use the supplier’s validated process as the starting window, then verify performance on the actual fabric and production line.

Check exposure at the fabric, not only the controller

The set temperature is an equipment setting. The printed fabric has its own heating history, affected by incoming moisture, fabric mass, loading, airflow and transport conditions. Total time inside a dryer is not necessarily the time spent at the temperature needed for the approved curing process.

Brother’s GTXpro guide calls for checking actual curing temperature with a probe or temperature strips for its specified system. That supports verifying exposure rather than relying only on a controller setting. For a wider line, plan representative measurement locations according to the equipment and process; this sampling recommendation is not an additional claim from that guide. Distinguish an air reading from the printed textile’s temperature and do not transfer Brother’s numerical settings to an unrelated ink system. Brother GTXpro Daily Operations Guide

Use a controlled recure as a diagnostic clue

Compare a retained failing specimen with a counterpart given an additional, supplier-approved thermal treatment within fabric limitations. Improvement suggests that thermal exposure or subsequent film development deserves investigation. It does not prove that the original failure had only one cause, and it does not establish that the recured article meets all other requirements.

If the recure does not improve wet rubbing, do not keep adding heat indefinitely. Review surface deposition, compatibility and substrate transfer. If it improves rubbing but creates yellowing, shade change, shrinkage or unacceptable hand, it is not a usable correction. The production target is an acceptable thermal window, not the highest possible temperature.

Explain why laboratory success disappears on the line

A small specimen may heat differently from a wide, heavily printed fabric under production loading. Start-up conditions and changes in incoming moisture can also matter. Repeat thermal checks with representative coverage, width and loading. Link each rubbing result to the corresponding process record instead of assuming that one calibration describes every production condition.

Use the Failure Pattern to Choose the Next Check

The following matrix prioritizes investigations. Each row describes a clue rather than a confirmed diagnosis. Several causes may operate together, so use the simplest discriminating check before changing several variables.

Dark-area failure deserves careful interpretation. Increasing the laydown of a formulated ink can increase both pigment and its accompanying binder; it does not automatically change their formulation ratio. Nevertheless, the thicker deposited assembly and its interaction with pretreatment can behave differently. Avoid describing every coverage-related failure as “too much pigment and too little binder” without supporting evidence.

Where white underbase is used, record the complete layer sequence and coverage. The interface between layers, the total deposit and the relevant processing steps become part of the investigation. A result from a color-only print on white fabric cannot establish performance for the layered print on a dark garment.

Run Controlled Trials That Can Identify a Cause

A useful trial separates causal screening from final shade matching. In the first stage, hold the artwork, print settings, fabric and assessment conditions constant while changing one defined factor. In the second stage, optimize the promising route to the required shade and complete specification. Otherwise, a lighter trial can appear more durable simply because less color is available for transfer.

1. Retain the baseline. Preserve failing production fabric, the matching blank and a passing reference where available.
2. Reproduce the failure. Align the test method and confirm that the problem exceeds ordinary specimen variation.
3. Verify process records. Check material lots, deposition, print coverage and measured thermal conditions.
4. Select one leading hypothesis. Use the observed failure pattern to choose the first variable.
5. Run bounded comparisons. Stay within supplier-approved material and processing limits, with repeat specimens.
6. Evaluate the whole result. Measure rubbing alongside shade, hand and required laundering behavior.
7. Confirm on the line. Reproduce the chosen route across relevant positions and production conditions.

One-factor screening is a practical first step, but interactions may require a structured follow-up. For example, changing pretreatment deposition can also change the thermal demand. If a result is ambiguous, use a small planned experiment that separates deposition and curing effects. Do not interpret a simultaneous chemical and dryer change as proof that either change alone solved the problem.

Define repeat sampling according to production variability and the buyer’s requirements. Record individual grades, specimen positions and any borderline result. A single improved cutting is evidence for the next trial, not sufficient evidence for unrestricted production approval.

Improve Wet Rubbing Without Losing Color Yield or Softness

The best correction is the smallest verified change that brings the finished product inside every required limit. Adding polymer until the surface becomes rigid may improve one result while making the fabric commercially unacceptable. Reducing ink until rubbing passes may fail the shade target. Neither is a balanced solution.

Do not automatically add a softener to compensate for a stiff correction. A finishing additive may change friction, wetting or compatibility, and its effect depends on the entire system. Revalidate fastness after the proposed finish rather than assuming that a softer touch confirms an improved product.

Use an agreed physical hand reference, consistent sample conditioning and a repeatable panel or instrumental procedure appropriate to the product. Compare unprinted, treated-only and printed fabric so that the source of stiffness is visible. For dense prints, include both the printed area and the transition to unprinted fabric.

Likewise, do not prescribe a reactive-style wash-off or disperse reduction-clearing process as a generic cure for pigment transfer. Follow the pigment system’s intended finishing route. A system that does not require production wash-off still needs the end-use laundering and rubbing tests specified for the finished article.

Approve a Repeatable Production Window and Compare Total Cost

Once a promising correction is identified, document an operating window rather than one successful machine setting. Include the approved substrate range, material identity, application controls, print coverage limits, thermal verification and release tests. Recheck the window when a meaningful change occurs, such as a new fabric finish, ink set or dryer loading pattern.

For a practical total cost indicator, compare the same cost boundary for every candidate:

Total cost per accepted meter = included production costs ÷ meters meeting the complete finished-fabric specification.

Included costs may cover pretreatment, ink, other approved finishes, energy, relevant labor, rework and rejects. Define the boundary consistently and avoid counting rejected material twice. For garment printing, use accepted garments instead of meters.

A lower-priced pretreatment can become more expensive if it requires higher application, slower curing or more rework. Conversely, a higher-priced material needs evidence of an economic benefit rather than a claim based on nominal concentration. Compare measured consumption and saleable output at equivalent shade, hand and fastness requirements.

Release criteria should also address variability. If the mean result improves but the weakest width position still fails, the process is not adequately controlled. Use the trial data to decide which variables need routine monitoring and which changes require renewed approval.

Ko'p beriladigan savollar

1. Why does a pigment print pass dry rubbing but fail wet rubbing?

Water changes the conditions under which the deposited layer and textile resist friction. A surface can perform adequately when dry yet release color-bearing material when wet. Check test consistency, film behavior, adhesion, residual components and substrate transfer before selecting a correction.

2. Does poor wet rubbing always mean insufficient binder?

No. Similar failures can arise from incomplete curing, uneven pretreatment, exposed surface pigment, incompatible materials or the base fabric. Binder quantity should be investigated within the complete system rather than treated as the default cause.

3. Will more pretreatment improve wet rubbing fastness?

Not necessarily. More pretreatment may improve color retention while also changing surface pigment distribution and deposited solids. Compare controlled application levels and evaluate the cured result for rubbing, shade, hand and uniformity.

4. Is pretreatment solids content the same as binder content?

No. Total solids include the nonvolatile components measured by the relevant procedure, which may serve several functions. Solids content alone does not identify the effective binder contribution or predict wet rubbing performance.

5. Can higher curing temperature solve the problem?

It can help when insufficient thermal exposure is a contributing cause, provided the change remains within approved limits. It cannot reliably correct an unsuitable material combination or background fabric transfer, and excessive exposure can compromise appearance or hand.

6. Why are dark, high-coverage prints more difficult?

They can present a larger deposited load and different drying or interlayer demands. A coverage ladder helps reveal the limitation. More ink does not automatically mean a lower binder-to-pigment ratio within a formulated ink.

7. Can a softener improve wet rubbing?

Its effect is system-dependent. A change in surface friction may be useful, but compatibility and durability can also change. Use only an approved finishing option and repeat the complete fastness and hand evaluation.

8. Should pigment prints be washed before rubbing tests?

Follow the buyer’s specification and selected method. Testing before washing, after specified laundering or at both stages answers different questions. Do not add a wash simply to obtain a more favorable grade.

9. Can cotton and polyester blends use the same correction?

Only after validation. Composition, construction and finish affect deposition and adhesion. A successful adjustment on one fabric is a useful trial starting point, not automatic approval for another substrate.

10. What wet rubbing grade should pigment printing achieve?

The required grade depends on the buyer, end use, test method and agreed condition of the specimen. Establish that requirement before trials. There is no single acceptance grade suitable for every pigment-printed textile.

11. Can laboratory results predict production performance?

They help screen causes and materials, but production introduces width, loading and application variation. Confirm the selected route on representative equipment and inspect results from relevant positions and operating conditions.

12. What information should be sent to a chemical supplier?

Provide the substrate, ink system, pretreatment route, application records, print coverage, thermal data, test method, failing grade and target requirements. Include retained samples and blank controls when practical. This makes a matched trial more informative than a request for a stronger binder alone.

Plan a Matched-System Evaluation with FSX Chemical

When wet rubbing is poor, begin with evidence from the failing print. FSX Chemical’s sample matching service provides a starting point for discussing a pretreatment evaluation against your fabric, printing route and finished-product targets.

Review the digital printing paste range, including the DP-P pigment-printing trial route, and share the actual process conditions before selecting a candidate. Product selection should lead to a controlled trial; it is not a guarantee of a particular rubbing grade on every ink and substrate combination.

FSX Chemical bilan bog'laning with your wet rubbing report, fabric specification, existing pretreatment procedure and curing record. Request a comparison that evaluates color yield, wet and dry rubbing, hand, required washing performance and total cost per accepted output.📧 Elektron pochtaService@fsxchemical.com