Khắc phục sự cố liên quan đến bột in trên vải: Nguyên nhân, phương pháp kiểm tra và biện pháp khắc phục

Textile printing paste problems rarely have one cause. Diagnose the symptom by checking product identity, preparation, temperature, viscosity method, formulation additions, holding time, machine conditions, fabric and post-treatment. Change one controlled variable at a time before replacing the thickener.

Identify the material being diagnosed: a dye-screen paste, a pigment-binder screen paste, or a fabric-applied digital pretreatment. Their chemistry, application and after-treatment differ. Record the dye or ink system, fibre and product-addition position before testing. A fabric pretreatment or conventional screen thickener is not automatically suitable for addition to printhead ink; diagnose that ink system under its own supplier-approved requirements.

This is why textile printing problems should not be corrected by changing the thickener immediately. A paste that appears too thin may be caused by incorrect concentration, high temperature, incomplete hydration, electrolyte interaction or an incorrect viscosity test method. A blurred print may come from paste rheology, but it may also come from excessive application, absorbent fabric or unsuitable machine settings.

Effective troubleshooting begins by defining the symptom, collecting process data and changing one variable at a time. The objective is to identify the real root cause before modifying the formulation.

The following guide provides a practical troubleshooting framework for reactive, disperse, pigment and digital textile printing paste systems.

Why Printing Paste Problems Require Systematic Diagnosis

Textile printing paste performance is affected by several groups of variables at the same time. A visible defect on the fabric is often the final result of interactions that started much earlier in the process.

Raw-material variables

Thickener grade, polymer concentration, moisture, particle profile, batch variation and storage conditions can influence paste preparation and rheology.

Preparation variables

Water quality, powder-addition rate, mixer geometry, mixing speed, hydration time, temperature and order of chemical addition can all change the final paste.

Formulation variables

Dyes, pigments, salts, alkalis, binders, crosslinkers, humectants, surfactants and other polymers can change viscosity and physical stability.

Machine variables

Pumping, circulation, screen condition, squeegee pressure, printing speed, coating gap and application quantity influence how the paste reaches the textile.

Fabric variables

Fibre composition, fabric weight, construction, absorbency and previous finishing treatments influence spreading and penetration.

Post-treatment variables

Drying, steaming, thermofixation, curing and washing can change shade, definition and fabric handle after printing.

Troubleshooting should therefore begin with the complete process rather than with one material in isolation.

Start with Five Basic Checks

Locate the first point where the questioned material differs from a retained approved control: prepared thickener base/stock, complete paste, freshly printed fabric, or finished fabric. Compare under the same preparation, measurement and machine conditions. For dye printing, retain checkpoints after the specified fixation and wash-off; for pigment printing, evaluate after the validated cure and conditioning. For digital fabric pretreatment, hold ink and print settings fixed when comparing treated fabrics. Use the five checks below to isolate the difference, then change only a variable compatible with that route.

1. Confirm the correct product

Check the commercial product code, batch number, package label and current TDS. Make sure the material used in production is the same grade that was approved during testing.

2. Confirm the preparation method

Check concentration, water quantity, powder addition, mixing speed, hydration time and order of chemical addition.

3. Confirm temperature

A viscosity difference may be caused by sample temperature rather than a real formulation change.

4. Confirm the viscosity test method

Record instrument model and torque range, spindle or geometry, speed, container/sample volume, concentration basis, temperature, preparation/rest history and reading time before comparing results. Record torque as well as viscosity, and follow the instrument’s valid range. Brookfield’s viscosity guidance explains why spindle and speed selection matter; changing either can change the apparent viscosity of a non-Newtonian paste.

5. Compare with a retained reference

Where available, prepare a retained sample of the approved product using exactly the same method as the current batch.

1. Lumps and Fish Eyes in the Printing Paste

Lumps are common when powdered thickeners hydrate rapidly at the surface before water reaches the inside of the particle cluster.

Possible causes

• Powder added too quickly
• Insufficient water circulation before addition
• Powder added into one location
• Unsuitable mixer or impeller position
• Incorrect water temperature
• Insufficient hydration time
• Moisture-damaged or compacted powder

Recommended checks

Prepare a fresh laboratory batch while recording powder-addition time and mixing conditions. Add the thickener gradually into a properly circulating water phase and inspect the paste before and after the defined hydration period.

Do not simply increase mixing time

Persistent lumps may contain dry polymer surrounded by a hydrated outer layer. Additional mixing does not always eliminate them efficiently.

When comparing alginat natri, CMC hoặc CMS, the preparation method should be appropriate for the specific grade.

2. Printing Paste Viscosity Is Too Low

Low viscosity does not automatically mean that more thickener should be added.

Possible causes

• Incorrect weighing or excessive water
• Incomplete polymer hydration
• Sample temperature above the reference condition
• Incorrect product grade
• Different viscosity measurement method
• Salt, alkali or another electrolyte reducing viscosity
• Prolonged shear in a sensitive system
• Microbiological or chemical degradation in stored paste

Recommended checks

Verify batch weights first. Then confirm temperature, hydration time and viscosity method. If the stock paste is correct but the complete color paste becomes thin, investigate the formulation rather than immediately increasing polymer dosage.

Correct carefully

Adding dry thickener directly to a completed color paste can create lumps and local concentration differences. Any correction procedure should be validated for the specific product and formulation.

3. Printing Paste Viscosity Is Too High

Excessive viscosity can reduce screen transfer, create pumping resistance and produce uneven solid areas.

Possible causes

• Excess thickener dosage
• Incorrect total batch weight
• Water evaporation
• Lower measurement temperature
• Continued hydration after the first test
• Incorrect grade used in production
• Different measurement speed or spindle

Check before adding water

Confirm the sample temperature and test method. If evaporation is the cause, identify why the tank or container is losing water.

Why uncontrolled dilution is risky

Adding water changes not only viscosity but also the concentration of dyes, salts, binders, alkalis and other auxiliaries. The corrected paste may reach the target viscosity while no longer matching the approved formulation.

4. Viscosity Changes During Holding

A paste may be within specification immediately after preparation and move outside the operating window several hours later.

Viscosity increases may be caused by

• Continued polymer hydration
• Evaporation
• Temperature decrease
• Delayed interaction between formulation components

Viscosity decreases may be caused by

• Temperature increase
• Electrolyte interaction
• pH change
• Prolonged mechanical shear
• Polymer incompatibility
• Contamination or degradation

Recommended approach

Take representative aliquots at defined production checkpoints and keep them covered to limit evaporation. Condition each to the same test temperature and apply the same rest and reading sequence. Record apparent viscosity, pH, sample temperature, preparation time, appearance and separation together. If a circulating paste reads lower, compare it after a defined recovery period with a matched held control before calling the loss permanent degradation. Recovery of one reading does not prove the paste is suitable for continued production.

A numerical change is most important when it also changes machine behavior or finished-fabric performance.

5. Viscosity Changes After Adding Salt, Alkali or Auxiliaries

Many printing thickeners are sensitive to ionic strength, pH and local chemical concentration.

Possible causes

• Electrolyte interaction with the polymer
• Rapid local pH change
• Highly concentrated chemical added directly
• Incorrect addition sequence
• Incompatible polymers or auxiliaries

Use staged testing

Prepare the thickener paste first, then add formulation components one at a time while measuring viscosity and observing appearance.

Identify the critical addition

When the viscosity changes sharply after one component is introduced, investigate its concentration, dilution and addition sequence before changing the thickener.

Application chemistry matters

A product suitable for one reactive, disperse or pigment formula may behave differently under another chemical load.

6. Excessive Filter Residue or Poor Screen Passage

Filter residue can interfere with screens, pumps and continuous production. However, its origin should be identified before blaming raw material purity.

Possible sources of residue

• Incompletely hydrated thickener
• Powder lumps
• Hydrated gel particles
• Chemical precipitation
• Polymer incompatibility
• Fibres from bags or fabric
• Dirty tanks or pipelines
• Foreign particles from production equipment

Test the stock paste first

If the stock thickener paste filters well but the complete formulation does not, the problem probably develops after another chemical is added.

Inspect the residue

Dry or examine the retained material where practical. The appearance of the residue can help distinguish polymer gel from foreign contamination or chemical precipitation.

Standardize filtration

Record filter material, opening size, sample quantity, pressure condition and time so that results remain comparable.

7. Excessive Foam and Entrapped Air

Foam can produce inaccurate viscosity readings, poor transfer, pinholes and uneven printed areas.

Possible causes

• Mixer pulling air into the batch
• Excessive mixing speed
• Surfactant-containing auxiliaries
• Air entering through pump seals or return lines
• Incorrect tank level or circulation pattern

Observe when foam begins

If foam starts during water and thickener preparation, review mixing. If it appears only after an auxiliary is added, review that component.

Measure foam decay

Initial foam volume and the time required for bubbles to disappear can both be useful.

Do not automatically increase defoamer

Defoamer can influence wetting, coating and printing behavior. Correct the mechanical cause first where possible.

8. Paste Separation, Settling or Syneresis

A printing paste should remain sufficiently uniform during its approved holding and production period.

Possible causes

• Insufficient rheological structure
• Incompatible thickener and formulation components
• Incorrect pH
• High electrolyte load
• Poor pigment or dye dispersion
• Incorrect solids concentration
• Storage beyond the validated holding period

Inspect the type of separation

Clear liquid at the surface, dense sediment at the bottom and visible gel phases can indicate different mechanisms.

Do not rely only on remixing

A paste that temporarily returns to a uniform appearance after stirring may still be fundamentally unstable.

Print fresh and stored paste

Compare fabric results to determine whether the physical change affects application quality.

9. Poor Paste Transfer

A paste may have acceptable standing viscosity but fail to transfer completely through the printing equipment.

Possible causes

• Viscosity too high
• Unsuitable shear-thinning behavior
• Excessive structural recovery
• Screen or mesh too restrictive
• Low squeegee pressure
• Insufficient paste supply
• Filter or screen contamination

Do not judge from standing viscosity alone

Compare viscosity at multiple speeds or use application-relevant rheology data when possible.

Check the machine before reformulating

Screen condition, squeegee settings and paste level can create symptoms that resemble excessive viscosity.

10. Printed Edges Spread or Lose Definition

Edge spreading is one of the most common reasons printing mills consider changing their thickener.

Possible paste-related causes

• Viscosity below the practical operating range
• Weak structural recovery after shear
• Excessive water or humectant
• Excessive paste application

Possible fabric-related causes

• High absorbency
• Open fabric construction
• Inconsistent pretreatment
• Residual wetting or finishing chemicals

Possible process-related causes

• Excessive pressure
• Slow drying
• Incorrect screen conditions
• Uncontrolled moisture before fixation

Increasing viscosity may reduce spreading in some cases, but excessive viscosity can create poor transfer and broken fine lines. Rheology, application quantity and fabric absorbency should be reviewed together.

11. Fine Lines Break or Small Details Disappear

Broken lines are not always the opposite of edge spreading. The paste can be too structured to transfer through fine design elements.

Possible causes

• Viscosity too high
• Poor flow under shear
• Filter residue or gel particles
• Tình trạng màn hình bị che khuất
• Insufficient application pressure
• Insufficient paste supply
• Unsuitable fabric surface

Use a diagnostic test pattern

Include several line widths, small text and dots. This makes it easier to determine the point at which detail begins to fail.

Compare screen and paste together

If the same paste works through a more open screen, investigate filtration and rheology before changing total viscosity.

12. Large Solid Areas Print Unevenly

A formulation can reproduce fine lines but still perform poorly in large solid areas.

Possible causes

• Poor leveling
• Excessive paste structure
• Foam or entrapped air
• Uneven screen transfer
• Variable fabric absorbency
• Insufficient paste supply
• Uneven squeegee or roller pressure

Check dark shades

Black, navy and other deep shades often reveal levelness and transfer differences more clearly than light colors.

Check across the fabric width

A left-to-right difference may indicate mechanical or fabric variation rather than the thickener itself.

13. Excessive Fabric Penetration or Strike-Through

Too much paste moving through the fabric can reduce surface color concentration and create reverse-side contamination.

Possible causes

• Low paste structure
• Excessive application quantity
• High machine pressure
• Lightweight or open fabric
• High fabric absorbency
• Unsuitable wetting behavior

Inspect both sides of the textile

Compare surface coverage and back penetration using the same fabric lot and print conditions.

Avoid correcting fabric problems only with viscosity

Extremely high viscosity may reduce penetration but create poor transfer. Application quantity and machine settings should also be optimized.

14. Color Becomes Weak After Fixation or Washing

When the wet or dried print looks strong but color becomes weak after fixation or washing, the thickener may not be the primary cause.

Possible causes

• Incorrect dye or pigment concentration
• Excessive penetration into the fabric
• Insufficient alkali or fixation chemistry
• Incorrect steaming or curing conditions
• Reactive dye hydrolysis
• Binder-film failure in pigment printing
• An after-treatment route that does not match the dye, fibre or binder specification

Check fixation before changing the thickener

Temperature, moisture, dwell time and chemical conditions should be recorded.

Compare identical post-treatment

Candidate and reference thickener systems must use the same fixation and washing conditions.

15. Difficult Wash-Off or Stiff Fabric Handle

First separate a removable dye-printing paste residue from the binder film intended to remain in a pigment print. Stiff hand can occur in both routes, but the corrective actions differ. Do not use stronger washing as a general remedy for a pigment film or reduce dye-print wash-off solely to retain shade.

Possible causes

• Excessive thickener dosage
• High paste pickup
• Thickener route with unsuitable removal behavior
• Insufficient washing
• Excessive binder deposition
• Incorrect curing conditions

Evaluate after complete finishing

Fabric handle should not be judged from the freshly printed material.

Compare printed and unprinted areas

This helps determine whether stiffness is related to paste deposition or the fabric finishing process.

Consider total polymer solids

For a dye-printing route, compare residual paste after the specified fixation and wash-off; investigate grade suitability, add-on and washing together. For pigment printing, compare cured hand at recorded paste deposit, binder dose and documented nonvolatile addition, then check the approved cure and fastness. A heavier cured deposit does not identify which polymer caused stiffness, and nonvolatile content does not selectively measure active thickener polymer.

16. Laboratory Results Are Good but Production Fails

Scale-up differences are one of the most important causes of failed thickener evaluations.

Laboratory and production differ in

• Tank geometry
• Impeller design
• Batch volume
• Mixing circulation
• Heat generation
• Thời gian bù nước
• Pump and pipeline shear
• Thời gian giữ
• Fabric quantity and variation

Do not copy mixer RPM directly

The same rotational speed in a small laboratory mixer and a production tank does not create the same flow pattern.

Conduct a controlled scale-up

Preserve concentration, addition sequence and QC method while adjusting mixing parameters appropriately for production equipment.

Monitor the entire production run

Compare fabric from the beginning, middle and end rather than approving only the first metres.

17. Approved Sample and Bulk Batch Perform Differently

A successful laboratory sample must be connected to a controlled commercial product and manufacturing batch.

Check product identity

Compare the sample code, commercial grade, purchase order, package label and batch COA.

Check incoming test conditions

Verify whether the original sample and bulk product were prepared using the same concentration, water, hydration and viscosity method.

Check storage and transport

Moisture exposure, damaged packaging or inappropriate storage can change the condition of some thickener products.

Use retained samples

Prepare the approved retained sample and the questioned production batch side by side under identical conditions.

Verify the first commercial batch

First-batch verification reduces the risk of moving directly from a small sample to unrestricted production.

Troubleshooting by Printing Route

Lộ trình in ấn	Common Paste Issues	Priority Checks
In lụa phản ứng	Viscosity drift, spreading, filtration, weak color after wash-off	Thickener hydration, alkali and salt compatibility, fabric, steaming and wash-off
Disperse printing	Paste instability, uneven transfer, poor solid areas, surface residue	Thickener route, dye dispersion, rheology, polyester surface and fixation
Pigment printing	Binder instability, poor definition, stiff handle and weak rubbing performance	Thickener-binder compatibility, solids, curing and film formation
Reactive digital pretreatment	Uneven pickup, ink spreading, viscosity drift and difficult wash-off	Pretreatment rheology, fabric absorbency, chemical distribution and fixation
Disperse digital pretreatment	Uneven application, filtration problems and inconsistent color	Polyester preparation, paste stability, coating uniformity and thermal process
Pigment digital pretreatment	Spreading, binder interaction, stiff handle and uneven solids	Binder compatibility, pickup, rheology, drying and curing

Digital printing should use an application-specific hỗn hợp in kỹ thuật số or validated pretreatment route rather than transferring a conventional screen-printing paste directly.

A Practical Root-Cause Troubleshooting Workflow

Step 1: Describe the symptom precisely

Replace general statements such as “the paste is bad” with measurable observations such as “viscosity decreases after alkali addition” or “black fine lines spread after 30 minutes of holding.”

Step 2: Identify when the problem first appears

Determine whether the problem starts during powder preparation, chemical addition, holding, circulation, printing, fixation or washing.

Step 3: Compare with the approved reference

Prepare current and reference products side by side using identical conditions.

Step 4: Separate material and process variables

Use the same batch of fabric and chemicals where possible while changing only one suspected variable.

Step 5: Test the stock paste

Check hydration, viscosity, filtration, foam and appearance before adding dyes or other chemicals.

Step 6: Add formulation components in stages

This helps identify whether the problem begins after salt, alkali, binder or another auxiliary is introduced.

Step 7: Test fresh and held paste

Compare immediately after preparation and after a production-relevant holding period.

Step 8: Complete the fabric test

Evaluate definition, penetration, color uniformity and surface condition.

Step 9: Complete fixation and post-treatment

Do not make the final decision from the wet print alone.

Step 10: Conduct a limited production trial

Confirm performance under realistic tank size, circulation, speed and production time before changing bulk supply.

What Data Should Be Recorded Before Adjusting the Paste?

Good troubleshooting depends on good records. Before changing the formulation, collect enough information to reconstruct the batch.

Thickener information

• Product and grade
• Batch number
• TDS and recent COA where available
• Liều lượng
• Powder or liquid condition

Preparation information

• Total batch size
• Nguồn nước
• Water temperature
• Mixing equipment
• Powder-addition time
• Mixing duration
• Thời gian bù nước
• Thứ tự cộng

QC information

• Viscosity and complete measurement method
• pH
• Lọc
• Hình thức
• Bọt
• Holding-time results

Printing information

• Fabric composition and weight
• Printing equipment
• Screen or application conditions
• Tốc độ sản xuất
• Paste application quantity where available
• Fixation or curing conditions
• Wash-off process

Defect information

• Photographs
• Printed fabric sample
• Paste sample
• Time when the defect first appeared
• Whether the defect is continuous or intermittent

When Should You Change the Thickener?

Changing the thickener is appropriate when controlled testing shows that the current polymer route cannot meet the required combination of viscosity, rheology, stability, filtration and finished-fabric quality.

Consider a different grade when

• The current viscosity range is unsuitable for the equipment
• Hydration is consistently incompatible with the production process
• Filtration remains unacceptable under controlled preparation
• Chemical compatibility is insufficient
• Rheology produces poor transfer or excessive spreading
• Holding stability does not meet production requirements
• Batch consistency cannot be controlled satisfactorily

Consider a different thickener family when

The application chemistry itself is better suited to another polymer route. For example, conventional reactive printing may begin with alginat natri , while selected disperse or compound systems may evaluate CMS , and selected printing or rheology applications may evaluate CMC .

Do not change products without a reference trial

A candidate product should be compared with the current grade under the same laboratory and production conditions before commercial conversion. For a conventional pigment-screen paste, use staged synthetic thickener production approval tests after the cause is isolated, rather than treating a viscosity correction as full product approval.

Các câu hỏi thường gặp

What should be checked first when a printing paste suddenly changes?

Confirm the product and batch, preparation record, water, temperature, hydration time, viscosity method and addition sequence. Compare the result with an identified retained sample before changing the formula.

Why can viscosity be correct while print definition is poor?

One viscosity number does not describe shear response, recovery, paste transfer, fabric absorbency or pickup. Review multi-speed behavior and the complete printing process.

How should lumps or fish eyes be investigated?

Check powder-addition rate, agitation pattern, wetting, hydration time, water quality and filtration residue. Excess mixing after lumps form may introduce air without correcting the wetting failure.

What causes viscosity to change after salt, alkali or auxiliaries are added?

Electrolytes, pH, addition order, local concentration and polymer compatibility can alter thickener structure. Add components in controlled stages and measure after each stage.

When should a mill test a different thickener grade?

Test an alternative only after the method and root-cause checks are controlled, or when the existing grade cannot meet the complete-paste, machine and finished-fabric requirements within a practical operating window.

How FSX Chemical Supports Printing Paste Troubleshooting

FSX Chemical supplies sodium alginate, CMC, CMS, digital printing paste and related textile thickener routes for printing mills, formulators, importers and distributors.

Troubleshooting begins with the customer’s actual process rather than with an assumption that the thickener must be replaced.

Buyers can provide

• Current thickener or printing paste name and grade
• TDS, SDS hoặc COA hiện tại
• Physical powder or paste sample
• Độ nhớt và phương pháp thử nghiệm toàn diện
• Công thức hoàn chỉnh
• Quy trình chuẩn bị và cấp nước
• Fabric composition and construction
• Reactive, disperse, pigment or digital route
• Printing equipment and production speed
• Filtration or stability records
• Defect photographs or printed fabric samples

Technical review may include

• Review of the existing product and test method
• Identification of likely root-cause categories
• Alignment of viscosity and preparation procedures
• Review of chemical compatibility
• Selection of an appropriate candidate product family
• Provision of relevant TDS and SDS information
• Representative sample support
• Guidance for controlled side-by-side testing
• Review of laboratory and production feedback
• First commercial batch verification planning

Buyers can submit an existing paste, thickener or TDS through Mẫu hóa chất FSX và việc so sánh 📧 Email: Service@fsxchemical.com

A candidate product remains subject to controlled laboratory and production evaluation. Final suitability depends on the complete formulation, fabric, equipment and post-treatment process.