What Is the Sizing Process?
Sizing is the application of a protective coating (starch, PVA, acrylics, blends) to warp yarns to:
Increase tensile strength
Reduce hairiness
Lower abrasion during weaving
Improve loom efficiency
Enhance fabric quality
This step is essential because warp yarns endure significant stress during shedding, picking, and beating-up. Without sizing, spun yarns-especially cotton and viscose-would break excessively.
Alpenol formulations are designed to deliver strong adhesion and flexible films, helping mills reach high weaving speeds with reduced warp breaks.
To learn more about the sizing process, click here.
What Is the Machine Flow of the Sizing Process?
The typical sizing machine (slasher or multi-box) follows this sequential flow:
1. Creel / Warp Supply
Warp ends arranged parallel on beams
Tension equalized
Broken ends repaired
2. Size Box (Impregnation Zone)
Yarn sheet immersed in size formulation
Key variables: viscosity, temperature, penetration, wetting
3. Squeeze / Nip Rollers
Remove excess size
Control pick-up
Prevent dripping and uneven coating
4. Drying Zone
Multi-cylinder drying
Removes moisture, sets the film
Influences flexibility, brittleness, and sticking
5. Leasing & Separation
Warp threads grouped correctly
Prevents sticking and entanglement
6. Re-Beaming
Warp rewound onto a weaving beam
Tension must be uniform
Beam quality critical for loom stability
Throughout this process, QC teams monitor checkpoints to maintain consistent results.
What Are Common Defects in Sizing?
Sizing Defect | Cause | Impact |
Uneven pick-up | Viscosity drift, roller pressure imbalance | Bar lines, irregular yarn strength |
Flaking/powdering | Brittle film, over-drying | Dust, loom stoppages |
Sticking | Under-drying, excess plasticizer | Reed marks, poor shedding |
Poor penetration | High viscosity, inadequate wetting | Hairiness, weak film |
Lumps/gels | Improper cooking or mixing | Roller deposits, streaks |
High hairiness | Under-sizing | Excessive abrasion on loom |
Alpenol systems reduce many of these issues by maintaining stable viscosity and providing enhanced flexibility in the size film.
To learn more about the defects in sizing, click here.
What Are the Checkpoints of the Sizing Process?
Sizing QC checkpoints are divided into pre-sizing, in-process, and post-sizing stages. Each checkpoint ensures consistency, minimizes defects, and optimizes loom performance.
1. Pre-Sizing Checkpoints
A. Yarn Quality Check
Yarn count
Strength
Hairiness
Moisture content
Blend ratio
Why it matters: The sizing recipe and penetration depth must match yarn characteristics. For example, highly hairy cotton yarns require more adhesion and smoother films-achieved easily with Alpenol’s high-cohesion agents.
B. Recipe Verification
Solid content
Polymer ratios (starch/PVA/acrylic)
Additive levels
pH control
Why it matters: Incorrect recipes lead to brittle film, sticking, or poor penetration.
C. Size Bath Preparation
Proper cooking of starch
Even blending of all polymers
No lumps/gels
Temperature control
Why it matters: A homogeneous bath ensures uniform film on warp ends.
2. In-Process Checkpoints
A. Viscosity Monitoring
Checked every 1–2 hours
Must remain within specified range
Why it matters: Viscosity drift = uneven pick-up → inconsistent warp performance.
B. Size Pick-Up Measurement
Adjusted through nip pressure & immersion level
Should be uniform across warp width
Why it matters: Too much pick-up → brittleness
Too little → insufficient protection
C. Squeeze Roller Pressure
Uniform pressure across roll width
Surface clean & parallel alignment
Why it matters: Imbalanced pressure causes streaks and side-centre variation.
D. Warp Sheet Tension
Should remain steady across the process
No loose or overtight ends
Why it matters: Tension variations create uneven penetration and inconsistent drying.
E. Drying Temperature Control
Balanced cylinder temperature profile
Target moisture regain at take-up
Why it matters:
Over-drying → brittle film + flaking
Under-drying → sticky yarn
Flexible-film chemistries like Alpenol maintain strength even with slight moisture variations.
F. Yarn Separation at Leasing Rods
Prevent sticking
Maintain sheet uniformity
G. End-Break Frequency
Monitored throughout the run
Why it matters: Rising break rates indicate immediate sizing issues.
3. Post-Sizing Checkpoints
A. Yarn Strength & Elongation Test
Tensile strength should increase by 15–25%
Check both edge and center ends
B. Hairiness Measurement
Expect noticeable reduction
Use USTER hairiness index or equivalent
C. Film Uniformity Evaluation
No cracks, flaking, or powdering
Film should flex without breaking
D. Moisture Content Check
Typically 6–12% depending on yarn type
E. Beam Build Quality
Even tension
Smooth winding
No ridges or slack ends
Why it matters: Poor beam quality leads to loom stoppages-even when size quality is good.
F. Loom Trial
Low warp breakage
Low dust levels
Stable running at target loom speed
Warp beams sized with Alpenol often show improved loom efficiency due to the consistent and flexible film.
Why Are These Checkpoints Important?
1. Ensure Yarn Strength & Protection
Sizing protects yarn from mechanical stress during weaving.
2. Maintain Fabric Quality
Prevents streakiness, reed marks, and uneven texture.
3. Optimize Production Efficiency
Reduces loom stoppages and maintenance downtime.
4. Improve Cost-Efficiency
Correct pick-up avoids overuse of size chemicals.
(Alpenol’s lower add-on requirement enhances cost savings.)
5. Ensure Lot-to-Lot Consistency
Stable QC checkpoints prevent variability in quality or performance.
6. Reduce Environmental Impact
Controlled sizing reduces chemical load in wastewater.
Alpenol’s high-efficiency systems further reduce solids consumption.
FAQs
1. What is the sizing process?
It is the application of a protective polymer film to warp yarns to improve weaving performance.
2. What are the main checkpoints in sizing?
Yarn inspection, recipe control, viscosity monitoring, pick-up consistency, drying control, strength testing, and loom trials.
3. Why are checkpoints important?
They ensure stable weaving, reduce defects, and maintain consistent quality.
4. What are common defects in sizing?
Uneven pick-up, flaking, sticking, low penetration, high hairiness, and roller build-up.
5. How does sizing chemistry affect QC?
Stable and flexible-film systems like Alpenol reduce brittleness, improve adhesion, and make QC checkpoints easier to maintain.
References
PMC: Cotton Warp Sizing Evaluation (Viscosity/Pick-Up QC),
https://pmc.ncbi.nlm.nih.gov/articles/PMC12845530/
TextileTrainer: Sizing Ingredients QC (Recipe Verification),
https://textiletrainer.com/sizing-ingredients-with-their-function/
JEMIT PDF: Sizing Efficiency QC (Defects Reduction),
https://jemit.aspur.rs/archive/v3/n1/3.pdf
Sage Journals: Warp Sizing Review (Process Checkpoints),
https://journals.sagepub.com/doi/abs/10.1177/00405175241235400
TextileLearner: Sizing Defects Causes (Flaking/Sticking),
https://textilelearner.net/sizing-defects-causes-and-remedies/
TextileLearner: Yarn Sizing Preparatory QC,
https://textilelearner.net/yarn-sizing-important-warp-preparatory-process/
GlobalPolyester: Sizing Problems QC Guide (Tension/Penetration),
https://globalpolyester.com/common-problems-in-textile-sizing-a-simple-guide/
TextileSchool: Sizing Operations (Drying/Beam QC),
https://www.textileschool.com/1080/sizing-operation-for-textiles/
Wikipedia: Sizing Machine QC (Historical Standards),
https://en.wikipedia.org/wiki/Textile_sizing_machine
Fibre2Fashion: Size QC in Fabrics (Post-Sizing Tests),
https://www.fibre2fashion.com/industry-article/3703/identification-of-type-of-size-in-woven-fabrics
NPTEL Archive: Sizing Bath Preparation (Viscosity Control),
https://archive.nptel.ac.in/content/storage2/courses/116102016/m-10/desizing.htm
TextileChemistry Blog: Desizing Material QC (Starch Residue),
https://drmsparmar.blogspot.com/2014/12/how-to-test-desized-material-starch.html
PMC: Starch Sizing QC Parameters,
https://pmc.ncbi.nlm.nih.gov/articles/PMC6572457/
PMC: Warp Moisture/Strength Testing,
https://pmc.ncbi.nlm.nih.gov/articles/PMC10820382/
ACS ES&T: Sizing Film Defects Analysis,
https://pubs.acs.org/doi/10.1021/es504988w
Sekisui SC: PVOH Sizing QC (Film Uniformity),
https://www.sekisui-sc.com/blog/7-reasons-to-use-polyvinyl-alcohol-for-textile-warp-sizing/
SiamModifiedStarch: Warp Sizing QC Metrics,
https://www.siammodifiedstarch.com/product/non-food/detail/Warp-Sizing
ZDHC Guidelines (Sizing Effluent QC),
https://downloads.roadmaptozero.com/output/ZDHC-Wastewater-Guidelines
GOTS Manual (Sustainable Sizing Checkpoints),
https://global-standard.org/images/Implementation_Manual_7.0_Second_Revision_Draft.pdf
Persistence: Sizing Market QC Trends,
https://www.persistencemarketresearch.com/market-research/textile-sizing-chemicals-market.asp
Slideshare: Sizing QC Presentations (Viscosity/Drying),
https://www.slideshare.net/slideshow/desizing-34238292/34238292
Liked it? Share it with your people.
Disclaimer
The information provided in this blog is intended solely for educational and informational purposes within the textile industry. While the content references technical concepts, sizing and desizing practices, and general chemical information, it does not constitute professional, commercial, or operational advice for any specific textile process or production environment.
Process conditions, chemical selections, and operational parameters may vary significantly across mills, machinery types, fabric constructions, and environmental constraints. Readers should always consult qualified technical professionals, internal laboratory data, and product-specific Technical Data Sheets before making any decisions related to textile processing.
Any references to Alpenol, Sizaltex, or other products are included only for contextual, educational, and illustrative purposes and should not be interpreted as endorsements, recommendations, or guarantees of performance. The authors assume no responsibility for decisions made based on the information contained herein.