Both shoe manufacturers and consumers may have encountered the following situations:
- Newly produced shoes, unsold and unworn, suddenly develop stains of other colors on the uppers or soles.
- The border between white uppers and dark soles gradually shows signs of color bleeding.
These phenomena are related to color migration. What exactly is color migration? How does it occur? How can it be tested and prevented? Let PFI’s experts provide a detailed explanation.
1. What Is Color Migration in Shoes?
Color migration in shoes refers to the phenomenon where dye or pigment molecules transfer from one material to another during production, transportation, storage, or use. This commonly occurs between upper materials (such as leather or synthetic fibers) and soles.
2. Causes of Color Migration
1) Dyeing Process
- If low-quality dyes are used, they may not adhere firmly to the shoe material, increasing the risk of color migration.
- Improper dyeing techniques—such as insufficient dyeing time or incorrect temperature control—can weaken the bond between the dye and material, leading to migration.
2) Material Compatibility
Certain materials (e.g., leather and rubber) may have compatibility issues, allowing dyes or pigments to migrate from one material to another.
3) Chemical Additives
Additives used during dyeing (e.g., softeners, waterproofing agents) may react with dyes, dissolving them and creating free pigments. These pigments are more prone to migration under high temperature or humidity.
4) Fixation Process
Fixation is a critical step in preventing color fading and migration. Inadequate fixation or improper treatment can prevent dyes from forming a stable bond with the material, resulting in color transfer.
3. Testing Methods for Color Migration
1) Adhesion Method
Two different single-layer or composite materials from the shoe are pressed together between glass plates under a pressure of (5.2 ± 0.5) kPa. The sample is stored in darkness at (60 ± 2)°C for a specified duration, then compared to an untreated control sample to assess color migration.
Applicable Standards:
- ISO 17701:2016 Footwear — Test methods for uppers, lining and insocks — Colour migration
- GB/T 3903.42-2019 Footwear — Test methods for uppers, lining and insocks — Color migration
2) Aging Method
The entire shoe is placed in a high-temperature or high-humidity environment for a set period, then compared to an untreated shoe to check for color migration.
Applicable Standards:
- ISO 20870:2017 Footwear — Ageing conditioning
- GB/T 3903.7-2019 Footwear — Whole shoe test methods — Aging treatment
4. How to Prevent Color Migration?
1) Material & Dye Selection
- Use high-color-fastness dyes to ensure strong adhesion to materials.
- Opt for migration-resistant pigments (e.g., certain polymer-based pigments) to minimize color transfer.
2) Optimize Dyeing Processes
- Strictly control the dosage of additives and process parameters to reduce dye leaching.
- Apply fixing agents after dyeing to enhance dye-fiber bonding:
- For leather uppers: Use chrome tanning or retanning.
- For synthetic leather: Employ high-temperature setting or UV curing to stabilize dyes.
- Rinse materials post-dyeing to remove excess/unbound dyes.
- Monitor pH levels, as some dyes degrade in acidic/alkaline conditions, increasing migration risk.
3) Post-Treatment Optimization
- Apply anti-migration agents (e.g., silicone oils, fluorochemical waterproofing agents) to form a protective film and reduce dye leaching.
- High-temperature setting: Heat treatment can stabilize dyes in synthetic materials.
- UV curing: Enhances migration resistance in synthetic leather coatings.
- Add a barrier layer: Insert a隔离层 between uppers and soles to block dye/pigment transfer.
Color migration in shoes is a complex quality issue that affects both aesthetics and user experience. If you have further questions, contact PFI’s expert team for tailored solutions.