A Quality Issue Inside the Steam Tunnel
A beverage customer using PET-G shrink sleeves reported a quality issue during steam shrink application at their production plant. During shrinking through steam tunnel:
- Water droplets formed inside the sleeve
- Sleeve appearance became hazy
- Graphics visibility reduced
- Moisture marks remained after shrinking
The issue was mainly observed on refrigerated beverage bottles and high-speed production lines.
What the Customer Saw on the Line
During steam shrinking:
Fine water droplets appeared between bottle and sleeve
Sleeve surface looked foggy
Water marks became visible after cooling
Premium glossy appearance reduced
Conditions That Increased the Issue
The issue increased during:
High humidity conditions
Excess steam pressure
Low tunnel ventilation
Key Observations
Excess Steam Condensation
Steam inside tunnel condensed rapidly on cold bottle surface.
Trapped Moisture Between Sleeve & Bottle
Condensed water could not escape during shrinking.
No Anti-Moisture Treatment on Sleeve Backside
Inner sleeve surface allowed droplet accumulation.
Uneven Steam Distribution
Direct steam impact created localized condensation zones.
Primary Root Cause
Combination of:
- Cold bottle temperature
- High steam exposure
- Lack of backside anti-moisture coating
- Inadequate steam tunnel exhaust
This caused steam condensation to remain trapped between sleeve and container.
Three Corrective Actions
Backside Anti-Moisture Coating Introduced
A special anti-fog coating was applied on inner sleeve surface.
Water spread as thin transparent film instead of droplets.
Steam Tunnel Optimization
Changes Made:
- Improved tunnel exhaust airflow
Reduced condensation formation.
Sleeve Fit Optimization
Shrink profile modified to reduce air pocket formation.
Better sleeve-to-bottle contact achieved
Validated on the Production Line
Steam Shrink Trial
Before Improvement:
- Visible droplets trapped inside sleeve.
After Improvement:
- Clear sleeve appearance achieved
Visual Inspection
Gloss and print clarity maintained.
Customer Production Trial
Stable performance at full production speed.
From Severe to Solved
What This Job Taught Us
- 01Steam condensation is highly affected by bottle temperature difference.
- 02Backside anti-moisture coating is essential for steam shrink applications.
- 03Steam tunnel balancing is critical to avoid localized water formation.
- 04Proper exhaust ventilation reduces trapped moisture.
- 05Air pockets between bottle and sleeve increase condensation visibility.
- 06PET-G sleeves require optimized steam exposure for premium appearance.
Problem Resolved
The water droplet issue during steam shrink application was caused by condensation trapped between the PET bottle and PET-G shrink sleeve. Through backside anti-moisture coating, steam tunnel optimization, and bottle temperature stabilization, the problem was successfully resolved.
The corrective actions improved:
- Sleeve transparency
- Shelf appearance
- Production efficiency
- Customer satisfaction
The Work, Up Close
