What Causes Bubbles in Laminated Glass in 2026? A Comprehensive Analysis of the Causes and Solutions for Bubbles in Laminated Glass
In the high-end architectural and decorative glass processing industry, almost no defect is more frustrating than "bubbling." When you remove carefully prepared glass from the laminating furnace or autoclave and find it riddled with bubbles, it means high rework costs, a sharp drop in yield, and delivery delays.
Bubbles not only severely damage the optical effects and aesthetics of the glass, leading to customer rejection; in more serious cases, they are also a signal of internal stress concentration and microstructural failure, easily evolving into large-scale delamination, posing a fatal structural safety risk.
With increasingly stringent global building safety regulations in 2026, identifying the root causes of this defect is particularly urgent. This article will directly address the core question: What causes bubbles in laminated glass and how can manufacturers prevent them? We will provide a comprehensive analysis of the causes and ultimate solutions to Bubbles Problems in Glass Lamination, from materials science and processing technology to environmental control.
What is Laminated Glass and its Laminated Structure?
EVA Interlayer for Laminated Glass
To solve the bubbling problem, it's essential to first understand the basic physical structure of laminated glass.
Basic Composition of Laminated Glass
Laminated glass is essentially a "sandwich" structure. It consists of two or more layers of glass sheets with one or more polymer films (interlayers) sandwiched in between. Through a high-temperature, high-pressure (or vacuum heating) lamination process, the glass and interlayer are permanently bonded together, creating a composite safety glass.
Common Interlayer Types
The material of the interlayer directly determines the performance and processing requirements of the laminated glass:
EVA (Ethylene-vinyl acetate): A thermosetting material with good flowability, commonly used in decorative glass, smart glass, and outdoor high-humidity environments.
PVB (Polyvinyl butyral): A thermoplastic material with the widest application, primarily used in automobiles and conventional buildings, but extremely sensitive to humidity.
SGP (Ionomerized Plated Glass): Ultra-high strength and stiffness, designed specifically for structural glass and hurricane-resistant glass.
Functional films: Such as PDLC smart dimming films used to switch between transparent and frosted states.
Main Manifestations of Bubbles in Glass Lamination
In actual production, bubbles are not uniform. Experienced engineers can often directly deduce the problem by observing the morphology of the bubbles.
Microbubbles: These appear as dense clusters of pinhead-sized bubbles. They are usually scattered around the edges of the glass or around tiny impurities on the glass surface. This is mostly related to poor venting or localized contamination.
Air pockets: These appear as large, irregularly shaped bubbles, usually appearing in the central area of the glass. These bubbles are extremely visible and severely affect optical performance. They are usually caused by premature temperature rise during lamination, leading to edge sealing and preventing the central air from escaping.
Delamination bubbles: These bubbles are more insidious. They are often invisible when the glass is first produced in the factory, but gradually appear after several months or even years of use, often accompanied by whitening at the edges. This is usually directly related to the material stability and weather resistance of the interlayer.
What Causes Bubbles in Laminated Glass? – Analysis of 5 Core Causes
What exactly causes this annoying bubbling phenomenon? After extensive laboratory data and on-site factory investigations, we have summarized the following five core causes:
Incomplete Cleaning of Glass Surface
The cleanliness of the glass surface is fundamental to lamination. If the cleaning machine fails to thoroughly remove cutting oil, dust particles, or residual moisture from the glass surface, these impurities will form a tiny insulating layer between the glass and the interlayer. During high-temperature lamination, the residual air or moisture expands and cannot escape smoothly, directly leading to the formation of microbubbles.
Excessive Moisture Content in the Interlayer
This is the "number one killer" for bubbling in PVB and low-end EVA. If the ambient humidity is not properly controlled during storage or lamination, the polymer film will absorb moisture from the air. When the lamination temperature rises above 100°C, the moisture hidden inside instantly vaporizes into water vapor. The water vapor trapped inside the glass has nowhere to escape and, upon cooling, turns into bubbles.
Inadequate Vacuum Degassing Process
In processes using vacuum laminators, the degassing stage is crucial. Common errors include: aging vacuum bags (or silicone rings) leading to poor sealing; insufficient pre-vacuuming time to completely remove internal air; or excessively rapid heating. When the internal air is not completely removed, the edge film melts and seals the edges, trapping air inside the glass. This phenomenon is particularly common in small and medium-sized production lines.
Improper Lamination Temperature and Pressure Control
Temperature and pressure are a double-edged sword in the lamination process:
Too low a temperature: The film fails to reach a fully molten state, unable to fill microscopic imperfections on the glass surface, leaving gaps.
Too high a temperature: Some low-quality materials undergo thermal decomposition under excessively high temperatures, producing volatile gases (outgassing) and forming numerous bubbles.
Unstable pressure: In autoclave processes, if the holding time is insufficient or the pressure is released too early during the cooling stage, the tiny gases originally compressed within the resin will re-expand into visible bubbles.
Immature Interlayer Technology
Don't place all the blame on factory operators; the inherent characteristics of the material itself are equally problematic. Low-end materials have unstable cross-linking systems, extremely poor flow control, or contain large amounts of residual volatile organic compounds (VOCs) from production. Using mature, high-end interlayer technology for laminated glass, with its stable molecular structure and optimized rheological properties, can significantly reduce the bubble rate from both physical and chemical perspectives.
The Impact of Different Interlayers on Bubble Formation
Different interlayer materials have different risks and mechanisms for causing bubbling. The following English table clearly shows the relationship between material properties and bubbling rate:
Table 1: Influence of Interlayer Types on Bubble Formation
|
Interlayer Type |
Bubble Risk Level |
Material Stability & Characteristics |
|
Low-end EVA Interlayer |
High |
Highly prone to yellowing, outgassing, and thermal decomposition if over-heated. |
|
High-quality EVA Interlayer |
Low |
Excellent rheology (flowability) fills gaps perfectly; thermoset cross-linking ensures long-term stability. |
|
PVB (Standard) Interlayer |
Medium |
Extremely sensitive to ambient humidity; requires strict climate-controlled clean rooms to prevent moisture bubbles. |
|
SGP (Ionoplast) Interlayer |
Very Low |
Highly stable molecular structure, low moisture absorption, requires precise autoclave processing for optimal clarity. |
How to Systematically Solve Bubbles Problems in Glass Lamination？
Solve Bubbles Problems in Glass Lamination
Solving bubble problems cannot rely on symptomatic treatment; a systematic prevention and control mechanism must be established.
Strict Laminated Glass Production Environment Control
Minimize uncontrollable environmental factors.
Cleanroom: The lamination room must meet Class 10,000 or Class 100,000 cleanroom standards.
Temperature and Humidity Control: For PVB, the relative humidity of the workshop must be strictly controlled at around 25%; even when using EVA, humidity is recommended to be controlled within 30–40%.
Glass Pre-treatment: Cleaned glass must undergo thorough high-temperature pre-drying to ensure absolutely zero moisture residue on the surface.
Optimize Lamination Process Parameters
Establish standardized operating procedures (SOPs) for your specific equipment (vacuum furnace or autoclave).
Sufficient Pre-compression Time: Before heating, allow the vacuum system sufficient time (usually 15-30 minutes of cold evacuation) to purge all air.
Stepped Heating Curve: Avoid rapid heating. Set reasonable insulation intervals to allow sufficient time for air to escape before the edges seal.
Maintain Sufficient Vacuum: Ensure the vacuum pump is performing well; the vacuum level must not fall below -0.090 MPa throughout the entire heating and cooling cycle.
Choose High-Quality Interlayer
This is a shortcut to improving yield. Choose branded materials with low volatility, stable cross-linking technology, high transparency, and good flowability. Excellent interlayers have a wider processing temperature window, maximizing the tolerance for minor process deviations.
Reasons for Bubbles After Long-Term Use (Delayed Bubbling)
Some glass is flawless when it leaves the factory, but bubbles appear after a year of outdoor installation. This "delayed bubbling" is usually attributed to the following reasons:
- UV Aging: Inferior materials undergo polymer chain breakage and degradation under long-term UV exposure, producing gases.
- High Humidity Environment Corrosion: Especially with PVB, if the edges are not properly sealed, moisture will slowly penetrate into the film, leading to edge bubbling and delamination.
- Insufficient Cross-linking: If the insulation time during EVA lamination is insufficient, the cross-linking reaction is incomplete, significantly reducing the material's anti-aging properties and making it prone to physical property degradation and bubbling later.
How to Determine if Bubbles are a Material or Process Issue?
When faced with a batch of defective bubbly products, shirking responsibility is pointless. We need scientific diagnostic methods:
Timing Analysis
Immediate Occurrence (Appearing immediately after firing): Primarily a process issue (e.g., glass contamination, vacuum leakage, incorrect temperature settings).
Occurrence after 1–3 years of use: Primarily a material weather resistance issue (e.g., weak UV resistance, cross-linking system collapse).
Scientific Diagnostic Testing
Use industry standard tests to determine liability:
Table 2: Diagnostic Testing Methods for Lamination Defects
|
Test Method |
Primary Purpose |
Targeted Defect / Quality Check |
|
Gel Content Test (Cross-linking Degree Test) |
Measures the curing degree of EVA film. |
Identifies if post-installation bubbles are due to under-curing during lamination. |
|
Boil Test (Water Resistance) |
Simulates extreme humidity and heat. |
Checks edge sealing quality and the interlayer's resistance to moisture-induced delamination. |
|
UV Aging Test (QUV) |
Simulates years of solar exposure. |
Determines if the interlayer material is prone to chemical breakdown and delayed outgassing. |
Future Trends: How to Reduce Bubbling Rate Through Technological Upgrades?
Looking towards 2026, the glass deep processing industry is transforming towards intelligent and refined processes. Future anti-bubbling strategies will rely on more advanced interlayer technology for laminated glass:
More Stable Cross-linking System: New thermosetting resins can achieve uniform cross-linking over a wider temperature range, reducing localized incomplete curing caused by temperature differences.
Low VOC Environmentally Friendly Formula: Eliminating volatile substances at the source completely prevents spontaneous bubbling at high temperatures.
Intelligent Temperature Control Lamination Equipment: The next-generation lamination furnace will be equipped with multi-point temperature sensors and adaptive pressure algorithms to compensate for heat differences in real time, ensuring absolutely uniform heating of every inch of glass.
FAQ
Q1: What causes bubbles in laminated glass?
The main causes include: residual oil or moisture on the glass surface due to incomplete cleaning; excessive moisture content due to improper storage of the interlayer; insufficient vacuum degassing during lamination; and unreasonable setting of heating temperature and pressure curves.
Q2: Are bubbles in laminated glass dangerous?
This depends on the size and location of the bubbles. Minor, tiny bubbles mainly affect optical aesthetics; however, large areas of bubbles or continuous edge bubbles indicate lamination failure, which can easily develop into severe delamination, significantly reducing the glass's explosion-proof and structural safety performance.
Q3: How do you prevent bubbles in laminated glass?
Prevention hinges on three key controls: strictly controlling workshop temperature and humidity and glass cleanliness; precisely optimizing vacuuming time and stepped heating parameters; and rejecting inferior materials, selecting high-quality interlayers with stable performance.
Q4: Is interlayer quality related to bubble formation?
Absolutely. Advanced interlayer technology for laminated glass possesses excellent rheological properties and low volatility, not only perfectly filling tiny gaps but also maintaining extremely high physical stability at high temperatures, fundamentally reducing the probability of bubbling.
Conclusion
In summary, bubbles in laminated glass are never an isolated phenomenon caused by a single reason; they are the result of the combined effects of material quality, processing techniques, and the workshop environment.
To remain competitive in a fiercely competitive market, the key to improving production stability lies in: continuously optimizing and validating lamination process curves, strictly controlling the temperature and humidity of the production environment, and resolutely adopting mature and reliable interlayer technology for laminated glass.
For manufacturers committed to improving yield, pursuing long-term stable performance, and maintaining brand reputation, understanding the mechanisms of bubble formation and selecting a technologically superior interlayer supplier is the most crucial step towards success. Contact E&N for the highest quality interlayers and professional advice on laminated glass processing.