Strictly Control Workshop Temperature & Humidity To Resolve Whitening And Hazing Issues Of Lamination Film in Plum Rain Season

When summer arrives, regions across China enter the hot and humid plum rain season featuring persistent rainy weather, saturated ambient humidity and drastic diurnal temperature swings, which severely impede the post-printing lamination process in the packaging and printing sector. Serving as a critical process to upgrade packaging appearance and protect finished printed products, lamination with lamination film is extremely sensitive to production temperature, humidity, raw material conditions and technical parameters. Affected by the peculiar climatic conditions of the plum rain season, manufacturers across the industry commonly encounter quality defects including laminated film whitening, surface hazing, poor transparency and overall grey discoloration. Such flaws lead to product rework, scrappage, customer complaints and delayed order fulfillment, pushing up material and labor costs considerably and damaging corporate production efficiency and brand reputation. To tackle this seasonal production challenge, numerous packaging and printing enterprises carry out targeted refined improvements from four dimensions: production environment, raw materials, processing technology and quality inspection. By comprehensively optimizing lamination workflows for rainy seasons, these businesses successfully eliminate recurrent whitening and hazing defects, achieving the goals of quality improvement, cost reduction and stable output in summer production.

The plum rain season is defined by high humidity, scarce sunlight and poor ventilation, with relative humidity inside workshops consistently exceeding 70% and nearing saturation on heavily rainy days, which falls far short of the standard process requirements for lamination with lamination film. Industrial statistics reveal that the reject rate of laminated finished products surges 3 to 5 times in June and July each year compared with dry seasons, with whitening and hazing accounting for over 80% of all defective products, ranking as the most prominent quality issue for post-printing production in summer.

Most printing factories follow conventional production routines without customized operational protocols for the plum rain season. Lacking systematic temperature and dehumidification equipment, their workshops allow continuous inflow and accumulation of moist outdoor air. Tiny water vapor suspended in the air adheres to paper surfaces, lamination film substrates and hot-melt adhesive layers during production; once enclosed between film and paper after lamination, trapped moisture cannot evaporate and eventually results in foggy, dull and low-transparency surface imperfections.

Such defects frequently emerge on high-end color cartons, gift packages, food and pharmaceutical packaging, hardcover books and other premium printed goods. Minor flaws downgrade product grades, while severe defects fail acceptance criteria and trigger full-batch rework or scrappage. This wastes paper stock, lamination film, printing ink and other raw materials, raises extra expenses for reworking labor and equipment maintenance, delays delivery of high-end and foreign trade orders, and may even incur customer complaints or terminated cooperation. Consequently, it has become a major bottleneck restricting stable high-quality production and on-time delivery for manufacturers throughout the plum rain period.

To eradicate lamination whitening and hazing fundamentally, corporate technical teams conduct on-site inspections combining processing principles, environmental data and raw material conditions, pinpointing four root causes to facilitate targeted rectification.

First, excessive ambient humidity in production workshops. Outdoor humidity remains persistently high in plum rain season; indiscriminate window ventilation in many plants draws massive damp vapor into production zones. As porous and hydrophilic materials, paper easily absorbs moisture leading to excessive moisture content and slight surface expansion. Trapped moisture between laminated layers cannot escape and directly causes whitening and fogging defects.

Second, mismatched temperature and humidity ratios. Lamination imposes strict stability requirements on temperature and humidity, which directly determine hot-melt adhesive curing performance and film bonding quality. Dramatic diurnal temperature fluctuations and inconsistent indoor climate control during plum rains result in uneven curing speed of hot-melt adhesives and unstable lamination adhesion. Gaps formed between film and paper trap water vapor and trigger widespread surface hazing.

Third, inadequate moisture-proof management of raw materials. Many manufacturers have poorly equipped warehouses without dedicated moisture-proof storage areas. Improper sealing of lamination film and printing paper leaves raw materials exposed to humid air prone to moisture absorption and deterioration. Moisture-laden lamination film suffers reduced substrate toughness and failed hot-melt adhesive performance, while over-humid paper directly generates bulk lamination defects once fed into production. In addition, raw materials left uncovered after unpacking and unwinding absorb secondary moisture and exacerbate quality risks.

Fourth, outdated fixed technical parameters unsuitable for humid conditions. Most factories retain process settings designed for dry weather without adjustments for high-humidity plum rain environments. Elevated ambient humidity renders original lamination temperature, paper feeding speed and laminating pressure inappropriate. Insufficient preheating and overly fast paper feed lead to incomplete hot-melt adhesive melting and inadequate air evacuation, whereas uneven rolling pressure creates localized bonding voids where trapped moisture induces film whitening and hazing.

Based on identified root problems, manufacturers abandon extensive production modes and adopt refined full-process management with targeted corrective actions to resolve seasonal lamination quality issues systematically.

1. Deploy specialized equipment to realize precise temperature and humidity regulation

Enterprises upgrade workshop facilities by installing industrial dehumidifiers, constant temperature & humidity integrated machines and intelligent environmental monitoring terminals across production areas to monitor real-time climatic data round the clock. Indoor temperature is maintained between 18°C and 25°C, with relative humidity kept within the optimal 45%–65% range for lamination production. Ventilation rules are standardized: air exchange is prohibited during damp early mornings and rainy spells and only permitted under dry weather; workshops stay sealed for continuous dehumidification at other times to block vapor intrusion at source and sustain dry stable production surroundings.

2. Optimize warehouse management to prevent damp raw materials from entering production

Factories renovate storage spaces into exclusive moisture-proof warehouses fitted with damp-proof base plates, thermal insulation and dedicated warehouse dehumidification equipment to preserve constant dry storage conditions. An incoming material inspection system is enforced to test moisture content of paper and lamination film; any damp stock is rejected for warehousing and processing. On-site material usage is regulated to unpack and consume raw materials on demand, with leftover supplies promptly hermetically sealed to avoid secondary moisture uptake and eliminate hidden quality hazards originating from base materials.

3. Revise process parameters to adapt to high-humidity production conditions

Technical teams formulate customized rainy-season operation specifications tailored for humid environments. Properly raised preheating temperature ensures thorough and uniform melting of hot-melt adhesives; slower paper feeding extends air exhaust time during lamination for tight seamless bonding between film and paper and complete vapor discharge. Calibrated rolling pressure delivers uniform compaction across contact surfaces to eliminate partial bonding gaps, effectively eliminating whitening and hazing caused by mismatched processing and improving lamination transparency and flatness.

4. Implement full-process refined management and routine inspection protocols

A comprehensive inspection mechanism covering pre-shift, mid-shift and post-shift operations is established. Constant temperature and dehumidification equipment is switched on in advance before startup; production can only commence after environment, machinery and raw material status pass pre-production checks. The first-article inspection rule is strictly executed: the first piece of every production batch undergoes comprehensive checks on appearance, transparency and adhesion before mass production kicks off. More frequent spot checks are arranged throughout production, with timely parameter fine-tuning responding to minor ambient changes to spot and fix defects early and avoid bulk defective output.

Full-scale optimization across environment control, raw material management, processing technology and quality inspection completely eliminates seasonal recurring defects including whitening, hazing and grey discoloration in lamination. Finished laminated products feature bright transparent surfaces and uniform flat bonding that fully satisfy strict acceptance standards of high-end packaging and export orders with drastically upgraded qualification rate.

Production statistics indicate that targeted reforms slash the plum rain season's lamination reject rate by over 90%, greatly cutting rework and scrapped products, boosting raw material utilization and lowering overall expenditure on materials and labor. Stable product quality eliminates delayed shipments and customer complaints stemming from lamination defects, accelerating order delivery efficiency and lifting manufacturers' summer production stability and market competitiveness. The refined rainy-season lamination control protocol formed after rectification boasts strong operability and wide applicability, offering replicable practical experience for the whole industry to cope with seasonal production difficulties.

Lamination quality defects during plum rain represent a common seasonal challenge across the packaging and printing industry, primarily stemming from sloppy environmental control, poorly adapted processing techniques and nonstandard raw material administration. Targeted rectifications effectively remove production bottlenecks and resolve persistent industrial pain points. Moving forward, packaging and printing manufacturers will consistently advance refined production management by institutionalizing and normalizing rainy-season exclusive lamination standards. Enterprises will dynamically optimize temperature-humidity control, warehouse storage and technical parameters to flexibly adjust production schemes in response to seasonal climate shifts, improving adaptability between processing conditions and production environments. Standardized and refined management helps evade seasonal operational risks, consolidate product quality foundations and facilitate high-efficiency, stable and high-quality development of the packaging printing industry.