Temperature and Humidity Control in Printing Workshops: Tuning Techniques for Offset Printing Ink Drying Rate and Lamination Film Compatibility During Plum Rain Seasons

Every year, affected by monsoons and marine climates, regions across the globe including Southeast Asia, East Asia, Western Europe, and Eastern North America experience prolonged rainy and high-humidity seasons. Persistent wet weather often pushes the relative humidity of production workshops above 85% RH alongside fluctuating temperatures, creating widespread challenges for printing and post-press processing. Industry research data indicates that during extended high-humidity periods, the yield rate of the lamination process for printing enterprises worldwide drops by an average of 10%–15%. Over 70% of quality defects stem from slow-drying offset printing ink, blistering, delamination, and surface offsetting of lamination film. These issues not only drive up consumption costs of raw materials such as ink, film substrates, and base paper but also frequently result in product rework and delayed order delivery. Combining fundamental printing process principles with frontline workshop operational experience from domestic and overseas manufacturers, this paper compiles a systematic temperature and humidity control scheme, optimized strategies to accelerate offset printing ink drying, and supporting tuning techniques for lamination film, helping printing companies worldwide mitigate the impacts of persistent rainy, high-humidity weather, stabilize product pass rates, and improve overall production scheduling efficiency.

1. Fundamental Impacts of Temperature and Humidity on Offset Printing Ink Drying

Curing of offset printing ink relies on two simultaneous reactions: solvent volatilization and oxidative polymerization. High humidity and low temperature directly suppress drying efficiency. Water vapor in the air forms a thin continuous water film on the surface of freshly printed ink layers, obstructing solvent volatilization and slowing ink drying by over 30%. A standard drying cycle of 2–4 hours can be extended to more than 8 hours. If workshop temperatures remain below 20°C for long periods, crosslinking and curing of ink resins decelerate further, easily causing pseudo-drying where the surface appears dry while the inner ink layer remains uncured. Common production defects such as offsetting of stacked printed sheets, ink transfer after lamination, surface specks, and faint color deviation mostly originate from incomplete ink drying.
2. Compatibility Conflicts Between Temperature, Humidity and Lamination Film

Lamination performance is extremely sensitive to ambient temperature and humidity, and damp conditions during plum rain seasons severely undermine lamination compatibility. Conventional BOPP lamination film has strong moisture absorption capacity; elevated surface moisture content of film substrates under high humidity weakens the adhesion of adhesive layers, readily leading to blisters, hazy whitening, and insufficient bonding after lamination, with product peel strength reduced by 20%–30%. Meanwhile, frequent fluctuations in temperature and humidity create mismatched thermal expansion and contraction coefficients between paper and film, triggering edge curling, uneven tension, and partial wrinkling of laminated products.

Statistics from frontline production show that in workshops without temperature and humidity control during plum rain seasons, blistering accounts for 45% of all lamination defects and delamination accounts for 28%, making these the primary bottlenecks limiting product yield.

1. Benchmark Ambient Parameters for Workshops

Aligning with the dual process requirements of offset printing and lamination, the optimal production environment standard for workshops during plum rain seasons is a temperature range of 20–25°C and relative humidity of 50%–65% RH. Fine-tuning can be implemented based on printing substrates:

For dense, smooth stocks such as coated art paper and matte coated paper, maintain humidity at 50%–55% RH to prevent moisture absorption and paper deformation.

For porous, absorbent substrates including cardboard and kraft paper, adjust humidity to 55%–65% RH to avoid excessive paper dryness and static electricity buildup.

Uniform environmental conditions must be maintained across the entire workshop, with temperature differences between any two zones not exceeding 3°C and relative humidity differences not exceeding 10% RH, eliminating process instability triggered by localized environmental fluctuations.
2. Practical Operation Tips for Environmental Regulation Equipment

Precision operation of dehumidifiers: Deploy industrial dehumidifiers with a daily dehumidification capacity of 15–20 L per 100 m² of workshop floor area. Run all units at medium-to-high fan speeds during humidity peaks such as rainy days and early mornings, with targeted dehumidification directed at offset presses and laminators. Empty dehumidifier water tanks daily to avoid condensed water re-evaporation that negates dehumidification effects.

Standardized commissioning of air conditioning systems: Activate cooling and dehumidification mode uniformly with a baseline temperature set at 23°C. Prevent air outlets from blowing directly onto production equipment by installing wind deflectors and adjusting airflow directions to eliminate localized temperature disparities, which cause uneven ink drying and paper expansion/contraction deformation.

Comprehensive auxiliary moisture prevention: Keep workshop doors and windows closed during production hours. Place silica gel desiccants or quicklime at the base of equipment and floor corners for moisture absorption, with 1–2 kg of desiccant deployed per 10 m² and replaced on a regular basis. Store raw materials including offset printing ink and lamination film on sealed racks in warehouses to block moisture absorption and deterioration at the source.
3. Process Optimization for Accelerated Offset Printing Ink Drying

Ink formulation adjustment: Prioritize fast-oxidizing, stable-curing vegetable oil-based fast-drying offset printing ink, which delivers a drying efficiency 25% higher than standard ink. Add dedicated driers as required: cobalt drier at 0.3%–0.5% of total ink weight and manganese drier at 0.1%–0.2%. Strictly control dosages to avoid brittle ink layers and yellow discoloration.

Adapted printing parameters: Reduce ink film thickness moderately to 3–5 μm, a 10%–15% reduction from standard operating conditions to lower drying loads. Simultaneously raise the infrared drying temperature of offset presses to 60–70°C with medium fan speeds. Workshops equipped with auxiliary UV drying devices may operate them at low power to balance drying performance and paper stability.

Post-printing drying treatment: Extend sheet resting time for finished printed products, doubling or tripling the standard duration used in dry seasons. For rush orders, place sheets in constant-temperature drying equipment at 45–50°C for 30–60 minutes to ensure complete ink curing and eliminate pseudo-drying risks.

1. Lamination Film Selection and Pre-Treatment

Scientific substrate selection: Prefer modified low-moisture-absorption BOPP lamination film, whose water absorption rate is 40% lower than conventional film, delivering stronger adhesive layer adhesion and superior moisture resistance. Strictly control film shelf life; avoid stock film stored for more than six months. Use up all opened film within 24 hours and seal residual material tightly for storage.

Constant-temperature conditioning pre-treatment: All lamination film must be stored in the production workshop under constant temperature and humidity for 24 hours prior to machine loading to eliminate internal stress and moisture disparities within the film. Equip laminators with static elimination devices to treat film surfaces before lamination, preventing dust adsorption caused by static electricity that creates bonding defects.
2. Precision Calibration of Laminator Operating Parameters

Temperature regulation: Fine-tune lamination temperature based on ink curing status, raising settings by 3–5°C compared to standard conditions within an overall range of 80–100°C. Use low-temperature lamination at 80–85°C for fully dried printed sheets; increase temperature to 90–100°C for semi-finished products with partially dried ink, preventing ink softening, transfer, and plate smearing from excessive heat.

Pressure adjustment: Moderately increase roller lamination pressure to 0.3–0.5 MPa, a 0.1 MPa uplift from standard settings to strengthen tight bonding between film and ink-paper substrates. Calibrate roller parallelism with a tolerance of ≤0.02 mm to avoid wrinkling caused by uneven localized pressure.

Line speed matching: Reduce laminator operating speed from the standard 30–40 m/min to 20–25 m/min, extending hot-press bonding duration by 3–5 seconds to enable full melting and penetration of lamination film adhesive layers, matching the slow curing characteristics of offset printing ink during plum rain seasons.
3. Emergency Remedies for Common Defects

Blistering: Lamination blisters mostly stem from excessive ambient humidity or incomplete ink drying. Immediately shut down equipment and activate dehumidifiers to lower workshop humidity below 65% RH. Subject unlaminated semi-finished sheets to secondary drying for 30 minutes before processing. Slightly blistered finished products can be repaired via secondary hot pressing at 85°C and 0.4 MPa.

Surface offsetting: Test ink dryness by wiping sheets with paper towels; extend resting time for incompletely dried products. Switch to high-adhesion lamination film or add 0.5%–1% anti-offset agent to offset printing ink to enhance scratch resistance and anti-offset performance of ink layers.

Delamination: First inspect film quality and replace expired substrates with yellowed or brittle adhesive layers immediately. Simultaneously raise lamination temperature to 95°C and pressure to 0.5 MPa to optimize bonding performance and resolve delamination issues.

Quality control for printing operations during plum rain seasons is a systematic undertaking centered on dynamic coordination of three core elements: environment, raw materials, and processes. Stable workshop temperature and humidity form the production foundation; scientific ink drying processes and calibrated lamination parameters are critical to quality assurance; and moisture-resistant functional raw material selection eliminates defects at the source. Synergistic control of all three factors efficiently resolves production challenges introduced by damp weather.

Enterprises should establish long-term management mechanisms: deploy a real-time temperature and humidity monitoring system with regular data logging and timely equipment adjustment; formulate special operating specifications and defect emergency response plans for plum rain seasons, paired with enhanced hands-on training for staff; regularly calibrate and maintain core equipment including dehumidifiers, laminators, and offset presses to sustain stable production.

From an industry development perspective, moisture-resistant specialized offset printing ink and solvent-free bio-based lamination film and other green functional materials will become vital solutions for printing enterprises to adapt to extreme weather, boost quality while cutting costs, and advance sustainable green manufacturing. Printing companies may proactively adopt new materials and processes, optimize production systems and procurement standards, and further strengthen production stability and core market competitiveness.