Anti-mold treatment for wet plate pallets: Parameter differences between immersion and spray in no-dry scenarios

Common pallet materials such as pine, poplar, mixed wood, Chinese pine, and masson pine typically proceed directly from sawing or processing to the next stage without drying yards or kilns. This means mold prevention cannot be limited to a surface coating on dry boards; instead, it requires applying treatment agents into the outer layer of wet wood with high moisture content that is actively releasing water. The process selection must be re-evaluated based on this reality.

Mold growth window on wet boards

Typical moisture content in green boards ranges from 60% to 120%, exceeding the fiber saturation point with cell cavities filled with free water. In stacked conditions, insufficient airflow between board surfaces allows Penicillium, Trichoderma, Aspergillus, and blue-stain fungi to develop visible mycelium on the surface within 12–24 hours at temperatures of 25–30℃. Therefore, the essence of anti-mold treatment for green boards is competing with moisture: the biocide must establish an effective concentration on the surface before free water transports the spores there. Waiting until gray-green spots appear on the stacked surface before applying a mold remover means the mycelium has already penetrated the surface, doubling the remediation cost.

Soaking process: Diluted by free water; compensated via concentration and duration.

Immersion involves submerging the entire pallet into a prepared wood preservative solution. While concentration gradients drive the preservative inward, free water within the wet board simultaneously migrates outward, creating a counter-gradient that opposes inward movement. Consequently, the actual penetration depth is lower than in dry boards.

For wet plate scenarios, parameters should be shifted toward higher concentration: dilution ratio 20–30× (vs. the 30–50× commonly used for dry plates), immersion time 60–180 seconds (6–7 seconds longer than dry plates to account for leaching dilution), and liquid temperature maintained between room temperature and 35°C. Verified results show uniform coverage on both sides, with residual chemical concentration at the board's surface approximately 65%–80% of that from dry plate immersion; this single treatment level is sufficient to suppress mold germination.

Species with resin canals, such as pine and larch, exhibit significantly slower chemical diffusion on end grain than on side grain. In wet conditions, the end grain is the primary entry point for mold and blue stain. A dedicated end-grain dip of 30–60 seconds achieves an effective penetration depth of 3–5 mm—surpassing full-board soaking in efficiency. This step is the most frequently skipped during wet board treatment.

The bottleneck remains cycle time. Wet panels carry significant liquid when lifted from the tank, requiring 5–10 seconds for drainage. For a saw table producing one part every 5 seconds, an immersion tank solution is difficult to align with this pace.

Spray Process: Water film impact and adhesion, broken down by pressure and formulation.

The misting system atomizes the anti-mold agent through nozzles and sprays it onto the board surface, relying on impact force and wetting action for adhesion. A visible free water film exists on the wet board surface; when conventional emulsifiable concentrate agents contact this film, they become diluted and are washed away with the water, resulting in insufficient agent residue.

Adjust parameters toward the high-concentration and high-pressure settings: dilute the eco-friendly wood anti-mildew emulsion to 8–15 times (higher than the standard 15–30 times used for dry boards), apply pressure at 0.4–0.6 MPa (one level above that for dry boards to break through the water film), set conveyor speed to 1–2 m/min to extend wet contact time, and ensure 6-sided coverage with at least 90% on each side. For formulation, finer particle-size emulsions with higher surface activity adhere better to wet boards than conventional oil-based agents, forming a continuous layer over the water film.

Wet plate spraying leaves 15%–25% less surface residue than dry plating; this difference can be offset by increasing the concentration. The key advantage is throughput: a fully automated wood anti-mold machine can connect directly to sawing and multi-blade saw exits, handling 3000–5000 units per day without bottlenecking.

The limitation lies in covering geometric blind spots: gaps between panels, surfaces within stacked piles, and inner layers of panel ends—areas where simple spraying cannot reach. For wet-panel scenarios that require no drying, a combined approach of "spraying after sawing + end-dip immersion at the front of stacking" is recommended to prevent mold from forming on the ends first.

Selection recommendations for non-drying scenarios

The single soaking route suits facilities with daily output under 3000 units and space for soaking tanks and drainage zones. For pine, poplar, or larch in medium dimensions (40–60 mm thick), six-sided integrated protection combined with end-grip dipping covers the mold risk window. Equipment investment is about one-third of a spray line.

A single spray line is suitable for scenarios with daily output exceeding 5000 units and uniform panel shapes. When wet contact time is insufficient, edges may lag; therefore, a dedicated edge treatment station must be added.

Combined process: top-spray + end-dip ensures stability in wet-plate, no-dry scenarios. Mu Dun New Materials' solution installs an automated anti-mold machine at the sawing station for six-sided online spraying with eco-friendly anti-mold emulsion, followed by high-concentration dip treatment on end faces before stacking. This two-step approach covers the mold-risk window of 24–48 hours with effective protection.

Apply parameters to your own data

Send three representative wet board samples (freshly cut from the line or randomly sampled from the stack, with moisture content readings) along with the production line layout. Our technical team will conduct tests on surface adhesion, chemical residue, and end-grain diffusion to provide quantitative recommendations for dilution ratio, pressure, line speed, and replenishment cycle. Mold prevention for palletized materials without drying is achieved not by empirical fine-tuning, but by accurately measuring parameters.