What Is Wet-Press Molding?

Wet-press molding is a process in which formed, moist pulp is sandwiched between heated molds and dried under pressure. Pressing against the mold surface tightly compacts the fibers, resulting in a smooth, uniform surface finish.

Compared to dry-press molding (a process closer to natural drying) using the same pulp mold, wet-press molding produces less surface roughness and a clean-looking appearance even in white, making it suitable for applications where the ‘unboxing texture’ matters, such as cosmetics, precision equipment, and premium gifts.

Key Points to Consider During Design

A good rule of thumb is a draft angle of at least 3 degrees per side, with a larger angle for deeper items. Insufficient draft causes the product to be pulled during demolding, resulting in surface fuzzing or deformation.

Corner radii matter for both product protection and yield. Sharp corners with an R2 or smaller make it difficult for fibers to wrap around, thinning the wall and reducing strength, so R3–R5 is recommended.

The standard wall thickness is 0.8–1.5mm. A thicker wall increases strength but extends drying time, directly impacting cost, so a design that reinforces rigidity with ribs or raised shapes is effective.

Cost and Adoption Decisions

Wet-press molding requires molds on both the upper and lower sides, and the drying process is longer, resulting in higher initial costs and unit prices than dry-press molding. On the other hand, the appearance quality is clearly superior, so we recommend making the decision with the contribution to brand value in mind.

If you want surface quality but wet-press is difficult within your budget, there are also intermediate options such as semi-dry and semi-wet processes using virgin pulp. We will propose the optimal process based on your budget.

Comparison with Dry-Press Molding

Another representative pulp molding process is dry-press molding, which presses dried pulp into shape in a short time. It differs greatly from wet-press molding in both surface texture and cost structure. The main differences are summarized below.

Comparison Item	Wet-Press	Dry-Press
Draft angle	0.5°+	3°+
Wall thickness	0.7–1.2mm	1.5–2.5mm
Density	0.60–0.70g/cm³	0.35–0.40g/cm³
Main material	Virgin pulp, non-wood pulp	Recycled corrugated cardboard
Surface smoothness	◎	△
Price	△	○
Mold cost	△	○
Surface burst strength	◎	△
Cushioning	△	○

* Depending on the shape (depth, corner complexity, etc.), the draft angle may not always be achievable within the guideline values above. Please contact us for details.

Advantages of Wet-Press
Using virgin pulp or non-wood pulp and pressing firmly with heated molds, wet-press molding achieves high surface smoothness and surface burst strength (◎ rating), and the draft angle can be designed as shallow as 0.5° per side. This makes it easier to reproduce fine embossed logos, sharp edges, and deep shapes, making it well suited to applications such as cosmetics, precision equipment, and premium gifts, where visual texture is directly tied to brand value.

Disadvantages of Wet-Press
Because the density is relatively high at 0.60–0.70g/cm³, cushioning performance (impact absorption) is somewhat inferior to dry-press. Also, since molds are needed on both the upper and lower sides and the drying process is longer, price and mold cost tend to be higher — a drawback to keep in mind.

Advantages of Dry-Press
Using recycled materials such as corrugated cardboard as the main raw material, and with a lower density of 0.35–0.40g/cm³ that contains more air, dry-press molding offers excellent cushioning (○ rating). Because dried pulp is pressed in a short time, productivity is high, and price and mold cost can be kept low (○ rating), making it well suited to applications such as cushioning materials for home appliances and large-volume production runs where cost optimization matters.

Disadvantages of Dry-Press
Because of the mold release requirement, a larger draft angle of 3° or more per side is needed, making it harder to reproduce sharp edges or deep designs. Wall thickness also tends to be greater, at 1.5–2.5mm, compared to wet-press, and surface smoothness and surface burst strength are inferior to wet-press (△ rating).

How to Choose
We recommend weighing three factors when deciding between wet-press and dry-press: “budget,” “quality requirements,” and “visual finish (design).” If unboxing texture and brand image are a priority and there is some budget flexibility, wet-press is the better fit; if the priority is keeping cost down while prioritizing functional aspects such as cushioning, dry-press is the better fit. In actual projects, it is also common to combine both within a single product — for example, using wet-press for the outer shell and dry-press for the internal cushioning structure.

Which process is best depends on the product’s shape, expected quantity, and budget. We also welcome consultations from the drawing or prototype stage, so please feel free to contact us if you are deciding between wet-press and dry-press.

In recent years, “semi-wet, semi-dry press” molding — which aims to combine the high-quality texture of wet-press with the cost and productivity advantages of dry-press — has been attracting attention. It requires advanced mold design, but is increasingly chosen by those who prioritize a balance of cost and quality. For more details, please also see this article.