If you are standing in front of two lamination machines and trying to decide which one to buy — or if you are a print buyer trying to understand why two suppliers gave you completely different quotes for the same job — the first thing to understand is that not all lamination is the same. There are two fundamentally different technologies at play, and they produce results that look similar but behave differently.
Thermal lamination uses a pre-coated film. The adhesive — typically an EVA (ethylene-vinyl acetate) copolymer — is already applied to the back of the film at the factory. When this film passes through the heated roller of a thermal laminator, the adhesive melts, becomes fluid, and bonds to the paper as it cools under pressure. It is a dry process: no solvents, no water, no mixing, no curing time. The film comes off the roll ready to use.
Wet lamination uses liquid adhesive. The adhesive — usually a water-based acrylic or polyurethane dispersion — is applied to the film or paper by the machine itself, then dried before the two layers are pressed together. It is a wet-then-dry process: the water must be evaporated completely before lamination happens, or the trapped moisture will create defects.
The thermal process is faster. Because there is no drying step, thermal laminators can run at 30 to 80 meters per minute on a typical production line, and high-end machines exceed 120 m/min. Wet laminators are limited by how fast the drying tunnel can evaporate water, which typically caps them at 20 to 40 m/min for water-based adhesives. For a print shop running thousands of sheets per day, this speed difference translates directly into capacity and labor cost.
But speed is not the whole story. The finished look and feel differ in ways that matter for certain applications. Thermal lamination produces a distinct plastic feel — the film adds noticeable thickness and rigidity to the sheet because the EVA adhesive layer itself is typically 12 to 18 microns thick, on top of the 15 to 20 micron film. The result is a stiff, glossy, highly protective surface that excels on book covers, menus, shopping bags, and packaging boxes where durability is the priority.
Wet lamination produces a more natural paper feel. The adhesive layer is much thinner — typically 3 to 5 microns dry — so the film sits closer to the paper surface. The finished product bends more like uncoated paper and feels less like a plastic card. This is why wet lamination is preferred for high-end art books, photography portfolios, and luxury packaging where the tactile experience matters as much as the visual.
We work with printers across a wide range of market segments, and one thing that surprises many newcomers is how strongly end customers react to the feel of a laminated product. A publisher ordering a coffee table book wants it to feel like paper, not like a cafeteria menu. A restaurant chain ordering menus wants exactly the opposite — they want something that can survive spilled drinks and daily handling. The choice between thermal and wet lamination is really a choice about what kind of physical experience you want to create.
The durability difference is worth understanding in detail. Thermal lamination adhesive forms a continuous polymer film when it cools, which acts as a barrier layer independent of the BOPP or PET film. Wet lamination adhesive penetrates slightly into the paper fibers before drying, creating a mechanical interlock as well as a chemical bond. Both bonds are strong, but they fail differently. Thermal lamination tends to delaminate in sheets — you can peel the entire film off in one piece if the bond fails at the edge. Wet lamination tends to bond more integrally; if you try to peel it, paper fibers come with the film.
Cost structure is another key differentiator. Thermal lamination film is more expensive per square meter because the adhesive coating step adds manufacturing cost at the film factory. However, the machine itself is simpler — no coating station, no drying tunnel, no adhesive mixing and cleaning — which means lower machine cost and less maintenance. Wet lamination uses cheaper plain film and liquid adhesive, but the machine is more complex, and the ongoing cost of adhesive, cleaning solvents, and drying energy consumption can be higher in the long run.
Environmental considerations have become a deciding factor for many buyers. Thermal lamination uses no VOCs (volatile organic compounds) because there are no liquid solvents. It is a clean process from an air quality standpoint. Wet lamination with water-based adhesives is also low-VOC, but solvent-based wet lamination — still used in some industrial applications — requires solvent recovery or incineration systems. Both thermal and water-based wet lamination can be considered environmentally preferable, but they handle differently at end-of-life. A thermally laminated sheet is harder to de-ink in the paper recycling process because the plastic film and thick adhesive layer must be separated from the paper fibers.
The application sweet spots are clear. Thermal lamination dominates in book covers, commercial print finishing, packaging boxes, shopping bags, and anything that needs high-volume, high-speed production with robust protection. Wet lamination dominates in premium publications, luxury packaging, flexible packaging with high bond-strength requirements, and applications where the final product must remain flexible rather than stiff.
Some converters run both technologies side by side, choosing the machine based on the job. The trend in recent years has been toward thermal lamination for the majority of commercial work due to its speed and simplicity, with wet lamination reserved for specialty applications where the premium feel or higher bond strength justifies the slower process.
The bottom line is this: thermal lamination is about efficiency, wet lamination is about aesthetics and bond depth. Neither is better in absolute terms — they are better for different things. Understanding which one fits your product is the first and most important decision in the lamination process.
Frequently Asked Questions
Can I use the same film roll in both thermal and wet lamination?
No. Thermal lamination requires film pre-coated with heat-activated adhesive. Wet lamination uses plain, uncoated film because the adhesive is applied by the machine. Using the wrong film type will either fail to bond (plain film in a thermal machine) or gum up your rollers (pre-coated film in a wet machine).
Which lamination method is cheaper per square meter?
For short runs (under 1,000 sheets), thermal lamination is usually cheaper because setup is faster and there is no adhesive mixing or drying time. For very long runs (tens of thousands of identical sheets), wet lamination can become cheaper because the consumable cost (plain film + bulk adhesive) is lower per square meter, offsetting the higher machine and labor cost.
Does thermal lamination work on all paper types?
Thermal lamination works well on most coated papers but can struggle with highly absorbent uncoated papers. The melted adhesive can be drawn into the paper pores before it has time to bond to the film surface, resulting in weak adhesion. For very porous papers, wet lamination often produces a better result because the liquid adhesive can penetrate slightly and create a mechanical bond.
Why does wet lamination film look less glossy than thermal?
In wet lamination, the adhesive layer is extremely thin (3-5 microns), so the film sits closer to the paper surface and follows the paper's natural micro-texture more closely. In thermal lamination, the thicker adhesive layer (12-18 microns) acts as a smoothing filler, creating a flatter surface that reflects light more uniformly — hence the higher perceived gloss.
Can I switch a thermal laminator to wet lamination?
No, the two technologies require fundamentally different machine architectures. A thermal laminator lacks a coating station, drying tunnel, and adhesive circulation system. A wet laminator's heated roller is designed for lower temperatures than a thermal machine's. These are different machines built for different processes — they cannot be converted from one to the other.
Which method produces better adhesion on synthetic papers?
Wet lamination generally produces better adhesion on synthetic papers (like Yupo or Teslin) because the liquid adhesive can be formulated with additives that improve bonding to plastic surfaces. Thermal lamination's EVA adhesive is optimized for natural cellulose fibers and may produce inconsistent results on synthetic substrates. Always test before committing to a full production run.
This article draws on the hands-on production experience of the technical team at Shandong Shunzhan New Materials Co., Ltd., where we have been manufacturing BOPP and PET functional films for over two decades. Our films are used by packaging converters, printers, and label manufacturers in more than 50 countries — from the Middle East to Southeast Asia to Australia.
If you found this article helpful and have a specific film selection or processing question, we are happy to share what we know. Reach out for a technical consultation or sample evaluation.
热覆膜 vs. 湿覆膜：两种方式，两种效果
如果你站在两台覆膜机前试图决定买哪一台 — 或者如果你是一个印刷采购，试图理解为什么两个供应商对同一个活给出了完全不同的报价 — 首先要理解的是，并非所有覆膜都是一样的。有两种根本上不同的技术，它们产生看起来相似但表现不同的结果。
热覆膜使用预涂膜。胶水 — 通常是EVA（乙烯-醋酸乙烯酯）共聚物 — 已经在工厂预涂在薄膜背面。当这种薄膜通过热覆膜机的加热辊时，胶水熔化、变成液态，在压力下冷却时粘合到纸张上。这是一个干式过程：无溶剂、无水、无需混合、无需固化时间。薄膜从卷上取下来就能用。
湿覆膜使用液体胶水。胶水 — 通常是水性丙烯酸或聚氨酯分散液 — 由机器本身施加到薄膜或纸张上，然后在两层压合之前干燥。这是一个先湿后干的过程：水必须在覆膜发生之前完全蒸发，否则残留的水分会产生缺陷。
热覆膜工艺更快。因为没有干燥步骤，热覆膜机在典型生产线上的运行速度为30到80米每分钟，高端机器超过120 m/min。湿覆膜机受限于干燥通道蒸发的速度，对于水性胶水通常上限为20到40 m/min。对于一个每天运行数千张纸的印刷车间，这种速度差异直接转化为产能和人工成本。
但速度不是全部。成品的外观和触感以对某些应用很重要的方式存在差异。热覆膜产生明显的塑料感 — 薄膜为纸张增加明显的厚度和刚性，因为EVA胶层本身通常有12到18微米厚，在15到20微米薄膜之上。结果是一个硬挺、光亮、高度保护的表面，非常适合书封、菜单、购物袋和包装盒等以耐用性为首要考虑的应用。
湿覆膜产生更自然的纸张触感。胶层要薄得多 — 通常干膜只有3到5微米 — 所以薄膜更贴近纸张表面。成品弯曲起来更像无涂层纸张，摸起来不像塑料卡片。这就是为什么湿覆膜在高端画册、摄影作品集和奢侈品包装中更受青睐，这些场景中触觉体验和视觉效果同样重要。
我们与覆盖广泛市场细分的印刷商合作，发现让许多新人感到惊讶的一件事是终端客户对覆膜产品触感的反应有多么强烈。订购咖啡桌画册的出版商希望它摸起来像纸，而不是像食堂菜单。而订购菜单的连锁餐厅则恰恰相反 — 他们希望产品能经受住溢出饮料和日常拿放的考验。热覆膜还是湿覆膜的选择，实际上是你想创造什么样的物理体验的选择。
耐用性差异值得详细了解。热覆膜胶水在冷却时形成连续的聚合物薄膜，作为独立于BOPP或PET薄膜的阻挡层。湿覆膜胶水在干燥前轻微渗入纸张纤维，既产生机械互锁也产生化学键。两种粘合都很牢固，但失效方式不同。热覆膜倾向于成片脱层 — 如果边缘粘合失败，你可以整张撕下薄膜。湿覆膜倾向于更整体地粘合；如果你试图撕开，纸纤维会随薄膜一起脱落。
成本结构是另一个关键区分。热覆膜膜每平方米更贵，因为涂胶步骤在薄膜工厂增加了制造成本。然而，机器本身更简单 — 无涂布站、无干燥通道、无胶水混合和清洗 — 这意味着更低的机器成本和更少的维护。湿覆膜使用更便宜的裸膜和液体胶水，但机器更复杂，并且胶水、清洗溶剂和干燥能耗的持续成本从长远来看可能更高。
环保考量已成为许多买家的决定性因素。热覆膜不使用VOC（挥发性有机化合物），因为没有液体溶剂。从空气质量角度来看是一个清洁过程。水性胶水的湿覆膜也是低VOC的，但溶剂型湿覆膜 — 仍用于某些工业应用 — 需要溶剂回收或焚烧系统。热覆膜和水性湿覆膜都可以被视为环保优选方案，但它们在产品生命周期末期的处理方式不同。热覆膜的纸张在造纸回收过程中更难脱墨，因为塑料薄膜和厚胶层必须与纸纤维分离。
应用的最佳领域很清楚。热覆膜主导了书封、商业印刷后加工、包装盒、购物袋，以及任何需要大批量、高速生产和强力保护的产品。湿覆膜主导了高端出版物、奢侈品包装、高粘合强度要求的软包装，以及成品必须保持柔软而非僵硬的应用。
一些加工商两种技术并排运行，根据作业选择机器。近年来的趋势是大多数商业作业使用热覆膜，因其速度和简单性，湿覆膜保留用于那些高级触感或更高粘合强度使较慢工艺物有所值的特殊应用。
一句话总结：热覆膜关乎效率，湿覆膜关乎美学和粘合深度。没有哪一种在绝对意义上更好 — 它们在不同方面更好。理解哪一种适合你的产品是覆膜过程中第一个也是最重要的决定。