What Is a Surface Sizing Agent?
A surface sizing agent is a functional chemical applied to the surface of paper or board to enhance its water resistance, surface strength, printability, and appearance. Unlike internal sizing—which is added during the wet-end process—surface sizing is applied via a size press after sheet formation but before drying.
This layer forms a protective film on the surface of the paper, reducing water and ink penetration while improving surface cohesion. It is especially important in high-speed printing and packaging applications, where dimensional stability and surface strength are critical.
Common Types of Surface Sizing Agents
Several types of surface sizing agents are commonly used, each offering different performance characteristics:
1. Oxidized Starch
- Derived from corn or tapioca, this is the most economical and widely used surface sizing material.
- Benefits: Improves surface strength and ink holdout.
- Limitation: Limited water resistance, may require modification or blending.
2. AKD Emulsion (Alkyl Ketene Dimer)
- A reactive sizing agent that bonds chemically with cellulose fibers.
- Benefits: Excellent water repellency and improved sizing uniformity.
- Used when greater hydrophobicity is needed in surface sizing, such as in food-grade packaging papers.
- Explore our AKD Sizing Agent →
3. Synthetic Polymers (Styrene–Acrylic, PVOH, etc.)
- Tailored for specialty needs such as high gloss, wet rub resistance, or print receptivity.
- Benefits: Customizable film-forming properties, ideal for coated boards and inkjet printing.
Applications Across Paper Grades
Surface sizing agents are used in a broad range of paper and board types:
- Packaging Grades (e.g. carton board, kraft liner): Improve water resistance, rigidity, and print surface quality.
- Cultural & Writing Paper: Provide ink holdout, smoothness, and reduced feathering for fountain pen or inkjet use.
- Corrugated Base Paper: Enhance surface strength to resist abrasion and fiber picking during converting.
- Industrial Grades: Help resist chemical or moisture exposure for specialty barrier applications.
Synergy with Internal Sizing and Barrier Agents
Surface sizing works best when paired with other wet-end and coating solutions:
- Internal Sizing (e.g., AKD or ASA): Provides bulk hydrophobicity, while surface sizing reinforces water repellency and controls ink penetration.
- Fluorine-Free Oil Repellents: When used in the size press, these agents can provide both grease resistance and liquid barrier properties for food-contact paper.
- Pigment Coatings: A good surface sizing layer can improve coating holdout and prevent binder penetration into the base sheet.
By combining solutions, papermakers can tailor performance for specific end-use requirements.
Choosing the Right Surface Sizing Agent
When selecting a surface sizing agent, consider the following factors:
| Requirement | Recommended Agent |
|---|---|
| Basic printability & surface strength | Oxidized starch |
| Water repellency for packaging | AKD emulsion or synthetic polymers |
| High-speed inkjet printing | PVOH-based polymers or modified starch blends |
| Grease/oil resistance | Fluorine-free barrier sizing agent |
Proper agent selection and application dosage depend on paper grade, machine speed, pH range, and the desired surface properties.
Enhance Your Paper Performance with Amazon Chemicals
At Amazon Chemicals, we offer a full range of surface sizing solutions—from cost-effective starch-based systems to advanced polymer blends—for packaging, cultural paper, and specialty grades.
Our team can help you:
- Choose the right sizing formula for your application
- Balance cost, performance, and regulatory needs
- Integrate with internal sizing and barrier treatments
👉 Let’s optimize your paper surface together.
Contact us for technical advice or browse our surface sizing products.
