What Role Do Surface Additives Play in the Papermaking Process?

Paper quality is often judged by what you can see and feel—smoothness, print clarity, strength, and how the sheet behaves when it meets ink or moisture. Many of these “end-use” properties are decided at the surface, not in the middle of the sheet. That is where surface additives become essential. They are applied after the paper web is formed to fine-tune performance, reduce defects, and help mills meet grade targets with better consistency.

Below you will learn what surface additives do, where they are used in the machine, and why Surface Additives Chemicals are a practical lever for improving paper and board—especially for packaging grades that need strength and protection.

What Are Surface Additives in Papermaking?

Surface additives are chemicals applied to the paper surface—typically at the size press or film press—after the sheet has already been formed and partially dried. Their job is to modify surface behavior such as:

• Water absorption and liquid penetration

• Surface strength (pick resistance, linting control)

• Printability and ink holdout

• Smoothness and surface uniformity

• Barrier performance (moisture, oil/grease, sometimes oxygen)

Unlike internal additives (added in the wet end), surface additives are targeted. They deliver performance where it matters most: the top layer of the sheet.

Why the Paper Surface Needs Chemical Control

Even when the fiber blend and forming conditions are stable, paper can still fail at the surface. Common surface-driven issues include:

• Picking and dusting during printing

• Uneven ink absorption causing dull or patchy prints

• Excessive water uptake leading to loss of stiffness or curl

• Higher coating demand to reach target smoothness

• Converting problems in packaging (scuffing, cracking, weak folds)

Surface Additives Chemicals help solve these problems by creating a more controlled and functional top layer. This is especially relevant when mills are trying to optimize cost, reduce rejects, or upgrade a grade without changing the full furnish.

Where Surface Additives Are Applied in the Paper Machine

Most surface treatment happens after the sheet has gained enough dryness to accept an applied solution without collapsing the structure.

1) Size Press Application

A size press applies a starch or chemical solution to both sides of the sheet as it runs through press rolls. This improves surface bonding and can also add sizing. It is widely used in:

• Writing and printing papers

• Copier and offset grades

• Paperboard and packaging papers needing surface strength

2) Film Press Application

A film press uses metering elements to apply a thin, controlled film of solution. It provides:

• Better control of coat weight

• More uniform application at higher speeds

• Efficient use of chemicals

Both systems enable surface additives to act precisely on the outer layer of the paper, improving performance with relatively low chemical dosage compared to bulk treatments.

Key Functions of Surface Additives

1) Surface Strength Improvement

One of the biggest roles of surface additives is improving surface strength—how well fibers hold together at the top layer. Stronger surfaces reduce:

• Picking on offset presses

• Dusting in digital printing

• Linting during converting

• Sheet damage during high-speed handling

Common strength contributors include starch and polymer-based binders that improve bonding between surface fibers.

2) Water Control and Surface Sizing

Surface sizing reduces uncontrolled liquid penetration. This matters for:

• Print definition and ink holdout

• Reduced feathering and bleeding

• Better resistance to humidity-driven issues

• Packaging papers that face moisture in storage or logistics

Surface sizing can be achieved through starch systems with sizing chemistry, depending on grade needs.

3) Printability and Ink Holdout

Printability is often a balance: paper must accept ink but not allow it to spread or sink too deeply. Surface additives support:

• Sharper dots and cleaner text

• More uniform color density

• Less mottling

• Controlled ink absorption

This is critical for commercial printing, labels, and packaging designs where visual consistency drives customer acceptance.

4) Surface Smoothness and Uniformity

Surface quality is affected by fiber distribution, fines, fillers, and drying. Additives can improve:

• Surface leveling

• Reduced roughness

• Better coating holdout (if coated)

• More consistent sheet appearance

This can reduce the need for heavy coating or help achieve targets with less variability.

5) Functional and Barrier Performance for Packaging

Packaging needs more than printability. It often needs resistance to moisture, oil/grease, or scuffing. That is where packaging surface additives chemical solutions come into play.

Packaging-focused surface treatments can support:

• Moisture resistance for outer liners

• Grease resistance for food wraps

• Improved surface strength for corrugated printing

• Better converting performance (folding, gluing behavior)

Not every grade needs full barrier coating. In many cases, the right packaging surface additives chemical strategy gives meaningful improvements without major process changes.

Types of Surface Additives Commonly Used

Here are practical categories mills use when selecting Surface Additives Chemicals:

Starch-Based Surface Additives

• High impact on surface strength

• Cost-effective

• Used across many grades

• Works well in size press application

Polymer and Binder Systems

• Improve surface bonding

• Enhance strength, holdout, and surface integrity

• Often used to support higher speed and demanding print grades

Surface Sizing Chemistry

• Reduces water penetration

• Helps improve ink holdout

• Useful for uncoated printing grades and packaging papers

Functional Additives for Packaging

• Designed to enhance resistance properties

• Can be tuned for moisture, oil/grease, or rub resistance

• Often selected based on end-use and converting requirements

How Mills Decide Which Surface Additives to Use

Selecting surface additives is not just “add chemical, get result.” Mills usually evaluate based on:

• Paper grade requirements (printing, packaging, board, specialty)

• Machine speed and application method (size press vs film press)

• Target property gaps (strength, absorption, printability, resistance)

• Cost per ton and efficiency (dosage vs improvement)

• Downstream performance (printing, lamination, converting, storage)

A good selection process includes lab trials, machine trials, and measuring property changes such as Cobb value, pick strength, print density, and linting.

Practical Benefits of Surface Additives for Paper Manufacturers

When applied correctly, surface additives help paper mills achieve measurable improvements:

• Better surface strength and reduced printing defects

• Improved print quality and more consistent visual output

• Lower rejection rates and reduced customer complaints

• Higher machine efficiency due to fewer surface-related issues

• Ability to upgrade grades without changing the full furnish

• Better performance in packaging through targeted surface treatment

For packaging producers, a well-chosen packaging surface additives chemical approach can be a strong differentiator—especially when customers demand better durability and performance under real-world handling and moisture conditions.

Common Mistakes to Avoid with Surface Additives

Even strong chemistry can underperform if the process is not controlled. Typical issues include:

• Applying the wrong solids level (too low or too high)

• Poor viscosity control causing uneven film formation

• Inadequate mixing or unstable preparation

• Not matching additive selection to end-use requirements

• Over-correcting one property and damaging another (for example, too much holdout reducing ink acceptance)

Consistent monitoring and small controlled trials usually deliver better outcomes than big “one-shot” changes.

Conclusion

Surface additives play a direct and practical role in the papermaking process by improving the properties that customers notice first: surface strength, printability, and resistance to water or ink. By applying Surface Additives Chemicals at the size press or film press, paper manufacturers can correct surface weaknesses, reduce defects, and optimize quality without rebuilding the entire sheet structure. For packaging grades, a targeted packaging surface additives chemical strategy helps deliver stronger, more reliable performance during converting, storage, and real-world handling. In modern papermaking, surface treatment is not optional—it is a key lever for consistency, efficiency, and product value.