Craters Keep Appearing in Water-Based Coatings? How to Choose the Right Silicone Leveling Agent-Iota

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News > Dynamic industry > Craters Keep Appearing in Water-Based Coatings? How to Choose the Right Silicone Leveling Agent

Craters Keep Appearing in Water-Based Coatings? How to Choose the Right Silicone Leveling Agent

You have already added a leveling agent to your water-based coating, but the craters keep appearing. When the craters are finally eliminated, orange peel develops instead.

You try leveling agents from three or four suppliers. Every product claims to offer “excellent performance,” but the results are inconsistent. Some cause compatibility problems, such as haze or separation. Others improve leveling for only a short time, and the defects return as soon as the coating dries.

Even worse, some leveling agents seriously affect recoating. When the second coat is applied, it pulls away from the edges or even causes intercoat delamination.

In many cases, the problem is not whether the leveling agent is “good” or “bad.” The real issue is whether the selected product matches the coating system and the specific defect.

Water-based coatings generally have much higher surface tension than solvent-based coatings, which makes substrate wetting more difficult. If a leveling agent is selected only by price rather than by technical parameters and formulation compatibility, problems are likely to occur.

As a full-chain silicone solutions provider, Iota Silicone Oil Anhui Co., Ltd. offers a mature range of coating additives. This guide explains how silicone leveling agents work and how to select the right product for water-based coatings.

1. How Silicone Leveling Agents Work: More Than Just Lowering Surface Tension

Many formulators understand leveling agents simply as additives that “reduce surface tension.” In reality, silicone leveling agents influence at least three physical processes in a coating system.

1.1 Reducing surface tension and improving substrate wetting

The surface tension of water-based coatings is typically between 50 and 72 mN/m, significantly higher than the 25–35 mN/m commonly found in solvent-based coatings.

Polyether-modified silicone oils can have a surface tension of approximately 20–25 mN/m. At an addition level of only 0.1–0.5%, they can reduce the overall surface tension of a coating to below 30 mN/m.

When the coating’s surface tension is lower than the critical surface tension of the substrate, the coating can wet and spread more effectively.

Without sufficient wetting, a water-based coating may retract into droplets on low-surface-energy substrates such as plastics or oil-contaminated metal. This often appears as craters, edge pullback or poor coverage.

1.2 Suppressing Bénard cells caused by the Marangoni effect

During film drying, uneven surface tension can create internal convection.

Liquid moves from areas of lower surface tension toward areas of higher surface tension, forming hexagonal circulation patterns known as Bénard cells. After drying, these flow patterns may appear as orange peel or an uneven surface.

After migrating to the coating surface, a silicone leveling agent can form a more uniform low-surface-tension layer. This reduces the surface-tension gradient and helps suppress the formation of Bénard cells.

The product description for IOTA 2H-57 specifically mentions the prevention of Bénard cells, indicating that the product is designed to address this mechanism.

1.3 Providing slip and anti-blocking properties

Polyether-modified silicone oils can form a siloxane-enriched layer on the coating surface, significantly reducing the coefficient of friction.

This not only improves surface feel and slip but can also help prevent blocking during the early stages of film drying.

The TDS for IOTA 2H-810 specifies an additional anti-blocking effect. IOTA 2520H goes a step further: its hydroxyl functional groups can participate in crosslinking, providing durable slip with reduced migration.

Once these three mechanisms are understood, the selection logic becomes much clearer. The goal is not to choose the “strongest” leveling agent, but the product that best matches the coating defect:

For craters, prioritize substrate wetting.
For orange peel, prioritize flow and leveling.
For surface feel, prioritize slip modification.
For pinholes, review defoaming and air release as well.

2. How to Select a Silicone Leveling Agent for Water-Based Coatings: A Three-Step Method

Before selecting a product, first identify the actual defect in the coating. The following three-step method can help narrow down the appropriate product quickly.

Step 1: Identify the type of coating defect

Flow and leveling defects in water-based coatings generally appear in four main forms:

Crater: A circular depression in the coating film
Orange peel: A wavy or textured surface resembling orange skin
Pinhole: A small hole usually left after a bubble ruptures
Edge creep or edge pullback: Retraction of the coating from the edge of the substrate

Craters and edge pullback are often associated with inadequate wetting caused by an excessively high surface tension. A wetting-type additive should therefore be evaluated first.

Orange peel is often related to surface-tension gradients during drying. In this case, a leveling-type additive is usually more suitable.

Pinholes are frequently connected with foam, entrained air, solvent or water release, and drying conditions. They may require adjustment of the defoamer or air-release additive rather than simply adding more leveling agent.

Step 2: Confirm compatibility with the water-based system

The key parameters for a water-based system include water solubility, dispersibility and cloud point.

The water solubility of a polyether-modified silicone oil depends on the proportion and structure of its polyether segments:

EO segments generally improve water solubility.
PO segments can influence hydrophobicity, foam control and compatibility.

IOTA 245 is a water-soluble, polyether-modified silicone oil with a cloud point of 50–60°C. This means it has good water solubility at room temperature but may become cloudy in systems processed or stored at higher temperatures.

If the formulation requires greater stability across a wide temperature or pH range, IOTA 2141F may be considered. It is an anionic silicone surfactant that remains stable from pH 2 to 12 and contains no APEO.

Step 3: Match the addition level with actual active content

Different leveling agents have different active contents, which directly affects the actual cost per kilogram of finished coating.

The following table compares five commonly used IOTA products.

Product	Viscosity at 25°C	Active content	Recommended dosage in water-based systems	Main advantage
IOTA 2H-850	50–150 mm²/s	100%	0.05–0.3%	High compatibility, recoatability and scratch resistance
IOTA 2H-810	200–1,000 mm²/s	100%	0.05–0.5%	Efficient crater elimination and anti-blocking
IOTA 2H-57	40–200 mm²/s	≥95%	0.3–1.0%	Suppression of Bénard cells and improved gloss
IOTA 245 wetting agent	10–100 cP	>99.8%	0.1–0.5%	Water-soluble, low surface tension and crater prevention
IOTA 2141F anionic surfactant	100–200 cP	77 ± 2%	0.1–1.0%	Surface tension of 21 dyn/cm and stability from pH 2 to 12

The selection logic is straightforward.

If cratering is the main problem in a water-based coating, start by evaluating IOTA 245 or IOTA 2141F. Both provide good water compatibility and can rapidly reduce surface tension, making them suitable for craters caused by inadequate substrate wetting.

If the main problems are orange peel and insufficient leveling, evaluate IOTA 2H-850 or IOTA 2H-810. Both are 100% active leveling agents with relatively low recommended addition levels.

If the coating has both orange peel and uneven gloss, IOTA 2H-57 may be the better option because it is specifically designed to suppress Bénard cells.

3. Why More Leveling Agent Is Not Always Better

A common formulation mistake is assuming that a higher dosage will produce better leveling.

Using IOTA 2H-850 as an example, an addition level above 0.3% in some water-based systems may begin to cause compatibility problems, including film haze and reduced gloss.

IOTA 2H-57 has an active content of at least 95%, but its recommended addition level is 0.3–1.0%. This indicates that it should be used within an appropriate concentration range to achieve its intended effect.

A more reliable method is to begin around the middle of the TDS-recommended dosage range and then adjust gradually according to the test panel results.

The final dosage should be confirmed through drawdowns or spray-panel tests. Key properties to evaluate include:

Crater elimination
Leveling
Gloss
Haze
Foam stability
Intercoat adhesion
Recoatability
Slip
Scratch resistance

4. IOTA Leveling Agent Product Range and Technical Data

IOTA offers a complete water-based coating additive range, covering substrate wetting, flow and leveling, slip modification and surface performance control.

The following technical data are based on published product TDS information.

IOTA 2H-850

IOTA 2H-850 is a polyether-modified siloxane leveling agent.

Main technical parameters:

CAS number: 157479-55-5
Appearance: Colorless to pale-yellow liquid
Viscosity at 25°C: 50–150 mm²/s
Active content: 100%
Density: 1.01–1.04 g/cm³
Refractive index: 1.40–1.46
Recommended dosage in water-based systems: 0.05–0.3%

It is suitable for water-based, solvent-based and UV-curable systems. It is particularly recommended for water-based wood coatings and industrial coatings.

Its main advantages are high compatibility, a very low risk of causing haze and minimal influence on recoatability.

IOTA 2H-810

IOTA 2H-810 is a high-efficiency silicone-based leveling agent.

Main technical parameters:

CAS number: 128192-17-6
Viscosity: 200–1,000 mm²/s
Active content: 100%
Recommended dosage: 0.05–0.5%
Maximum dosage in certain printing inks: Up to 1.0%

Compared with IOTA 2H-850, IOTA 2H-810 has a higher viscosity and larger molecular structure. It can provide a more persistent leveling effect and additional anti-blocking performance.

IOTA 2H-57

IOTA 2H-57 is a silicone leveling agent designed to improve flow, gloss and surface uniformity.

Main technical parameters:

CAS number: 70914-12-4
Viscosity at 25°C: 40–200 mm²/s
Active content: At least 95%
Density: 1.01–1.03 g/cm³
Recommended dosage in water-based systems: 0.3–1.0%

Its main function is to suppress Bénard cells caused by surface-tension gradients during film formation. It is suitable for systems showing orange peel, uneven gloss or poor surface flow.

IOTA 245

IOTA 245 is a water-soluble, polyether-modified silicone wetting agent developed for water-based systems.

Main technical parameters:

Active content: More than 99.8%
Viscosity: 10–100 cP
Density: 1.025–1.049 g/cm³
Cloud point: 50–60°C
Water solubility: Soluble in water
Recommended dosage: 0.1–0.5%

It shows good compatibility with water-based polyurethane, water-based acrylic and water-based alkyd resin systems.

IOTA 245 is an entry-level option for addressing craters caused by inadequate substrate wetting in water-based coatings.

IOTA 2141F

IOTA 2141F is an anionic silicone surfactant.

Main technical parameters:

Solid content: 77 ± 2%
Viscosity: 100–200 cP
Surface tension: 21.0 ± 2.0 dyn/cm in a 0.1% aqueous solution
Stable pH range: 2–12
APEO content: APEO-free
Recommended dosage: 0.1–1.0%

It is suitable for water-based coatings and inks with strict environmental and formulation-stability requirements.

5. Comparison of IOTA Leveling and Wetting Agents

The following table compares the main technical parameters of five IOTA coating additives.

Parameter	IOTA 2H-850	IOTA 2H-810	IOTA 2H-57	IOTA 245	IOTA 2141F
Product type	Leveling agent	Leveling agent	Leveling agent	Wetting agent	Anionic surfactant
CAS number	157479-55-5	128192-17-6	70914-12-4	Not specified	Not specified
Active content	100%	100%	≥95%	>99.8%	77 ± 2%
Viscosity at 25°C	50–150 mm²/s	200–1,000 mm²/s	40–200 mm²/s	10–100 cP	100–200 cP
Density	1.01–1.04 g/cm³	1.01–1.04 g/cm³	1.01–1.03 g/cm³	1.025–1.049 g/cm³	Not specified
Water compatibility	Dispersible	Dispersible	Dispersible	Water-soluble	Soluble
Recommended dosage in water-based systems	0.05–0.3%	0.05–0.5%	0.3–1.0%	0.1–0.5%	0.1–1.0%
Recoatability	No significant influence	No significant influence	Good	No significant influence	Good
Shelf life	12 months	12 months	12 months	12 months	24 months

Several important differences can be identified from the comparison.

First, IOTA 2H-850 and IOTA 2H-810 both have 100% active content. They can be added without introducing additional carrier solvents, which is particularly important for water-based coatings with low-VOC targets.

Second, the viscosity range extends from 10 cP for IOTA 245 to 1,000 mm²/s for IOTA 2H-810. This covers applications ranging from rapid substrate wetting to longer-lasting flow and leveling.

Third, IOTA 2141F provides a surface tension of approximately 21 dyn/cm in a 0.1% aqueous solution. This gives it a particular advantage on difficult-to-wet substrates, such as plastic films and metal surfaces contaminated by trace oils.

6. Application Examples

IOTA 2H-850 has been used in water-based wood coatings, water-based industrial coatings and water-based automotive coatings.

In a typical water-based acrylic wood coating formulation, adding 0.15% IOTA 2H-850 can help eliminate craters associated with substrate contamination while maintaining good recoatability.

In a water-based polyurethane leather coating, a combination of 0.3% IOTA 245 and 0.2% IOTA 2520H can improve substrate wetting, reduce cratering and provide a durable, smooth surface feel.

In a water-based ink system, IOTA 2141F used at 0.5% can provide effective spreading and leveling on paper, plastic and metal substrates. It remains stable across a broad pH range of 2–12.

These examples are formulation references rather than universal dosage guarantees. The final dosage should be confirmed according to the resin, pigment system, substrate, application method and drying conditions.

7. Frequently Asked Questions

What causes craters in water-based coatings?

Craters can be caused by poor substrate wetting, local contamination, foam, incompatible additives or uneven surface tension. The defect should be diagnosed before selecting a leveling or wetting agent.

Which additive should be used for craters in water-based coatings?

If the craters are caused by inadequate substrate wetting, a water-compatible wetting agent such as IOTA 245 or IOTA 2141F may be evaluated first.

Which silicone leveling agent is suitable for orange peel?

Orange peel is often related to uneven flow and surface-tension gradients during drying. IOTA 2H-850, IOTA 2H-810 or IOTA 2H-57 may be evaluated, depending on the resin system and the severity of the defect.

Can a leveling agent also eliminate pinholes?

Not necessarily. Pinholes are often related to foam, trapped air, water or solvent release, and drying speed. A defoamer or air-release additive may also be required.

Does a silicone leveling agent affect recoatability?

It can. An excessive dosage or a poorly compatible silicone additive may migrate to the coating surface and interfere with intercoat wetting or adhesion. Recoatability should always be included in the formulation test.

How much silicone leveling agent should be added?

The dosage depends on the product’s active content, the resin system and the coating defect. A practical approach is to begin near the middle of the recommended TDS range and then adjust gradually through panel testing.

8. Need Technical Support?

Selecting a leveling agent cannot be completed by reading a single article. The final result is affected by the resin system, substrate, application method—such as spraying, roller coating or curtain coating—and drying conditions.

For an accurate product recommendation, provide the following information: