Organoclay: Oil Paint Additive for Thixotropy and Stability

Organoclay is a rheological additive based on organically modified bentonite clay, widely used in oil and alkyd paint formulations to modify viscosity, improve brush handling, and reduce pigment settling. Designed for easy incorporation, this additive is engineered to provide controlled shear-thinning flow behavior in low- to medium-polarity non-aqueous formulations. Its primary function is to enhance storage stability and sag resistance in systems such as industrial coatings, adhesives, and printing inks.

Thanks to its optimized structure, this organoclay disperses more easily than conventional rheological additives, offering production flexibility and efficient thickening performance without necessarily requiring polar activators.

We selected one type of commercial organoclay as most suitable for artists own use to amend their oil paint. The organoclay sold by Natural Pigments is an organic derivative of bentonite clay. It is very easily dispersed in oil and alkyd-based paints (mediums composed primarily of aliphatic and other non-polar to medium-polarity substances). It can be added at any point in the paint making process and can be used as a post-additive on the painter’s palette. It increases the viscosity of paint, helping it hold its shape and preventing the settling of pigments and fillers.

It is an effective rheological additive that adds thixotropic properties to paint, helping to maintain the shape of brushstrokes and can be used as a substitute for wax and stearates to prevent paint from separating.

It does not require any preparation, such as the preparation of pregels, and does not require chemical activators, unlike some organoclays. It can be added as a powder directly to oil or alkyd vehicles or the finished paint.

Origin and History

Organoclays were first introduced in the mid-20th century for stabilizing drilling fluids and have since been adopted across various industries. Recent advancements in organoclay technology have improved performance characteristics, making them easier to disperse and more adaptable to non-aqueous systems used in modern industrial formulations.

Source

This organoclay is produced by modifying naturally occurring bentonite clay with organic quaternary ammonium compounds. This process enhances the clay’s compatibility with organic solvents by rendering it organophilic. The result is a cream-beige powder that is easily dispersible and highly effective in providing viscosity control.

Applications

Organoclay is suitable for a wide range of non-aqueous applications:

• Oil and Alkyd Paints: Artists can add organoclay to handmade or commercial paints to increase viscosity and impart thixotropy, improving brush handling and preventing pigment settling during storage.

• Coatings: Offers sag resistance and anti-settling for solvent-based coatings.

• Adhesives: Enhances vertical hold and spread control.

• Inks: Improves pigment suspension and overall formulation stability.

• Sealants and Other Industrial Fluids: Controls flow characteristics and prevents phase separation.

Benefits

• Easy Dispersibility: Simplifies processing without the need for high-shear equipment or activators.

• Shear-Thinning Behavior: Enhances application and leveling properties, allowing paint to respond dynamically to brush or knife pressure. This property enables smooth, expressive brushwork and controlled impasto effects while maintaining form when undisturbed on the palette or canvas.

• Anti-Settling Properties: Improves shelf-life and storage performance, which is especially important for artists who make their own paints or store handmade mixtures for extended periods. By reducing pigment sedimentation, organoclay helps maintain uniform consistency over time, minimizing the need for re-mixing and ensuring color integrity and workability straight from the container.

• Production Flexibility: Suitable for both pigment grind and post-addition. This is particularly useful for artists who make their own oil or alkyd paints, as it allows organoclay to be incorporated during the pigment dispersion phase for enhanced stability or added later to adjust flow properties without disrupting the mixture. This flexibility supports custom formulation and precise control over the paint’s working characteristics.

• No Need for Polar Activators: In many systems, the organoclay can function effectively without polar activators—additives such as methanol, propylene carbonate, or ethanol that are traditionally used to aid in the delamination of clay particles. For artists who make their own paints or mediums, this means fewer required ingredients and a simpler workflow. It allows for direct incorporation into the paint without the need for additional solvents, thereby reducing preparation time and minimizing potential alterations to color and drying behavior.

How to Use

Due to its lipophilic properties, organoclay can be used to remove oil from water, and is used in water treatment systems.

Organoclay is readily dispersible for non-polar to medium-polarity organic applications. It may be added at any point in the paint-making process, using all standard paint-making equipment. This rheological additive can be incorporated into the pigment grind under both high shear and low shear conditions. A chemical activator is not required to disperse the organoclay in conventional solvent containing paints.

It can be added to the pigment grind or by mixing rather than grinding. It does, however, require some minimal shear (minimum tip speed of 4 meters per second when a high-speed mixer is used). The liquid paint to which it is to be added should well stirred as it is sifted in. Sufficient time for full activation should be allowed. The amount of time required will depend on the amount of paint, the type and speed of the mixer in use, and the viscosity and solids of the system. When grinding with the pigment, it is not sensitive to high temperatures and no minimum temperature is required.

Making Paint: Add the cream-colored powder to the oil before adding the oil to the pigment. Stir it into the oil, using about 2 to 5% of the total weight of the paint. Grind the mixture thoroughly on a flat surface with a muller to build viscosity and thixotropic properties. Allow the paint to rest for one or more hours before use.

Adding to Paint: Add the cream-colored powder to the paint using a palette knife or spatula, incorporating approximately 2 to 5% of the total paint weight. It is highly recommended to grind the paint thoroughly on a flat surface with a muller to build viscosity and thixotropic properties. Allow the paint to rest for a short time before use.

The manufacturer states that “the best rheological performance under letdown conditions is achieved when the system temperature is between 21 °C (70 °F) and 35 °C (95 °F). When used in the pigment grind, it is not sensitive to high temperatures and no minimum temperature is required.

Toxicity

This organoclay is not classified as hazardous under current EU and OSHA regulations. It should still be handled using standard safety protocols for fine powders, including adequate ventilation and respiratory protection to avoid inhalation of dust. For comprehensive health and safety information, refer to the product's Safety Data Sheet (SDS).

Product Highlights

• Organoclay-based rheological additive for non-aqueous systems

• Provides excellent sag resistance and anti-settling behavior

• Compatible with coatings, adhesives, and ink formulations

• Requires no polar activator in most applications, making it especially well-suited for artist studios where simplicity and control are critical. Whether formulating from raw pigments or adjusting commercial tube paints, artists can benefit from a streamlined workflow without the need for additional chemical additives.

• Long shelf life of 48 months in unopened containers

Storage Recommendations

Store in a cool, dry location.

Shelf Life Life

This product has a shelf life of four years from the date of manufacture.

¹ For artists preparing oil or alkyd paints, this corresponds to approximately 2 to 5 grams of organoclay per 1,000 grams of paint mixture. Adjust as needed to achieve the desired consistency and thixotropy. It may also be used to modify the flow of pre-made tube paints, particularly when preparing impasto or textured applications. Incorporate organoclay directly into paint at 0.2% to 0.5% by weight, or as a pre-gel (5–10%). A polar Activator is not required for oil and alkyd paint.