Lesson 20. Types of Fillers

In this lesson we will examine the main materials used for producing fillers and their areas of application, as well as analyze how fillers interact with operational and aesthetic factors.

Main Types of Fillers

1. Marble

Marble is one of the most universal and widely used types of filler in decorative plasters and paints. Its popularity is explained not only by aesthetic qualities but also by an excellent combination of physical properties. Marble is obtained by crushing and finely grinding natural marble — a rock. This natural origin makes marble environmentally friendly and safe for use both indoors and outdoors.

One of the most important qualities of marble is its color. In pure form it has a bright white shade, making it an ideal base for tinting. In addition, due to its relative softness, marble is easy to grind and polish. This is especially important when creating smooth and glossy surfaces such as Venetian plaster.

Marble chips come in many different sizes — from powder‑like marble flour used in thin‑layer and glossy coatings, to coarse fractions intended for textured facade and interior plasters. All this makes marble the most popular filler in the world of decorative materials.

2. Quartz

Quartz is the “armor” in the world of fillers, used where maximum strength and resistance to aggressive influences are required. The basis for production is natural quartz — one of the most common minerals on the planet. It is extracted from quartz veins or sandstones, then purified and ground to the required fraction. The result is fillers of different sizes: from fine quartz dust to granular sand and even chips.

The main quality of quartz is its high hardness. On the Mohs scale it has a value of 7, which makes it much harder than marble, which has a value of 3. Thanks to this hardness, quartz provides excellent resistance to abrasion, scratches, and mechanical damage. In addition, quartz is chemically inert: it does not react with acids or alkalis, and is resistant to ultraviolet radiation and weathering. This makes it an ideal component for outdoor applications and use in harsh conditions.

Another important property of quartz is the transparency or semi‑transparency of its crystals. This means that even with a large amount of filler, it practically does not affect the color of the material, does not “clog” pigment tones, and does not make them cloudy. Therefore, quartz is often used in combination with colored and transparent binders, especially in decorative self‑leveling floors and glossy coatings.

Quartz filler is widely used in facade and base plasters where increased wear resistance is required. It is indispensable in adhesion primers such as “Betoncontact” — quartz sand creates the necessary surface roughness to which subsequent coatings adhere reliably.

Quartz is also the main filler in durable polymer floors, where high loads require materials with maximum abrasion resistance.

3. Cellulose and Wood Fibers

Cellulose and wood fibers are a special category of fillers. Unlike mineral components, they have an organic origin: they are made from processed fibers of wood, cotton, or other plant materials. These fibers undergo special treatment — grinding, cleaning, sometimes bleaching — and are added to decorative and construction materials in the form of dry, fluffy fractions or loose flakes.

The main distinction of these fillers is their lightness and volume. Even with low weight they can significantly increase the volume of the mass, creating a plastic, porous structure. This allows materials to be applied in thicker layers without excessive load on the substrate.

Importantly, cellulose fibers have a pronounced reinforcing effect: within the material structure they intertwine, forming something like an internal mesh. This structure helps distribute stress inside the layer and prevents the appearance of microcracks when thick layers dry.

From an aesthetic point of view, cellulose fillers create a very distinctive texture — soft, fibrous, slightly velvety. They are usually used in decorative plasters with pronounced texture.

4. Glass

Glass as a filler in decorative and construction materials is an interesting example of how the same material, depending on its form and size, can perform completely different functions. In the finishing industry, glass components are mainly used in two forms: glass beads and fiberglass. Their purpose, visual effect, and influence on material properties are fundamentally different.

Glass beads (microspheres) are microscopic round beads made of transparent or matte glass. Thanks to their shape, they can refract and reflect light, creating an effect of soft shimmering or visual depth in decorative coatings. They are often used in decorative paints, varnishes, and plasters to add a visual “sparkle” to the surface — especially under side lighting. Due to the high hardness of glass, they also improve the wear resistance of the finish. Such compositions are found not only indoors but also outdoors — for example, in road marking paints, where visibility under headlights is important.

Fiberglass (glass fiber) is a completely different material. It consists of very fine but very strong glass threads, usually several millimeters long. Unlike glass beads, fibers hardly affect the appearance of the material but significantly reinforce its structure. Inside plaster, these threads intertwine, forming a reinforcing mesh that prevents cracks.

Fiberglass is especially effective when applying materials in thick layers or on problematic substrates. Thanks to its strength and inertness, it is used in repair mixes, technical plasters, and any compositions where high crack resistance and durability are important. Cellulose and wood fibers also create a reinforcing mesh but are less resistant to moisture, so when producing moisture‑resistant or waterproof materials, manufacturers use fiberglass.

Thus, glass fillers are not only about aesthetics but also about functionality. The same base material, presented in different forms, can both decorate the surface and protect it from damage.

After examining the main types of fillers, we can now discuss the influence of this component on the properties of the material.

Influence on Operational Factors

Interaction with moisture

• Water resistance: Medium influence. Water resistance itself is determined by the binder. However, a very large amount of filler (especially cellulose) with a small amount of binder can make the coating more permeable to water.
• Moisture resistance: Indirect influence. Similar to water resistance.
• Vapor permeability: Low influence. In film‑forming systems vapor permeability is always low. In mineral systems it is high. The type of filler practically does not change the overall picture set by the binder.
• Wet abrasion resistance: High influence. Hard fillers (quartz, marble) significantly increase resistance to washing, as they create a strong framework. Soft fillers (cellulose) can reduce it.
• Resistance to biological damage: Low influence. Determined by the binder or special additives. Most fillers are chemically inert and do not affect this parameter.

Interaction with mechanical impact

• Abrasion and scratch resistance: Very high influence. This is one of the main technical functions of filler. Quartz and other hard minerals make the coating significantly more wear‑resistant.
• Impact resistance: High influence. Coarse filler excellently distributes and absorbs impact energy, protecting the surface. c) Elasticity and crack resistance: Medium influence. Fibrous fillers (fiberglass, cellulose) act as a micro‑reinforcing mesh, increasing crack resistance and elasticity of the whole system.

Other specific operational factors

• UV resistance: High influence. Mineral fillers (marble, quartz) are absolutely inert to UV radiation and increase the overall lightfastness of the coating, protecting the binder from part of the radiation.
• Heat resistance: High influence. Mineral fillers (quartz, marble) significantly increase the heat resistance of the material, since they do not melt and do not burn.
• Frost resistance: Medium influence. Strong, non‑porous fillers (quartz, granite) improve the frost resistance of the coating.
• Environmental safety in use: High influence. All mineral and most organic fillers are absolutely natural and environmentally friendly components.

Influence on Aesthetic Factors

• Color (tinting possibilities): High influence. The color of the filler itself affects the final shade. Bright white marble allows pure and light colors. Grayish or yellowish sand will “contaminate” the shade. Transparent quartz practically does not affect color. In some pebble decorative plasters, the color of the filler creates the main decorative effect, and in such materials the grain color plays a key role.
• Texture and relief: Defining influence. This is the main aesthetic function of filler. The size, shape, and quantity of particles 100% determine whether the coating will be smooth, rough, or textured.
• Gloss level: Defining influence. Gloss is possible only with microfillers (dust, flour). Any larger filler creates roughness that scatters light and makes the surface matte.
• Optical effects: High influence. Special fillers create unique effects: glass beads — shimmering and light reflection. Metallic or pearlescent particles in the filler composition can create a soft light play.

We have now fully examined the “skeleton” (binder) and the “body” (filler) of any decorative material. You now know how the binder determines basic properties (strength, elasticity, water resistance), while the filler defines texture, volume, and application technique. Next comes the section on pigment. Pigments are responsible for the visual perception of the material, its mood, and character. This is the third fundamental component that shapes the external appearance of the coating.