Calcite oil absorption is a critical technical parameter that determines how calcium carbonate behaves in paint and plastics formulations. Oil absorption is the amount of oil (usually linseed oil) needed to wet 100 grams of powder into a paste, expressed as g/100g. Low oil absorption means higher loading and lower cost with the same resin, so it is a key advantage in calcium carbonate (CaCO₃) formulations.
This guide covers what calcite oil absorption is, how it is measured, which factors affect it, why it matters in paint and plastics, and the effect of low oil absorption on cost. It is written for the R&D, quality-control and procurement teams of paint and plastics manufacturers.
Quick answer: Calcite oil absorption is the amount of oil needed to saturate 100 g of powder (g/100g), measured with linseed oil per ISO 787-5. Ground calcite (GCC) has low oil absorption (~13-21 g/100g); precipitated calcite (PCC) and very fine powders are higher. Surface coating (stearic acid) lowers oil absorption. Low oil absorption enables higher loading and lower resin demand.
What Is Calcite Oil Absorption?
Oil absorption is a measure of the amount of liquid needed to wet the surface and inter-particle voids of a filler powder. In the standard method (ISO 787-5), linseed oil is added drop by drop and the powder is worked with a spatula until it forms a single liquid paste; the oil used is expressed per 100 grams. For calcite’s general properties, see our what is calcite guide.
If oil absorption is low, the powder needs little liquid to wet its surface; if high, it needs a lot. In a paint or plastics formulation the “liquid” is resin/binder or plasticizer. Oil absorption is therefore directly related to resin demand and loading level.
Calcite Oil Absorption Values
| Product type | Typical oil absorption (g/100g) | Comment |
|---|---|---|
| Coarse ground calcite (GCC) | ~13 – 18 | Very low; high loading |
| Fine micronized calcite (GCC) | ~18 – 25 | Increases with fineness |
| Coated calcite | Lower than uncoated | Stearic acid saturates the surface |
| Precipitated calcite (PCC) | ~25 – 60 | High surface area and fluffiness |
General rule: the finer the particle (the higher the surface area), the higher the oil absorption. For this behavioural difference between ground (heavy) and precipitated (light) calcite, see our heavy vs light calcium carbonate guide.
What Affects Oil Absorption?
- Particle size and fineness: finer powder = higher surface area = higher oil absorption. See our micron size guide.
- Surface area (BET): porous, high-surface-area particles hold more liquid.
- Particle shape and packing: fluffy, irregularly packed powders (such as PCC) give higher values.
- Surface coating: stearic-acid coating makes the surface hydrophobic and lowers oil absorption. See our natural vs coated calcite guide.
Why Does It Matter in Paint and Plastics?
Calcite oil absorption directly influences formulation decisions in two major application areas:
- In paint: oil absorption determines binder demand and the pigment volume concentration (PVC/CPVC) balance. Low-oil-absorption calcite allows more filler and TiO₂ saving. For the relationship, see our calcium carbonate in paint guide.
- In plastics (especially PVC): oil absorption affects plasticizer demand. A high value requires more plasticizer and raises cost. For the PVC side, see our PVC pipe and profile guide.
At the same time, high oil absorption is not always bad: in sealants, adhesives and matt coatings it can be desirable for body (thixotropy) and sag resistance. The decision depends on the application’s needs.
Low Oil Absorption and Cost
Low-oil-absorption calcite allows a higher loading level with the same amount of resin/binder. This is a direct cost advantage: economical filler replaces expensive binder and lowers formulation cost. This property gives calcite an advantage over some other filler minerals (such as talc or kaolin); for a comparison, see our calcite vs talc guide.
Oil absorption should be evaluated together with other quality parameters such as brightness and particle size. For brightness, see our calcite brightness guide.
How Is Oil Absorption Measured?
The most common method is the ISO 787-5 spatula (rub-out) method: linseed oil is added to the powder in a controlled way and worked until it forms a single, non-crumbling paste. The mass of oil used is expressed per 100 grams. The Gardner-Coleman method is also used. At Aydın Madencilik, oil absorption is one of the parameters measured in the quality-control laboratory; for our processes, see our laboratory page.
Oil Absorption and the PVC/CPVC Balance (in Paint)
In paint formulation, oil absorption directly governs binder demand and the pigment volume concentration balance. Here PVC does not mean polyvinyl chloride plastic; it stands for pigment volume concentration — the volume ratio of pigment plus filler to the total solids in the dry film. The critical pigment volume concentration (CPVC) is the point at which the binder can just fully wet every particle surface and fill the voids between particles. Above this limit the film retains unwetted air voids, and gloss, hiding power and mechanical strength all deteriorate together.
Low-oil-absorption calcite reaches the CPVC limit later for the same amount of binder, so more filler can be loaded below CPVC without losing film properties:
- Higher filler loading: staying below CPVC lowers resin demand and reduces cost.
- Preserved film integrity: the binder fully wets the particle surfaces, keeping gloss and hiding power stable.
- TiO₂ saving: more calcite as an extender can replace part of the expensive titanium dioxide; for the relationship, see our calcium carbonate in paint guide.
Lowering Oil Absorption with Surface Coating
One of the most effective ways to lower oil absorption is to coat the calcite particle surface with a fatty acid such as stearic acid. The coating turns the hydrophilic calcite surface hydrophobic and wraps each particle in a thin organic layer. This layer reduces the amount of liquid held at the particle surface, so less oil, resin or plasticizer is needed to reach the same paste consistency. The result is lower binder demand in both paint and plastic systems such as PVC. For the coating types, see our natural vs coated calcite guide.
The practical benefits of coating are:
- Higher loading: the reduced liquid demand allows more calcite to be loaded into the polymer.
- Better dispersion: the hydrophobic surface helps particles disperse without agglomeration in polymer and solvent-based systems.
- Lower plasticizer demand: in PVC applications plasticizer consumption falls and cost drops; see our PVC pipe and profile guide.
Aydın Madencilik Calcite Product Range
Aydın Madencilik sources all of its raw material from its own licensed reserves and produces low-oil-absorption, high-purity ground calcite. Our natural and coated options are optimised for different loading and rheology needs.
| Product group | Range | Oil absorption tendency |
|---|---|---|
| Micronized calcite (AY 103 – AY 1000) | 3 – 100 µm | Low (rises with fineness) |
| Coated calcite (K series) | 3 – 20 µm | Lower than uncoated |
| Calcite stone | Granular / coarse | Very low |
All micronized grades have CaCO₃ above 98%, Fe₂O₃ below 0.1% and ISO brightness of 93+. Explore the full range on our micronized calcium carbonate page, or visit our laboratory page for the oil absorption values of our products.
Frequently Asked Questions (FAQ)
What is calcite oil absorption?
Calcite oil absorption is the amount of oil (linseed oil) needed to wet 100 grams of calcite powder into a paste, expressed as g/100g. The lower the value, the less resin/binder the powder needs — meaning higher loading and lower cost.
How is calcite oil absorption measured?
The most common method is the ISO 787-5 spatula (rub-out) method: linseed oil is added to the powder in a controlled way and worked until a single paste forms; the oil used is expressed per 100 grams. The Gardner-Coleman method can also be used.
What affects oil absorption?
The biggest factor is particle fineness and surface area: finer powder gives higher oil absorption. Particle shape, porosity and surface coating also matter. Stearic-acid coating lowers oil absorption.
Why is low oil absorption an advantage?
Low oil absorption allows more filler to be used with the same resin. This lowers formulation cost in paint and plastics and contributes to titanium dioxide saving in paint.
Which has lower oil absorption, GCC or PCC?
Ground calcite (GCC) has markedly lower oil absorption than precipitated calcite (PCC). GCC is in the ~13-21 g/100g range, while high-surface-area PCC can reach 25-60 g/100g.
Is high oil absorption always bad?
No. In sealants, adhesives and matt coatings, high oil absorption can be desirable because it provides body (thixotropy) and sag resistance. The decision depends on the application’s needs.
What is the oil absorption of Aydın Madencilik calcite?
In Aydın Madencilik ground (GCC) calcite products, oil absorption is low and varies in a controlled way with micron fineness; it is even lower in the coated options. Our team can help you set the right value for your application; use our get a quote or contact page.
What is the unit of oil absorption?
Oil absorption is expressed as the amount of oil needed to saturate 100 grams of filler, so its unit is g oil / 100 g filler (g/100g for short). Some sources report the same value in millilitres per 100 g of powder. The lower the value, the less liquid — resin or plasticizer — the powder requires.
What is DOP absorption?
DOP absorption is an absorption test that uses the plasticizer dioctyl phthalate (DOP) instead of linseed oil. It is meaningful for plasticizer-bound applications such as PVC, because it better reflects how much plasticizer the filler will consume in the real system. The principle is the same as oil absorption: low DOP absorption means lower plasticizer demand and a more economical formulation.
What does high oil absorption indicate?
High oil absorption usually indicates that the powder has fine particles, a high surface area and a porous or fluffy structure. Such powders need more liquid to wet their surface, which means higher binder demand in the formulation. Very fine micronized grades and precipitated calcite (PCC) therefore give higher values.
How does BET surface area affect oil absorption?
BET surface area is the total specific surface area of a powder measured by gas adsorption (m²/g). As surface area rises, so does the area that must be wetted, so a higher BET surface area leads directly to higher oil absorption. Fine grinding and porosity raise the BET value, while coarse, blocky GCC particles give low surface area and low oil absorption.
How much does coating lower oil absorption?
Stearic-acid coating lowers oil absorption noticeably compared with the same uncoated powder, but the exact reduction depends on the product’s fineness, surface area and coating level. For that reason no single fixed value can be quoted. The actual oil absorption of the coated grade suited to your application is stated in our technical data sheets and laboratory measurements.
Related Guides
More technical content on calcite oil absorption and filler performance:
- What Is Calcite? — complete guide to calcium carbonate
- Micron Size — how fineness and surface area matter
- Natural vs Coated Calcite — the effect of stearic-acid coating
- Heavy vs Light Calcium Carbonate — GCC and PCC behaviour
- Calcium Carbonate in Paint — extender pigment and TiO₂ saving
- Calcite Brightness — ISO brightness and colour quality
- Calcium Carbonate in PVC Pipes — plastics and plasticizer demand
Choose Calcite with the Right Oil Absorption for Your Application
Calcite oil absorption is a parameter to be evaluated through loading target, resin cost and rheology needs. Calcite with the right value improves both formulation cost and end-product performance.
The Aydın Madencilik technical team will help you select the right-oil-absorption calcite grade and micron range for your application: Request a sample | Explore the product range
