Cork Granules – Grain Sizes, Properties & Applications

A versatile natural material for filling, designing, mixing and insulating

Cork granules consist of small cork particles and combine the characteristic properties of cork with the special possibilities offered by a loose-fill material.

Depending on the grain size, quality and intended application, cork granules can be used for model making, terrariums, decoration, gardening projects, as a filling and loose-fill material, as well as for certain insulation applications.

At korkie, we currently stock natural cork granules with a grain size of 2–4 mm. This grain size is particularly suitable for a wide range of creative and decorative applications as well as for use as a versatile loose-fill material.

For larger insulation projects, other grain sizes and significantly larger quantities may be required depending on the construction. These can be requested from us individually.

In this guide, we explain what cork granules are, why grain size matters and what you should consider when choosing the right material for your project.

👉 Discover cork granules 2–4 mm

👉 Which type of cork is right for your project?

What are cork granules?

Cork granules are not a separate type of cork, but rather a loose product form made from crushed cork.

The cork is broken down into individual particles that can be sorted according to their size or grain size. Different particle sizes and qualities are possible depending on the manufacturing process, raw material and intended use.

Unlike agglomerated cork, the granules are not bonded together with a binder to form a solid material. They initially remain loose and can therefore be:

✔ poured
✔ spread
✔ used as filling
✔ measured and dosed
✔ combined with other suitable materials
✔ or further processed as a raw material

Cork granules also play an important role in the production of various cork materials. For example, cork granules can be combined with a binder to produce agglomerated cork.

👉 Agglomerated Cork – Production, Properties & Applications

💡 Good to know

Cork granules, agglomerated cork and expanded cork are not the same thing.

Cork granules initially refer to the loose cork particles.

In agglomerated cork, cork granules are bonded together with a binder to form a solid material.

Expanded cork, on the other hand, is produced using a thermal process in which cork's own components play an important role in bonding the material.

👉 Natural Cork, Agglomerated Cork & Expanded Cork – What’s the Difference?

What role does grain size play in cork granules?

The grain size describes the size of the individual cork particles. Among other things, it influences the structure of the granules, their loose-fill behaviour and the possibilities for further processing.

The appropriate grain size therefore always depends on the intended application.

Finer grain sizes create a finer, more uniform structure and can be suitable for smaller model-making, design or mixing applications, for example.

Coarser grain sizes have a more clearly visible structure and, depending on the quality and project, can be used for filling, loose-fill or other technical applications.

The important point is:

Finer does not automatically mean better – and neither does coarser.

What matters is the particle size and material quality required for the individual project.

💡 Good to know

Cork granules should not be selected solely on the basis of their grain size.

The raw material, quality, required quantity and intended application also play an important role. Particularly for technical or insulation applications, the entire construction should therefore be taken into account.

Our 2–4 mm cork granules

At korkie, we stock natural cork granules with a grain size of 2–4 mm.

The medium grain size makes them a versatile material for numerous creative, decorative and practical applications.

Our 2–4 mm cork granules are particularly suitable for applications such as:

✔ model making and landscape modelling
✔ terrariums
✔ decoration and surface design
✔ planters
✔ gardening projects
✔ filling and loose-fill applications
✔ creative DIY projects

The granules are available in various quantities, making them suitable for both smaller projects and applications requiring larger amounts of material.

👉 Discover cork granules 2–4 mm

What can cork granules be used for?

Thanks to their loose form, cork granules can be used in many different ways. The suitability for a particular application depends especially on the grain size, quality and required quantity.

Model making and creative design

Cork granules can be used as scatter material, structural material or a design element, for example.

Their natural, irregular structure can be used to create individual surfaces, landscapes and creative projects.

Terrariums and decoration

Our natural 2–4 mm cork granules can also be used as bedding or decorative material in terrariums, as well as for other decorative applications.

Planters, bowls and other decorative objects can also be designed using this lightweight natural material.

Gardens and planters

Depending on the application, cork granules can be used to loosen heavy soils or as a lightweight structural material in gardening and planting projects.

Because cork is very lightweight, granules can also be useful where additional mineral materials would add unnecessary weight.

Filling and loose-fill applications

The loose form of the granules makes it possible to fill cavities or suitable constructions.

The required grain size and quantity depend on the dimensions, construction and desired function.

Raw material for other cork products

Cork granules are also an important raw material for further cork processing.

For example:

Cork granules + binder → agglomerated cork

and through appropriate thermal processing:

Cork granules → expanded cork

This means that cork granules are not only a material that can be used on their own, but also an important raw material for other cork products.

👉 Agglomerated Cork – Production, Properties & Applications

👉 Expanded Cork – Production, Properties & Applications

How much cork granulate do I need?

When working with loose cork granules, volume is often just as important as weight when planning a project.

As a guideline for our 2–4 mm cork granules:

25 g corresponds to approximately 300 ml or 0.3 litres.

This is approximately:

25 g ≈ 0.3 l ≈ 0.0003 m³

The actual amount of granules required depends on the area or volume to be filled and on how the granules are placed or compacted.

Simple volume calculation

For a rectangular cavity, you can first calculate the required volume:

Length × width × height = volume

Example:

An area measuring 100 × 50 cm is to be filled with cork granules to a height of 2 cm.

1.00 m × 0.50 m × 0.02 m = 0.01 m³

This corresponds to:

10 litres of volume

For precise quantity planning, please bear in mind that loose granules may settle differently depending on the fill, compaction and application.

🛠 Workshop Tip from korkie

For larger projects, first calculate the required volume rather than just the weight.

With a very lightweight material such as cork granules, the amount required can often be estimated more accurately based on the space that needs to be filled.

For larger quantities or special applications, simply send us the dimensions, desired fill height and intended use. We will be happy to help you determine a suitable quantity and grain size.

Cork granules as insulation material

Due to its characteristic cellular structure, cork has thermal insulation properties and interesting acoustic characteristics. Depending on their quality and the overall construction, cork granules can therefore also be used for certain loose-fill and insulation applications.

However, it is important to remember:

Not every grain size and every type of cork granulate is automatically suitable for every insulation construction.

The appropriate material depends, among other things, on:

✔ grain size
✔ bulk density and product quality
✔ required fill depth
✔ construction and building component structure
✔ desired thermal or acoustic function
✔ technical requirements of the project

Our stocked 2–4 mm natural cork granules are a versatile material for numerous applications. For larger or technical insulation projects, however, other grain sizes, qualities and significantly larger quantities may be required.

These can be requested from us according to the individual project.

👉 Cork Insulation – Thermal Insulation, Sound & Applications (coming soon)

💡 Good to know

For insulation projects, cork granules should not be selected solely according to particle size.

The complete construction is always decisive. For building applications or technically specified uses, the required technical values and requirements of the respective construction must also be taken into account.

Cork granules, agglomerated cork or expanded cork – what is the difference?

These materials are closely related, but differ in the way they are processed.

Cork granules: consist of loose cork particles of different grain sizes and can be used directly as loose-fill, filling, design or raw material.

Agglomerated cork: cork granules are combined with a binder to create a solid material.

Expanded cork: cork granules are thermally treated and expanded. In traditional expanded cork, no additional synthetic binder is required to bond the cork granules together.

👉 Agglomerated Cork – Production, Properties & Applications

👉 Expanded Cork – Production, Properties & Applications

Common mistakes when choosing cork granules

Cork granules are extremely versatile. However, the appropriate quality should always be selected according to the specific application.

Typical mistakes include:

❌ Choosing the grain size based solely on appearance
Particle size affects the structure and loose-fill behaviour. What matters is which properties are required for the project.

❌ Assuming that finer or coarser automatically means better
A particular grain size is not inherently higher quality. Different applications may require different particle sizes.

❌ Calculating larger projects by weight only
With loose granules, the required volume is often a better basis for quantity planning.

❌ Using every type of cork granulate as insulation material
For insulation projects, grain size, quality, bulk density, fill depth and the entire construction must be considered.

❌ Permanently bonding granules without testing first
On visible surfaces, an adhesive can change the structure and appearance. A small test area helps you assess the result beforehand.

🛠 Workshop Tip from korkie

When choosing cork granules, always start with the question:

What does the granulate need to do in my project?

Different criteria may be important for model making, decoration or planters than for filling, loose-fill or insulation applications.

For larger or technical projects, information about the intended use, area or volume and desired fill depth helps us assess the required quantity and a suitable grain size.

🌿 Conclusion – the application determines the grain size and quantity

Cork granules are a loose product form made from crushed cork and can be used for numerous creative, decorative, technical, filling and loose-fill applications.

Our readily available 2–4 mm natural cork granules are suitable for model making, terrariums, decoration, planters and various DIY projects, for example.

At the same time, cork granules are an important raw material for other cork products. Depending on the processing method, they can be used to produce agglomerated cork and expanded cork.

For larger insulation projects, other grain sizes, qualities and quantities may be required. These can be requested from us individually.

The key principle when choosing cork granules is:

There is no universally “best” grain size – the requirements of the individual project determine the right choice.

👉 Discover cork granules 2–4 mm

Frequently Asked Questions about Cork Granules

What are cork granules?
Cork granules consist of crushed cork. The individual particles can be sorted according to their size or grain size. The granules remain loose and can either be used directly or further processed into other cork materials.

What grain size are the cork granules available from korkie?
Our currently stocked natural cork granules have a grain size of 2–4 mm.

For larger or special projects, other grain sizes and quantities can also be requested depending on the application.

What are 2–4 mm cork granules suitable for?
Our 2–4 mm granules are suitable for model making, terrariums, decoration, planters, gardening projects and various filling, loose-fill and DIY applications, for example.

The suitability for a particular application depends on the individual project.

What volume do 25 g of cork granules have?
With our 2–4 mm cork granules, 25 g corresponds to approximately 300 ml or 0.3 litres.

For larger projects, we recommend calculating the required quantity based on the volume first.

How do I calculate the amount of cork granules I need?
For a rectangular cavity, the volume can be calculated using:

Length × width × height

All dimensions should be expressed in the same unit. For larger quantities, it should also be taken into account that loose granules may settle differently depending on how they are poured and compacted.

Can cork granules be used as insulation material?
Depending on their quality and the overall construction, cork granules can be suitable for certain loose-fill and insulation applications.

However, the appropriate grain size and quality depend on bulk density, fill depth, construction, desired function and technical requirements. Our stocked 2–4 mm granules should therefore not automatically be regarded as the ideal solution for every insulation project.

Other grain sizes and larger quantities can be requested for larger insulation projects.

👉 Cork Insulation – Thermal Insulation, Sound & Applications (coming soon)

Is cork granulate the same as agglomerated cork or expanded cork?
No. Cork granules initially consist of loose cork particles.

For agglomerated cork, cork granules are combined with a binder to form a solid material. Expanded cork, on the other hand, is produced through thermal treatment and expansion of the granules.

👉 Agglomerated Cork – Production, Properties & Applications

👉 Expanded Cork – Production, Properties & Applications

Are cork granules a natural material?
Our 2–4 mm cork granules are made from natural cork. Cork is a renewable raw material obtained from the bark of the cork oak.

👉 The Cork Oak – Origin, Cork Harvesting & Special Characteristics