Extruded Polystyrene foam or XPS Foam, commonly known as Styrofoam sheets, is often referred to as Blue Board when it is blue in color. This material is lightweight, strong, and long-lasting, making it perfect for creating terrains like hills and cliffs, constructing gaming boards, crafting various model elements such as bricks and buildings, and forming bases.

This material is a type of insulation material manufactured through an extrusion process where polystyrene crystals are melted and then forced through a die to create a closed-cell structure. This structure gives its characteristic smooth, dense surface and uniform cell size. Extruded polystyrene foam is particularly popular in model making and dioramas because it is easy to cut, shape, and paint, providing a stable and durable material for creating detailed miniature scenes and structures.

In model making, It is valued for its versatility and ease of use. It can be carved, sanded, and sculpted to create realistic terrain features such as hills, mountains, and rock formations. Additionally, its smooth surface allows for fine detailing, making it ideal for constructing buildings, ruins, and other architectural elements in dioramas.

Does XPS Foam Absorb Water?

XPS foam is highly resistant to water absorption due to its structure. This makes it an excellent choice for model making and dioramas that need to be painted, and also to be used in environments where humidity or accidental spills could be a concern. Unlike other sort of materials, where the cells are interconnected and can trap water, XPS foam cells are isolated from one another. This design prevents water from penetrating inside, ensuring that your models and dioramas remain intact and free from water damage.

However, while Styrofoam is water-resistant, it is not entirely waterproof, especially the open-cell version. that has a tiny amount of water absorption on the surface and therefore needs a craft sealer or decoupage medium to be applied. But overall, its water absorption rate is very low, usually less than 1% by volume. This resistance to moisture is a significant advantage in model making, where maintaining the integrity of the material is crucial.

XPS Foam | Extruded polystyrene foam

How to Cut XPS Foam Board?

Cutting XPS Styrofoam board for model making and dioramas can be done effectively with several tools, depending on the precision required and the thickness.

Here are some common methods:

Craft Utility Knife: A sharp craft knife is sufficient for thin pieces (up to 2 inches thick). Mark the cutting line with a straightedge, score the surface deeply with the craft knife, and then snap it along the scored line. This method is great for straight cuts and simple shapes.
Hot Wire Cutter: A hot wire cutter uses a heated wire to slice through smoothly. This method is ideal for achieving clean, precise cuts, especially for intricate shapes required in model making and dioramas. Hot wire cutters allow for detailed carving and shaping, which is essential for creating realistic terrain and architectural features.
Hobby Saw: A fine-toothed hobby hand saw can be used for thicker boards. These tools provide more control and can handle thicker materials better than a utility knife. They are useful for cutting larger pieces or making curved cuts.
ower Tools: Circular saws, table saws, or jigsaws fitted with fine-toothed blades can also cut it. These tools are suitable for larger projects or when multiple cuts are needed quickly. However, they might be overkill for smaller, detailed work typical in model making.

Regardless of the method, always ensure to wear protective gear such as safety glasses and a dust mask to avoid inhaling particles

How to Glue XPS Foam Together?

If you need to glue XPS foam for model making and dioramas require an adhesive that won't dissolve or damage the material.

For this reason, we recommend using adhesives specifically designed for polystyrene foam such as Tuft Glue. Solvent-free construction adhesives, foamboard adhesives, or polystyrene-safe spray adhesives are suitable choices. Avoid adhesives containing solvents like acetone or toluene, as they can dissolve it.

Here are some steps and tips for effectively gluing XPS foam:

Prepare the Surfaces: Ensure that the surfaces to be glued are clean and free from dust or debris. You can lightly sand the surfaces to enhance adhesion.
Apply the Adhesive: Apply a thin, even layer of adhesive to one of the surfaces of styrofoam sheets. For construction adhesives, use a caulk gun to dispense the adhesive in a zigzag pattern. For small, intricate areas in dioramas, a brush or a small applicator can be used.
Join the Pieces: Press the pieces together firmly. Ensure that the pieces are aligned correctly, as repositioning them after the adhesive sets can be challenging.
Clamp or Weight the Pieces: Depending on the adhesive used, you might need to clamp the pieces together or place a weight on top to ensure a strong bond. Follow the adhesive manufacturer's instructions for curing time.
Allow to Cure: Let the adhesive cure fully before handling the glued material. Curing times can vary, so refer to the adhesive's guidelines.

How to Paint XPS Foam?

Painting XPS foam for model making and dioramas requires some care to ensure the model paint adheres properly and doesn't damage the material. The material must be sealed and primed before starting. This is very important in general to paint any miniature, but much more necessary when we have to paint any kind of spume:

Here’s how to paint a Styrofoam:

Choose the Right Model Paint: Use water-based acrylic or latex paints, as they are safe. Avoid solvent-based paints, as they can dissolve it.
Prepare the Surface: Lightly sand the surface with fine-grit sandpaper to create a better surface for the paint to adhere to. Clean the surface with a damp cloth to remove dust.
Apply a Primer: Using a primer designed for plastics can help the paint adhere better and create a smoother finish. Apply a thin, even coat of primer and let it dry completely.
Paint it: Apply the paint using a paintbrush or a spray can for even coverage. Apply multiple thin coats rather than one thick coat to avoid drips and ensure an even finish. Allow each coat to dry before applying the next. This method is particularly useful for achieving detailed and realistic effects in dioramas.
Seal the Paint (Optional): For added durability, you can seal the painted surface with a clear acrylic sealer. This step is particularly useful if it will be exposed to handling or outdoor conditions.

Is XPS Foam Board Flammable?

Yes, it is flammable. It can ignite and burn when exposed to an open flame or high temperatures. To improve its safety in model making and dioramas, XPS foam boards are often treated with flame retardants. These additives help to slow the spread of flames and reduce their contribution to a fire.

When using it in model making, it is crucial to ensure it is not exposed to direct flames or high heat sources. Always work in a well-ventilated area and keep fire safety equipment, such as a fire extinguisher, nearby.

Is XPS Foam Toxic?

XPS foam is generally considered safe when used as intended, but there are some health and environmental concerns associated with its production, use, and disposal. During its manufacturing, it can release volatile organic compounds (VOCs) and other chemicals that may be harmful in high concentrations. this problem is controlled during production by taking appropriate measures to ensure the health of workers.

When cutting or sanding it for model making and dioramas, it's important to wear protective gear to avoid inhaling particles or dust. Proper ventilation is also recommended to reduce exposure to any potential VOCs released during these processes.

Heating Extruded Polystyrene foam can release harmful chemicals and fumes, posing several health risks. Toxic fumes such as styrene and benzene can cause skin, eye, and respiratory irritation, and chronic exposure increases the risk of serious health effects. Direct contact with heated materials can cause skin burns, and the fumes can irritate the eyes. To mitigate these risks, it is crucial to work in well-ventilated areas, use protective gear, and avoid using open flames or high-temperature heat sources.

Its disposal can be problematic, as it is not biodegradable and can persist in the environment for many years. Recycling options for this are limited, so it often ends up in landfills, where it can contribute to pollution.

What is the Difference Between EPS and XPS Foam?

XPS (Extruded Polystyrene ) and EPS (Expanded Polystyrene) are both types of materials, but they have different properties and manufacturing processes.

Extruded Polystyrene Foam is created through an extrusion process, which results in a closed-cell structure with uniform cell size and a smooth, dense surface. This structure gives its high compressive strength, making it ideal for applications requiring durability and support, such as building insulation, model making, and dioramas. It also has excellent moisture resistance due to its closed-cell nature, which prevents water absorption and maintains its insulating properties even in damp conditions. This material typically offers a higher R-value per inch of thickness compared to EPS, providing better thermal insulation performance.

Expanded Polystyrene (EPS) is produced by expanding polystyrene beads in a mold, leading to an open-cell structure with a more granular appearance. EPS is lighter and less dense looking like a block of little white balls, making it easier to handle and cut, which can be advantageous in certain applications like packaging and lightweight insulation. However, its open-cell structure makes it more susceptible to water absorption, which can reduce its insulating effectiveness over time if exposed to moisture. EPS is generally less expensive, offering a cost-effective solution for many uses. Despite being less durable, it is versatile and widely used in applications where weight and cost are more critical than compressive strength and moisture resistance.