EPS Foam or XPS Foam – which is best for diorama making

Trying to decide between XPS and EPS foam for your next diorama or scenery project? Read on to discover the key differences.

When creating dioramas, model railway landscapes and wargame scenery choosing the right foam material can make all the difference. The two most common types of foam used in modelling are EPS and XPS foam. Let’s take a closer look at these materials and their characteristics.

Before discussing foam, I should just clarify that polystyrene, which as explained below is used for foam, is also used for the manufacturer of hard plastics – of the sort used in Airfix and Tamiya models. This is completely different to the foam discussed here and beyond the scope of this article.

EPS Foam: what is it and its uses on dioramas?

EPS foam, or expanded polystyrene foam, is made by heating small polystyrene beads until they expand and fuse together, as explained by the British Plastics Federation here.

It’s cheaper than XPS foam and is often most commonly used as packaging material, to protect items in transit. (I have a shed full of the stuff I’ve collected from deliveries over the years and keep for future projects. Yes, I hoard packaging foam!!).

From our perspective, its low cost, lightweight and low density make it an ideal material with which to build terrain forms, profiles and shapes. Unfortunately, its low density makes it a poor choice for carving detail so to create the look and texture of rock outcrops, cliffs, river banks, and lake edging, you’ll need to add a surface layer of another material such as plaster, tin foil, or clay. And I’d never use it for man-made objects, stone or brick walls for example.

It’s also messy to work with. When cutting and carving it for terrain, I always end up surrounded by thousands of tiny polystyrene beads! Even in my tea in the first photo. You’ll definitely want a hoover nearby for cleanup.

XPS Foam: what is it and what can it be used for?

XPS foam, or extruded polystyrene foam of which Styrofoam by Dupont is the most well-known brand, is made by extruding polystyrene plastic through a die (as explained here by the University of New South Wales), resulting in a dense, rigid closed-cell foam that is most commonly used on building sites for wall, floor and pipe insulation.

Given its dense, closed-cell structure, XPS foam is ideal for carving and creating intricate shapes, such as stone walls and other architectural features on vignettes and dioramas. It’s typically more expensive than EPS foam, however, so I wouldn’t recommend it for any large terrain construction you might be considering.

For cutting (such as the stone bricks I was making above), carving and shaping, you’ll want either a hot wire cutter such as the Proxxon unit, a hot knife (but be wary of fumes – a mask is definitely recommended) or a good sharp blade, it can also be sanded using high grit sandpaper to a smooth finish.

Summary

Ultimately, the choice between EPS and XPS foam for dioramas comes down to your specific needs and preferences.

If you’re creating a diorama or scenery that features hills or uneven terrain that will be covered with other materials, such as scatter, EPS is ideal and my go-to material for such projects. If this is something you’re considering, read my guide to working with EPS foam.

By contrast, XPS foam is superior for fine surfaces and man-made structures such as brick or stone walls as props in D&D and wargaming, cliff faces and rock outcrops on model railways and structures in dioramas.

Have you used either EPS or XPS form for modelling? I’d love to hear what you made with it and how you got on, write a comment below and share your tips with others.

> A final, personal, note: I spend a huge amount of time testing, photographing, writing and researching techniques for these articles and pay for all the running costs of MRE out of my own pocket. If you found this article useful you can support me by making a donation on my fund-raising page. Thanks and happy modelling, Andy.