Why Should You Hard Coat EPS Foam Props?

There are several reasons that you should hard coat EPS foam props. If they are being used or moved around frequently and are getting dinged, dropped, or even smashed in the process, they won’t last.

If these props are meant for outdoor use, they will wind up broken and damaged from weather conditions, including rain, sunlight, and extreme temperatures.

Even if your props aren’t meant for close human interaction, accidents can happen. If you plan to reuse your props or need them to last the entire production, they can’t be left unprotected.

A way around this has often been with fiberglass, but this material is expensive and time-intensive to use. An alternative is to harden your foam props and set pieces with a high-strength, protective EPS theming hard coat.

What Is EPS Foam?

EPS foam is often called styrofoam by many prop designers, but they are not the same. Styrofoam is a brand name for extruded polystyrene (XPS), whereas EPS is expanded polystyrene. While they use the same polystyrene base, the manufacturing process for each type is different.

Other foams can be used for props and set pieces, but EPS tends to be the easiest to work with, making it the most desirable. Compared to other materials like wood, metal, or concrete, it is also more affordable. It can be purchased in blocks or sheets at varying densities if it needs to be tougher for the desired project.

It is most recommended for props if they are to be moved around, which is frequently needed for movie, television, and theater productions. The lightweight nature of the foam makes it the obvious choice for creating large, oversized props. It allows productions to be more dynamic and efficient for smoother movement and transitions between scenes.

How Do You Make EPS Foam Props?

These days, most of what we see on our screens in terms of movie props and sets is computer generated. CGI took the industry by storm, but audiences are reverting to the desire for authenticity in media. Physical sets and props can bring back that authenticity. Making physical props is more affordable and easily customizable when you hard coat EPS foam. The prop making process goes like this:

• Designers and prop artists typically start by creating and mapping out a design using a computer program. They can be as creative as they want, which is helpful for designing realistic or imaginative props and set pieces.
• Following the creation of the prop design, foam is then carved using a number of methods, including CNCing, milling, hot wire cutting, etc. Shaping the foam is the most delicate part of the prop making process because of how fragile the foam can be, especially when adding extreme detail.
• Once you’ve gotten through the hard work of carving or machining the foam, a hard coat should be sprayed or brushed onto the surface. As a coating, the material adapts to the contours, curves, and edges of the foam without diminishing the details.
• After the hard coat has cured, the surface is sanded to a smooth finish to accept paint or a topcoat. Painting is the part of the prop making process that allows designers to enhance the aesthetic appeal of the prop to look real and life-like. It can even make the prop look like other materials, including wood, metal, and stone. Even with a lower budget, prop masters can make high-quality props with foam and hard coats.

Best Hard Coating Material for Foam Props

While there are several ways to harden EPS foam props, VFI has seen the most success with polyurethane hard coats. At 65-75 D Shore Hardness, these coatings create a strong, seamless shell over foam props. Hard coatings come with many benefits, including:

• Fast cure – Other hard coating materials for foam props can take much longer to apply and dry. For example, fiberglass is durable, but epoxy or polyester resin has to be applied by hand. The resin then dries slowly, so projects take time to finish. Urethane sprayable plastic coatings are applied quickly and cure after a few hours, which makes them better for quick project turnarounds.
• High durability – Foam can be pretty fragile on its own. When hard-coated, it’s shielded to resist scratches, dents, chipping, etc., from movement or actors interacting with the prop. The coatings are also flexible enough to not crack from environmental extremes. They can be formulated with varying physical properties for long-term protection of the prop.
• Versatility – Urethane hard coats are versatile in many ways. They can be applied to large and small props made of various materials, including other foams like XPS and polyurethane. They can also be applied in different ways for different application needs. VFI specifically offers brushable, high pressure, and Qwik Spray hard coatings. These coatings can be used for indoor or outdoor projects as well, depending on if they have fire testing.
• Fire testing – Because many props and set pieces are used indoors, they may need to adhere to strict fire safety regulations. VFI’s urethane hard coats can pass ASTM E84 Class A fire testing. Class A is the highest classification these coatings can achieve under this test. In the event of an accident, the coating will not add to flame spread and can minimize damage.

What Kind of EPS Foam Props Can You Hard Coat?

Handheld props are often the most common props made of EPS foam. Since they are small and can be held, a brushable hard coat is typically the preferred coating to protect them. The only issue is that you must work in an environment with low humidity when applying brushable urethane to prevent bubbling.

If you are only making handheld props, the cost of a high pressure spray rig may be out of the question. Otherwise, if you’re making small props frequently, you might want a hard coat that can be sprayed through a cartridge-based gun.

On the other hand, the best way to hard coat oversized props and large set pieces is with a high pressure spray coating. If your set needs a rocky landscape, sculptures, or furniture, a brushable hard coat will not be able to accommodate the size of the piece. It’s also more cost-effective for a company that creates a lot of large foam props to get a high pressure spray system or a Qwik Spray Gun.

Hard coats can even adhere large foam pieces together, so brushable and spray applied coatings can be used in conjunction. Even if you are mostly spraying, it can be a good idea to keep some brushable hard coat around in case you need to make repairs.

Other props that designers may not realize could also be made of hard coated foam are architectural accents and custom signs. Foam makes an excellent alternative to stone and wood when making these features. We’ve even seen success with foam columns, trim, molding, shutters, corbels, signs, and more on the outside of actual homes. If these materials are used for decorative architecture, you know they’ll be able to withstand various conditions on movie and theater sets.

Contact VFI if you’d like to learn more about our hard coatings or need help determining the best one for you.