How to Paint Expanded Polystyrene

Expanded polystyrene is one of several materials that must be painted with care. Due to its properties, using the wrong kind of paint can lead to disastrous results.

WHAT IS EXPANDED POLYSTYRENE? 

Expanded polystyrene, or EPS, is a plastic-based foam that is usually referred to as Styrofoam. Due to the abundance of air trapped among its particles, this material is used in applications in which thermal insulation, flotation and even shock absorption are desired properties. For this reason, it is normally used as protective packaging of electronics, for insulation in refrigeration units and for flotation in surfboards.

In addition, it is very useful in seasonal decorations, as it is inexpensive, light and may be sculpted into any shape. When painting EPS, it is extremely important to choose the right kind of paint. 

WHY CAN’T I PAINT STYROFOAM WITH ANY KIND OF PAINT? 

Because, being a plastic-based product that mostly consists of trapped air, it is highly sensitive to solvents. For this reason, applying solvent-based paints to EPS products will result in corrosion of the surface of the material and alteration of its original shape. Therefore, most paints that contain solvents, including most spray paints, are not suitable for this purpose. 

THE SOLUTION: MTN WATER BASED 

Taking into account these considerations, Montana Colors’ spray-paint offerings include an ideal product for this purpose. MTN Water Based paints contain no solvents and, when used correctly, will not compromise the stability of EPS. 

ANOTHER OPTION: WATER BASED PAINT 

In addition to the MTN Water Based 300 and 100 spray paints, Montana Colors also makes a water-based paint in traditional format: MTN Water Based paint. This paint may be applied to EPS products with a brush or any other method and will not deform the material. 

HOW TO SPRAY PAINT EPS SURFACES 

In order to correctly use MTN Water Based spray paints, we must follow the typical instructions for these kinds of products: 

- Shake the aerosol vigorously for one minute after you start to hear the ball bearing rattle inside the can.

- Release the solvent inside the cannula by spraying a test surface. This will help you to gauge the flow of paint and to use the spray correctly.

- Apply from a distance of 8 to 10 inches.

- Hold the aerosol upside down and spray until no more paint is released. This helps prevent blockage of the diffuser, so that you won’t have to buy a new one the next time you want to use the spray paint.

- Each coat of paint must dry for 15 minutes before applying another, and the paint will be touch-dry after 30 minutes. 

WATER-BASED PAINT IS USEFUL AS AN EPS PRIMER 

Water-based paint applied to Styrofoam surfaces can be used to protect the material from the corrosive effects of solvent-based paint. In this way, water-based paint can be used as a primer for the subsequent application of other kinds of paint, regardless of their composition. 

This is an important advantage when, for example, water-based spray paints are not sold in the color you wish to paint the EPS. 

WATER-BASED VARNISH 

As stated, a layer of water-based paint will protect EPS surfaces from the potentially corrosive effect of applying another coat of paint. However, when varnishing, if we want to be absolutely sure there will be no corrosive reaction to the material, the best solution is the MTN PRO range of water-based varnishes. Indoor and outdoor protective varnishes. Choosing one or the other will depend on whether the varnished item will be used indoors or outdoors.

In this brief article, we've explained all you’ll need to know about painting expanded polystyrene. Nonetheless, you can always ask for information at [email protected] or wherever MTN products are sold.