Advantages of Using a Form Coating Epoxy

There are several advantages of using a form coating epoxy over expensive precast forms, surfaces, and molds. Forms are essential for casting concrete, as they hold and shape the wet material as it cures. However, if you want to repeatedly use these forms without damaging them, you’ll need to apply a form coating. This protective coating will contribute to the long-lasting success of the casting surface.

With an understanding of how to use a form coating epoxy to protect surfaces from abrasive damage, you can create an abundance of quality precast products from a single surface or form. Here are several advantages:

• Extended protection – Using an appropriate form coating epoxy will ensure that the surface can withstand the weight and abrasive characteristics of the casting material during the pouring and demolding process. While rigid, it is also formulated with some flexibility so it will limit cracking without fabric or polyester reinforcement. The coating minimizes abrasion, impact damage, wear, and chemical or moisture exposure to enhance the quality, durability, and life of the surface.
• Reusability – Some materials are more durable than others. After repeated use, the casting surface can deteriorate. When a form coating epoxy is applied, it makes the surface durable, lengthening the life of the form so it can be used over and over without damaging the underlying surface. The coating is also repairable. It can be sanded and reapplied for continuous protection.
• Smooth finish & improved quality – Applying a form coating can improve the overall quality of the casting. It creates a self-leveled surface that is flat enough to distribute the casting material evenly. The coated surface also ensures that the final precast product will have clean edges and smooth surfaces. Without the coating, there may be a rough, uneven texture on the surface of the cast piece. So, you’re not only lengthening the life of your form, but you’re also improving the aesthetics of the finished product.
• Easier casting removal – While a release agent is recommended before casting, the surface will be smooth and non-porous when the coating is applied. The casting mixture will not seep into the surface beneath the coating, which allows it to detach from the surface more easily. The easier release means less effort is required to remove the casting. The coating also prevents waste since the casting will come out intact, and the surface is undamaged for reuse.
• Versatility – A form coating epoxy is extremely versatile as it can be applied to a variety of surfaces using a roller. It bonds well to metal, wood, and foam. It should be able to contour to corners and edges no matter the shape or size of the form.
• Reduced maintenance – Because the epoxy is a smooth, non-porous material, it is easier to clean surfaces between castings. There’s no worry about debris, dust, or moisture slipping beneath and contaminating the form, which means faster turnaround times.

Types of Forms That Can Benefit

When deciding the type of material to use for your form or mold, there are a few things you should take into consideration. The surface material should be non-porous, non-reactive with the casting material, level, and rigid. A desirable form material would also be capable of accepting a coating that could reduce the adhesion between the surface and the casting material. Some common molding materials that could benefit from using a form coating include:

Metal

These forms are typically made of steel due to their reusability. They’re rigid, durable, and provide a smooth surface for casting. Simple, preformed metal surfaces make practical molds for casting. They will be more expensive than other materials due to their extended durability.

However, not covering the molding surface with a form coating epoxy can cause the metal to deteriorate faster than anticipated. Casting abrasive materials, like concrete, that contain alkalis directly onto a metal surface can cause corrosion. When the coating is used, it will prevent direct contact between the surface and the casting material. This barrier will protect the surface from developing imperfections that will affect the final cast quality.

Another reason a form coat epoxy should be applied to metal is so the casting material won’t bond to the surface and cause damage in the removal process. Because these forms are so expensive, it’s important to protect them for long-term use.

Wood/Sheet Goods

Wood and sheet good forms are the most basic and can be made of timber, plywood, particle board, or MDF. They will generally be simple, rectangular, and flat. Although these materials are easy to work with and cost-effective, they have a relatively short lifespan and won’t offer the same reusability as other materials.

Casting materials will stick more easily to an uncoated surface, which makes cured pieces difficult to remove. This adhesion can damage the surface, preventing the mold from being reused, and it will need to be repaired after each use. When a form coating epoxy is applied to a porous surface, it reduces the chance of adhesion or moisture absorption and increases the reusability of the form. If the surface absorbed some of the moisture from the cast material, it could cause it to swell and warp, leading to a poor cast. The absorption could also promote rot as the wood would absorb moisture and promote fungal growth.

The coating also, if necessary, can prevent the casting from copying the natural grain texture from the wood. When applied to the wood surface, it covers the texture and any imperfections, so the casting surface is smooth and non-textured.

EPS Foam

Foam forms are typically chosen for the ability to use a machine to create a specific shape without the additional labor of making them by hand. A machine-made foam part is used when a low-weight and highly precise mold is necessary. Since the foam is fairly delicate, it’s usually made for a single use or limited use based on the shape.

Solid blocks of foam can be carved to achieve a desired shape for casting. Foam pieces can also be glued together to create walls to pour casting materials into. However, the only way EPS is capable of being a casting surface is if a durable form coating is applied. The coating will make the foam more rigid and capable of withstanding abrasion and wear. This option also tends to have a lower cost than other materials because foam is inexpensive.

How to Prevent Form Failure from Occurring

Before pouring your casting material, prepare the surface to avoid issues. Certain factors can cause the form to fail. There are several ways to prevent that failure from occurring:

• Ensure adequate strength of the form – A strong form is essential to withstand the weight and abrasion of various casting materials, like concrete. Even the toughest surface will be prone to failure if you overfill the mold. That’s why a form coating is applied over the surface. It is rigid and takes on some stress during casting, so the surface is stable and reusable. Make sure the weight is distributed evenly, which can be done by vibrating the form. An adequate amount of coating will need to be applied based on the form material and thickness of the cast.
• Be cautious when using old materials – A form coating epoxy will wear over time due to the abrasion and wear caused by the casting material. The great thing about using one is that it can be reapplied. Look for signs of deterioration in the coating after each cast. If it’s time for a new application, sand the original coating and apply a new coat. It takes much less time to restore the coating than it would to replace an entire form.
• Don’t neglect maintenance – Conducting regular maintenance will prevent future failure due to deterioration of the coating. The coated surface should be cleaned after each casting is removed to maintain its integrity. Maintenance includes removing any casting residue before it is stored for future use. Ideally, you’ll want to store your forms indoors in a controlled environment.
• Take your time and be patient – Allow the concrete to cure properly before it is removed to prevent failure of the form. If you try to speed up the demolding process, you may end up with subpar castings or a damaged form.

If you want to protect your precast forms, contact VFI for information about our VFI-4385 82 D Form Coating Epoxy. We also have a polyurethane alternative: VFI-2538 70 D EPS Form Hard Coat.