VFI®-6185 80 D Machinable Hard Coat

VFI’s hard coats come in a range of hardnesses from 50 D to 80 D. Since these materials are on the Shore D scale, they have a similar feel to a plastic hard hat.

When a coating lists 100% solids by weight or volume as a property, that means no solvents or other components leave during the curing process. The amount of material you put down on a surface is the amount of material that will remain when it cures.

All VFI hard coats come in an unpigmented neutral color, which is desirable for painting. When using the high pressure formula, clean your spray lines before application to ensure the color is not altered by previous material sprayed through the same lines.

For the coating to be used indoors and outdoors, it must be fire tested to meet strict fire safety regulations. VFI has several formulas that are great for indoor and outdoor applications: VFI-2626 65 D Brushable Hard Coat, VFI-6170 70 D Spray Hard Coat, VFI-6171 70 D Qwik Spray Hard Coat, and VFI-6185 80 D Machinable Hard Coat.

VFI-2626 65 D Brushable Hard Coat, VFI-6170 70 D Spray Hard Coat, VFI-6171 70 D Qwik Spray Hard Coat, and VFI-6185 80 D Machinable Hard Coat are fire-tested formulas that have passed the ASTM E84 Class A fire testing.

The best way to calculate the amount of material needed is to first determine how thick you want to apply the coating and how many square feet you need to cover.

As a standard, you can cover 100 square feet at 16 mils using 1 gallon of material.

For our cartridge-based formula, we made it easy to determine how many tubes of material you’ll require by offering a Qwik Spray coverage chart. Check it out on the VFI-6171 70 D Qwik Spray Hard Coat product page.

VFI hard coats are recommended for EPS since that is the type of foam designers and fabricators tend to use. It can also be applied to XPS (Styrofoam) or polyurethane foam. Please note that the foam must be aged for 30 days minimum to allow any gas to escape from the manufacturing process.

VFI requires a surface with a profile that allows for mechanical adhesion in order to apply our coatings. Ensure that the surface to be coated is clean, dry, and free of any contaminants that could affect adhesion. In some instances, a primer may be required.

When applying one of our hard coats over EPS, you typically will not need a primer. Always ensure the surface is clean and free of oils, dirt, debris, etc. that could affect adhesion. Some customers choose to use a two-part automotive primer or urethane bonding primer, but we recommend doing your own testing if you plan to try others.

The equipment used to apply these hard coats will depend on the product formula. VFI offers formulas with three different application methods: brush, Qwik Spray applicator, and high-pressure spray rigs.

– VFI-2519 75 D Brushable Hard Coat and VFI-2626 65 D Brushable Hard Coat are our brushable options and require chip brushes or trowels.

– VFI-6170 70 D Spray Hard Coat and VFI-6150 50 D Spray Hard Coat are our high-pressure formula and must be sprayed through a two-component, high-pressure spray rig. Several Graco and PMC air, hydraulic, or electric spray machines will accommodate the pressure and temperature required to spray the coating.

– VFI-6171 70 D Qwik Spray Hard Coat is offered in a cartridge format. This product requires a compatible applicator gun like VFI-7500 Qwik Spray Gun, which holds 750 mL dual cartridges. To run the Qwik Spray Gun, you will also need an air compressor that can supply clean, dry air at 100 psi and 10 cfm of constant pressure.

– VFI-6185 80 D Machinable Hard Coat is a trowelable options and is most often applied with a trowel or putty knife. For repairs, a brush can be used.

While we recommend applying hard coats when the environment temperature is around 72°F for consistent results, the high pressure coating can be applied between 40-100°F, the cartridge-based formula between 40-120°F, and the brushable between 60-100°F. Note: going above or below 72°F will affect the pot life and cure time of the material.

The thickness of the coating will depend on your desired application. For our hard coat products, we typically recommend applying a minimum of 60 mils to create a uniform film that will protect the piece. For more demanding applications where high impact is expected, such as outdoors, we recommend applying 60-120 mils to achieve the best results. Our brushable coatings have the best success at 100 mils and greater. The machinable hard coat should be applied thick enough that when machined, it is not reduced to less than 1/8 of an inch.

The amount of layers you must apply when using a hard coat depends on your desired coating thickness. If you are spraying larger projects, you may have to spray in multiple passes to coat the entire piece effectively.

If you want to reapply or add another coat over the existing material, stay within the recoat window. The high pressure and Qwik Spray formulas have a recoat window of 20 minutes, while the brushables have a recoat window of 4 hours. The machinable hard coat is unique and has a recoat window of 12 hours. If you want to apply another coat after the window passes, you will have to sand the material to ensure adhesion between subsequent coats. A primer can also be used to generate adhesion between layers.

Dry or cure time will depend on several factors. First of all, the application method plays a part in the speed of the coating. When applying a hard coat by brush, the pot life is increased to allow enough time for the material to be used before it cures. Because the pot life is longer, the time before the material will dry or cure is also longer.

The fastest version of our hard coats is VFI-6170 70 D Spray Hard Coat for high-pressure spray application. This material typically cures to touch in 20 seconds and cures to handle in 2-3 minutes, so you can sand, prime, and paint it much faster.

Temperature also affects cure time. This means temperature of the environment, application surface, and material. Higher temperatures will cause the material to cure faster, while cold temperatures will slow the cure time. We recommend spraying around room temperature (72°F).

Note: initial cure/dry time does not mean the coating will have obtained full physical properties. A complete cure will typically happen three days after application.

The hard coat is fully cured when it has obtained full physical properties. Our formulas typically reach these properties three days after application. Brushable hard coats may take a bit longer to reach these properties due to their formula.

If you’re having trouble with your hard coat curing, check out VFI’s tech piece for more information. 

Air bubbles typically occur in a polyurethane hard coat due to moisture. Urethane is a moisture-sensitive material, so if it reacts with a substantial amount of moisture in the environment, it will cause a foaming reaction that generates these air bubbles.

Make sure you’re working in a temperature-controlled, non-humid environment. We recommend applying the material around 72°F. Avoid using hard coatings over a wet or damp substrate. If you apply them over wood, it should contain less than 11% moisture.

Check out VFI’s tech piece to troubleshoot bubbling issues. 

Yes, VFI’s hard coat products are formulated to go on smoothly, but the texture may vary depending on the application method. Brush application may create a more textured feel and appearance due to brush strokes, which may require sanding depending on your desired finish. The Qwik Spray version may also have a slightly textured appearance because it’s a slowed formula, and the speed allows it to react more with the environment and moisture in the air, causing this effect. When the high pressure formula is not used, users might have to do more post-work to their pieces.

The amount of time the hard coats need after application before it will be ready for sanding will depend on several factors. Allow the coating enough time to cure to a desirable hardness for sanding. The formula will change the cure time, so brushable hard coats, because of their pot life, will need more time before sanding to cure. A high pressure hard coat can typically be sanded shortly after application since it cures in seconds (if you’re working in a temperature-controlled environment).

The amount of time after application that the hard coat needs before it will be ready for painting will depend on the formula and temperature. Allow the coating enough time to cure before you start painting. Due to brushable hard coats having a longer pot life, they will need more time to cure before painting. High pressure spray hard coats can typically be painted shortly after application since the coating cures in seconds (if you’re working in a temperature-controlled environment).

Hard coats do not have to be painted, but most applicators do paint over them to enhance the aesthetics of the overall piece. If they are not painted, a suitable UV stable top coat is required as they are not color-stable.

All VFI hard coats are designed to be primed and painted if desired. They will accept automotive primers and paints as well as architectural finishes. We ask that you do your own testing to see what works best for your project, but we have seen success whether customers use a primer or not between coatings and finishes.

Yes, VFI hard coats can be repaired if damage occurs to a newly applied or old coating. When repairing a hard coat, we recommend using VFI-6185 80 D Machinable Hard Coat or one of our brushable hard coats, whether the initial hard coating was applied by brush or spray.

To repair the hard coat, remove any remaining broken-off pieces in or around the damaged area. To ensure adhesion of the repair material, you must sand the existing coating around the damage. Once the damaged area is prepared, mix up your repair material by weight or volume. Fill the crack, hole, or damage to be level with the rest of the hard coated surface. Allow the patch to cure before sanding or painting it.

Check out VFI’s tech piece for more information on repairing hard coat.